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Halahakoon DC, Kaltenboeck A, Martens M, Geddes JG, Harmer CJ, Cowen P, Browning M. Pramipexole Enhances Reward Learning by Preserving Value Estimates. Biol Psychiatry 2024; 95:286-296. [PMID: 37330165 DOI: 10.1016/j.biopsych.2023.05.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 05/02/2023] [Accepted: 05/29/2023] [Indexed: 06/19/2023]
Abstract
BACKGROUND Dopamine D2-like agonists show promise as treatments for depression. They are thought to act by enhancing reward learning; however, the mechanisms by which they achieve this are not clear. Reinforcement learning accounts describe 3 distinct candidate mechanisms: increased reward sensitivity, increased inverse decision-temperature, and decreased value decay. As these mechanisms produce equivalent effects on behavior, arbitrating between them requires measurement of how expectations and prediction errors are altered. We characterized the effects of 2 weeks of the D2-like agonist pramipexole on reward learning and used functional magnetic resonance imaging measures of expectation and prediction error to assess which of these 3 mechanistic processes were responsible for the behavioral effects. METHODS Forty healthy volunteers (50% female) were randomized to 2 weeks of pramipexole (titrated to 1 mg/day) or placebo in a double-blind, between-subject design. Participants completed a probabilistic instrumental learning task before and after the pharmacological intervention, with functional magnetic resonance imaging data collected at the second visit. Asymptotic choice accuracy and a reinforcement learning model were used to assess reward learning. RESULTS Pramipexole increased choice accuracy in the reward condition with no effect on losses. Participants who received pramipexole had increased blood oxygen level-dependent response in the orbital frontal cortex during the expectation of win trials but decreased blood oxygen level-dependent response to reward prediction errors in the ventromedial prefrontal cortex. This pattern of results indicates that pramipexole enhances choice accuracy by reducing the decay of estimated values during reward learning. CONCLUSIONS The D2-like receptor agonist pramipexole enhances reward learning by preserving learned values. This is a plausible mechanism for pramipexole's antidepressant effect.
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Affiliation(s)
- Don Chamith Halahakoon
- Department of Psychiatry, University of Oxford, Oxford, United Kingdom; Oxford Health National Health Service Foundation Trust, Warneford Hospital, Oxford, United Kingdom
| | - Alexander Kaltenboeck
- Department of Psychiatry, University of Oxford, Oxford, United Kingdom; Clinical Division of Social Psychiatry, Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria
| | - Marieke Martens
- Department of Psychiatry, University of Oxford, Oxford, United Kingdom
| | - John G Geddes
- Department of Psychiatry, University of Oxford, Oxford, United Kingdom; Oxford Health National Health Service Foundation Trust, Warneford Hospital, Oxford, United Kingdom
| | - Catherine J Harmer
- Department of Psychiatry, University of Oxford, Oxford, United Kingdom; Oxford Health National Health Service Foundation Trust, Warneford Hospital, Oxford, United Kingdom
| | - Philip Cowen
- Department of Psychiatry, University of Oxford, Oxford, United Kingdom; Oxford Health National Health Service Foundation Trust, Warneford Hospital, Oxford, United Kingdom
| | - Michael Browning
- Department of Psychiatry, University of Oxford, Oxford, United Kingdom; Oxford Health National Health Service Foundation Trust, Warneford Hospital, Oxford, United Kingdom.
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Halahakoon DC, Browning M. Pramipexole for the Treatment of Depression: Efficacy and Mechanisms. Curr Top Behav Neurosci 2023. [PMID: 37982928 DOI: 10.1007/7854_2023_458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2023]
Abstract
Dopaminergic mechanisms are a plausible treatment target for patients with clinical depression but are relatively underexplored in conventional antidepressant medications. There is continuing interest in the potential antidepressant effects of the dopamine receptor agonist, pramipexole, with data from both case series and controlled trials indicating that this agent may produce benefit for patients with difficult-to-treat depression. Pramipexole's therapeutic utility in depression is likely to be expressed through alterations in reward mechanisms which are strongly influenced by dopamine pathways and are known to function abnormally in depressed patients. Our work in healthy participants using brain imaging in conjunction with computational modelling suggests that repeated pramipexole facilitates reward learning by inhibiting value decay. This mechanism needs to be confirmed in larger clinical trials in depressed patients. Such studies will also allow assessment of whether baseline performance in reward learning in depression predicts therapeutic response to pramipexole treatment.
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Affiliation(s)
- Don Chamith Halahakoon
- Department of Psychiatry, Warneford Hospital, Oxford, UK
- Oxford Health NHS Foundation Trust, Oxford, UK
| | - Michael Browning
- Department of Psychiatry, Warneford Hospital, Oxford, UK.
- Oxford Health NHS Foundation Trust, Oxford, UK.
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Darcey VL, Guo J, Courville AB, Gallagher I, Avery JA, Simmons WK, Ingeholm JE, Herscovitch P, Martin A, Hall KD. Dietary fat restriction affects brain reward regions in a randomized crossover trial. JCI Insight 2023; 8:e169759. [PMID: 37345661 PMCID: PMC10371234 DOI: 10.1172/jci.insight.169759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 05/10/2023] [Indexed: 06/23/2023] Open
Abstract
BACKGROUNDWeight-loss diets often target dietary fat or carbohydrates, macronutrients that are sensed via distinct gut-brain pathways and differentially affect peripheral hormones and metabolism. However, the effects of such diet changes on the human brain are unclear. METHODSWe investigated whether selective isocaloric reductions in dietary fat or carbohydrates altered dopamine D2/3 receptor binding potential (D2BP) and neural activity in brain-reward regions in response to visual food cues in 17 inpatient adults with obesity as compared with a eucaloric baseline diet using a randomized crossover design. RESULTSOn the fifth day of dietary fat restriction, but not carbohydrate restriction, both D2BP and neural activity to food cues were decreased in brain-reward regions. After the reduced-fat diet, ad libitum intake shifted toward foods high in both fat and carbohydrates. CONCLUSIONThese results suggest that dietary fat restriction increases tonic dopamine in brain-reward regions and affects food choice in ways that may hamper diet adherence. TRIAL REGISTRATIONClinicalTrials.gov NCT00846040 FUNDING. NIDDK 1ZIADK013037.
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Affiliation(s)
- Valerie L Darcey
- Integrative Physiology Section, National Institute of Diabetes & Digestive & Kidney Diseases, Bethesda, Maryland, USA
| | - Juen Guo
- Integrative Physiology Section, National Institute of Diabetes & Digestive & Kidney Diseases, Bethesda, Maryland, USA
| | - Amber B Courville
- Human Energy and Body Weight Regulation Core, National Institute of Diabetes & Digestive & Kidney Diseases, Bethesda, Maryland, USA
| | - Isabelle Gallagher
- Integrative Physiology Section, National Institute of Diabetes & Digestive & Kidney Diseases, Bethesda, Maryland, USA
| | - Jason A Avery
- Laboratory of Brain and Cognition, National Institute of Mental Health, Rockland, Maryland, USA
| | - W Kyle Simmons
- Biomedical Imaging Center, Oklahoma State University, Stillwater, Oklahoma, USA
| | - John E Ingeholm
- Laboratory of Brain and Cognition, National Institute of Mental Health, Rockland, Maryland, USA
| | - Peter Herscovitch
- Clinical Center Positron Emission Tomography Department, NIH, Bethesda, Maryland, USA
| | - Alex Martin
- Laboratory of Brain and Cognition, National Institute of Mental Health, Rockland, Maryland, USA
| | - Kevin D Hall
- Integrative Physiology Section, National Institute of Diabetes & Digestive & Kidney Diseases, Bethesda, Maryland, USA
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Katz BM, Walton LR, Houston KM, Cerri DH, Shih YYI. Putative neurochemical and cell type contributions to hemodynamic activity in the rodent caudate putamen. J Cereb Blood Flow Metab 2023; 43:481-498. [PMID: 36448509 PMCID: PMC10063835 DOI: 10.1177/0271678x221142533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 09/28/2022] [Accepted: 10/21/2022] [Indexed: 12/02/2022]
Abstract
Functional magnetic resonance imaging (fMRI) is widely used by researchers to noninvasively monitor brain-wide activity. The traditional assumption of a uniform relationship between neuronal and hemodynamic activity throughout the brain has been increasingly challenged. This relationship is now believed to be impacted by heterogeneously distributed cell types and neurochemical signaling. To date, most cell-type- and neurotransmitter-specific influences on hemodynamics have been examined within the cortex and hippocampus of rodent models, where glutamatergic signaling is prominent. However, neurochemical influences on hemodynamics are relatively unknown in largely GABAergic brain regions such as the rodent caudate putamen (CPu). Given the extensive contribution of CPu function and dysfunction to behavior, and the increasing focus on this region in fMRI studies, improved understanding of CPu hemodynamics could have broad impacts. Here we discuss existing findings on neurochemical contributions to hemodynamics as they may relate to the CPu with special consideration for how these contributions could originate from various cell types and circuits. We hope this review can help inform the direction of future studies as well as interpretation of fMRI findings in the CPu.
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Affiliation(s)
- Brittany M Katz
- Neuroscience Curriculum, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Center for Animal MRI, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Lindsay R Walton
- Center for Animal MRI, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Kaiulani M Houston
- Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Department of Neurology, New York University Grossman School of Medicine, New York, NY, USA
| | - Domenic H Cerri
- Center for Animal MRI, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Yen-Yu Ian Shih
- Neuroscience Curriculum, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Center for Animal MRI, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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Using pharmacological manipulations to study the role of dopamine in human reward functioning: A review of studies in healthy adults. Neurosci Biobehav Rev 2020; 120:123-158. [PMID: 33202256 DOI: 10.1016/j.neubiorev.2020.11.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 10/30/2020] [Accepted: 11/01/2020] [Indexed: 01/08/2023]
Abstract
Dopamine (DA) plays a key role in reward processing and is implicated in psychological disorders such as depression, substance use, and schizophrenia. The role of DA in reward processing is an area of highly active research. One approach to this question is drug challenge studies with drugs known to alter DA function. These studies provide good experimental control and can be performed in parallel in laboratory animals and humans. This review aimed to summarize results of studies using pharmacological manipulations of DA in healthy adults. 'Reward' is a complex process, so we separated 'phases' of reward, including anticipation, evaluation of cost and benefits of upcoming reward, execution of actions to obtain reward, pleasure in response to receiving a reward, and reward learning. Results indicated that i) DAergic drugs have different effects on different phases of reward; ii) the relationship between DA and reward functioning appears unlikely to be linear; iii) our ability to detect the effects of DAergic drugs varies depending on whether subjective, behavioral, imaging measures are used.
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Dopaminergic Modulation of Human Intertemporal Choice: A Diffusion Model Analysis Using the D2-Receptor Antagonist Haloperidol. J Neurosci 2020; 40:7936-7948. [PMID: 32948675 DOI: 10.1523/jneurosci.0592-20.2020] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 09/03/2020] [Accepted: 09/09/2020] [Indexed: 12/21/2022] Open
Abstract
The neurotransmitter dopamine is implicated in diverse functions, including reward processing, reinforcement learning, and cognitive control. The tendency to discount future rewards over time has long been discussed in the context of potential dopaminergic modulation. Here we examined the effect of a single dose of the D2 receptor antagonist haloperidol (2 mg) on temporal discounting in healthy female and male human participants. Our approach extends previous pharmacological studies in two ways. First, we applied combined temporal discounting drift diffusion models to examine choice dynamics. Second, we examined dopaminergic modulation of reward magnitude effects on temporal discounting. Hierarchical Bayesian parameter estimation revealed that the data were best accounted for by a temporal discounting drift diffusion model with nonlinear trialwise drift rate scaling. This model showed good parameter recovery, and posterior predictive checks revealed that it accurately reproduced the relationship between decision conflict and response times in individual participants. We observed reduced temporal discounting and substantially faster nondecision times under haloperidol compared with placebo. Discounting was steeper for low versus high reward magnitudes, but this effect was largely unaffected by haloperidol. Results were corroborated by model-free analyses and modeling via more standard approaches. We previously reported elevated caudate activation under haloperidol in this sample of participants, supporting the idea that haloperidol elevated dopamine neurotransmission (e.g., by blocking inhibitory feedback via presynaptic D2 auto-receptors). The present results reveal that this is associated with an augmentation of both lower-level (nondecision time) and higher-level (temporal discounting) components of the decision process.SIGNIFICANCE STATEMENT Dopamine is implicated in reward processing, reinforcement learning, and cognitive control. Here we examined the effects of a single dose of the D2 receptor antagonist haloperidol on temporal discounting and choice dynamics during the decision process. We extend previous studies by applying computational modeling using the drift diffusion model, which revealed that haloperidol reduced the nondecision time and reduced impulsive choice compared with placebo. These findings are compatible with a haloperidol-induced increase in striatal dopamine (e.g., because of a presynaptic mechanism). Our data provide novel insights into the contributions of dopamine to value-based decision-making and highlight how comprehensive model-based analyses using sequential sampling models can inform the effects of pharmacological modulation on choice processes.
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Masaki Y, Kashiwagi Y, Rokugawa T, Ito M, Iimori H, Abe K. Pharmacological MRI responses of raclopride in rats: The relationship with D2 receptor occupancy and cataleptic behavior. Synapse 2020; 74:e22180. [PMID: 32644234 DOI: 10.1002/syn.22180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 06/26/2020] [Accepted: 07/02/2020] [Indexed: 11/08/2022]
Abstract
Pharmacological magnetic resonance imaging (phMRI) allows the visualization of brain pharmacological effects of drugs using functional MRI (fMRI). phMRI can help us facilitate central nervous system (CNS) drug development. However, there have been few studies demonstrating the dose relationship of the fMRI response induced by CNS drugs to underlying target engagement or behavioral efficacy. To clarify these relationships, we examined receptor occupancy measurements using positron emission tomography (PET) (n = 3~5), fMRI (n = 5~8) and a cataleptic behavior (n = 6) with raclopride, a dopamine D2 receptor antagonist (8, 20, and 200 μg/kg) on Wistar rats. Dopamine D2 receptor occupancy was increased dose dependently by raclopride (41.8 ± 2.7%, 8 μg/kg; 64.9 ± 2.8%, 20 μg/kg; 83.1 ± 3.0%, 200 μg/kg). phMRI study revealed significant positive responses to raclopride at 200 μg/kg specifically in the striatum and nucleus accumbens, related to dopaminergic system. Slight fMRI responses were observed at 20 μg/kg in some areas corresponding to the striatum and nucleus accumbens. There were no noticeable fMRI responses at 8 μg/kg raclopride administration. Raclopride at 200 μg/kg significantly increased the cataleptic score, although, at 8 and 20 μg/kg, raclopride had no significant effects. These findings showed that raclopride-induced fMRI responses were observed at doses inducing cataleptic behavior and high D2 receptor occupancy, suggesting that phMRI can be useful for dose selection in clinical trial as an evaluation method of brain activity, which reflects behavioral responses induced by target engagements.
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Affiliation(s)
- Yukiko Masaki
- Imaging Biomarker, Biomarker R&D Department, Shionogi & Co., Ltd., Osaka, Japan
| | - Yuto Kashiwagi
- Imaging Biomarker, Biomarker R&D Department, Shionogi & Co., Ltd., Osaka, Japan
| | - Takemi Rokugawa
- Imaging Biomarker, Biomarker R&D Department, Shionogi & Co., Ltd., Osaka, Japan
| | - Miwa Ito
- Imaging Biomarker, Biomarker R&D Department, Shionogi & Co., Ltd., Osaka, Japan
| | - Hitoshi Iimori
- Research Laboratory for Development, Shionogi & Co., Ltd., Osaka, Japan
| | - Kohji Abe
- Imaging Biomarker, Biomarker R&D Department, Shionogi & Co., Ltd., Osaka, Japan
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Liu H, Luo Z, Gu J, Su Y, Flores H, Parsons SM, Zhou Y, Perlmutter JS, Tu Z. The impact of dopamine D 2-like agonist/antagonist on [ 18F]VAT PET measurement of VAChT in the brain of nonhuman primates. Eur J Pharm Sci 2020; 143:105152. [PMID: 31740395 PMCID: PMC6980745 DOI: 10.1016/j.ejps.2019.105152] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 10/15/2019] [Accepted: 11/14/2019] [Indexed: 01/11/2023]
Abstract
Vesicular acetylcholine transporter (VAChT) is a promising target for a PET measure of cholinergic deficits which contribute to cognitive impairments. Dopamine D2-like agonists and antagonists are frequently used in the elderly and could alter cholinergic function and VAChT level. Therefore, pretreatment with dopamine D2-like drugs may interfere with PET measures using [18F]VAT, a specific VAChT radioligand. Herein, we investigated the impact of dopaminergic D2-like antagonist/agonist on VAChT level in the brain of macaques using [18F]VAT PET. PET imaging studies were carried out on macaques at baseline or pretreatment conditions. For pretreatment, animals were injected using a VAChT inhibitor (-)-vesamicol, a D2-like antagonist (-)-eticlopride, and a D2-like agonist (-)-quinpirole, separately. (-)-Vesamicol was injected at escalating doses of 0.025, 0.05, 0.125, 0.25 and 0.35 mg/kg; (-)-eticlopride was injected at escalating doses of 0.01, 0.10 and 0.30 mg/kg; (-)-quinpirole was injected at escalating doses of 0.20, 0.30, and 0.50 mg/kg. PET data showed [18F]VAT uptake declined in a dose-dependent manner by (-)-vesamicol pretreatment, demonstrating [18F]VAT uptake is sensitive to reflect the availability of VAChT binding sites. Furthermore, (-)-eticlopride increased [18F]VAT striatal uptake in a dose-dependent manner, while (-)-quinpirole decreased its uptake, suggesting striatal VAChT levels can be regulated by D2-like drug administration. Our findings confirmed [18F]VAT offers a reliable tool to in vivo assess the availability of VAChT binding sites. More importantly, PET with [18F]VAT successfully quantified the impact of dopaminergic D2-like drugs on striatal VAChT level, suggesting [18F]VAT has great potential for investigating the interaction between dopaminergic and cholinergic systems in vivo.
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Affiliation(s)
- Hui Liu
- Department of Radiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Zonghua Luo
- Department of Radiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Jiwei Gu
- Department of Radiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Yi Su
- Department of Radiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Hubert Flores
- Department of Neurology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Stanley M Parsons
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA
| | - Yun Zhou
- Department of Radiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Joel S Perlmutter
- Department of Radiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Neurology, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Neuroscience, Physical Therapy and Occupational Therapy, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Zhude Tu
- Department of Radiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
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Lu H, Jaime S, Yang Y. Origins of the Resting-State Functional MRI Signal: Potential Limitations of the "Neurocentric" Model. Front Neurosci 2019; 13:1136. [PMID: 31708731 PMCID: PMC6819315 DOI: 10.3389/fnins.2019.01136] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Accepted: 10/08/2019] [Indexed: 02/06/2023] Open
Abstract
Resting-state functional connectivity (rsFC) is emerging as a research tool for systems and clinical neuroscience. The mechanism underlying resting-state functional MRI (rsfMRI) signal, however, remains incompletely understood. A widely held assumption is that the spontaneous fluctuations in blood oxygenation level-dependent (BOLD) signal reflect ongoing neuronal processes (herein called “neurocentric” model). In support of this model, evidence from human and animal studies collectively reveals that the spatial synchrony of spontaneously occurring electrophysiological signal recapitulates BOLD rsFC networks. Two recent experiments from independent labs designed to specifically examine neuronal origins of rsFC, however, suggest that spontaneously occurring neuronal events, as assessed by multiunit activity or local field potential (LFP), although statistically significant, explain only a small portion (∼10%) of variance in resting-state BOLD fluctuations. These two studies, although each with its own limitations, suggest that the spontaneous fluctuations in rsfMRI, may have complex cellular origins, and the “neurocentric” model may not apply to all brain regions.
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Affiliation(s)
- Hanbing Lu
- Neuroimaging Research Branch, National Institute on Drug Abuse (NIDA) Intramural Research Program, National Institutes of Health, Bethesda, MD, United States
| | - Saul Jaime
- Division of Pharmacology & Toxicology, College of Pharmacy, The University of Texas at Austin, Austin, TX, United States.,Waggoner Center for Alcohol & Addiction Research, The University of Texas at Austin, Austin, TX, United States
| | - Yihong Yang
- Neuroimaging Research Branch, National Institute on Drug Abuse (NIDA) Intramural Research Program, National Institutes of Health, Bethesda, MD, United States
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Dow-Edwards D, MacMaster FP, Peterson BS, Niesink R, Andersen S, Braams BR. Experience during adolescence shapes brain development: From synapses and networks to normal and pathological behavior. Neurotoxicol Teratol 2019; 76:106834. [PMID: 31505230 DOI: 10.1016/j.ntt.2019.106834] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 07/27/2019] [Accepted: 09/06/2019] [Indexed: 12/20/2022]
Abstract
Adolescence is a period of dramatic neural reorganization creating a period of vulnerability and the possibility for the development of psychopathology. The maturation of various neural circuits during adolescence depends, to a large degree, on one's experiences both physical and psychosocial. This occurs through a process of plasticity which is the structural and functional adaptation of the nervous system in response to environmental demands, physiological changes and experiences. During adolescence, this adaptation proceeds upon a backdrop of structural and functional alterations imparted by genetic and epigenetic factors and experiences both prior to birth and during the postnatal period. Plasticity entails an altering of connections between neurons through long-term potentiation (LTP) (which alters synaptic efficiency), synaptogenesis, axonal sprouting, dendritic remodeling, neurogenesis and recruitment (Skaper et al., 2017). Although most empirical evidence for plasticity derives from studies of the sensory systems, recent studies have suggested that during adolescence, social, emotional, and cognitive experiences alter the structure and function of the networks subserving these domains of behavior. Each of these neural networks exhibits heightened vulnerability to experience-dependent plasticity during the sensitive periods which occur in different circuits and different brain regions at specific periods of development. This report will summarize some examples of adaptation which occur during adolescence and some evidence that the adolescent brain responds differently to stimuli compared to adults and children. This symposium, "Experience during adolescence shapes brain development: from synapses and networks to normal and pathological behavior" occurred during the Developmental Neurotoxicology Society/Teratology Society Annual Meeting in Clearwater Florida, June 2018. The sections will describe the maturation of the brain during adolescence as studied using imaging technologies, illustrate how plasticity shapes the structure of the brain using examples of pathological conditions such as Tourette's' syndrome and attention deficit hyperactivity disorder, and a review of the key molecular systems involved in this plasticity and how some commonly abused substances alter brain development. The role of stimulants used in the treatment of attention deficit hyperactivity disorder (ADHD) in the plasticity of the reward circuit is then described. Lastly, clinical data promoting an understanding of peer-influences on risky behavior in adolescents provides evidence for the complexity of the roles that peers play in decision making, a phenomenon different from that in the adult. Imaging studies have revealed that activation of the social network by the presence of peers at times of decision making is unique in the adolescent. Since normal brain development relies on experiences which alter the functional and structural connections between cells within circuits and networks to ultimately alter behavior, readers can be made aware of the myriad of ways normal developmental processes can be hijacked. The vulnerability of developing adolescent brain places the adolescent at risk for the development of a life time of abnormal behaviors and mental disorders.
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Affiliation(s)
- Diana Dow-Edwards
- Department of Physiology & Pharmacology, State University of New York, Downstate Medical Center, Brooklyn, NY, United States of America.
| | - Frank P MacMaster
- Departments of Psychiatry & Pediatrics, University of Calgary, Addiction and Mental Health Strategic Clinical Network, Calgary, Alberta, Canada
| | - Bradley S Peterson
- Children's Hospital Los Angeles, The Keck School of Medicine at the University of Southern California, Los Angeles, CA, United States of America
| | - Raymond Niesink
- Trimbos Institute, Netherlands Institute of Mental Health and Addiction, Utrecht, the Netherlands; Faculty of Management, Science and Technology, School of Science, Open University of the Netherlands, Heerlen, the Netherlands
| | - Susan Andersen
- McLean Hospital, Department of Psychiatry, Harvard Medical School, Boston, MA, United States of America
| | - B R Braams
- Department of Psychology, Center for Brain Science, Harvard University, Cambridge, MA, United States of America
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11
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Dopamine Enhances Item Novelty Detection via Hippocampal and Associative Recall via Left Lateral Prefrontal Cortex Mechanisms. J Neurosci 2019; 39:7920-7933. [PMID: 31405927 DOI: 10.1523/jneurosci.0495-19.2019] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 07/04/2019] [Accepted: 07/16/2019] [Indexed: 11/21/2022] Open
Abstract
The involvement of fronto-striatal circuits in item and associative memory retrieval as well as in the stabilization of memories by retrieval practice suggests that both retrieval and re-encoding of stored memories might rely on dopaminergic mechanisms in humans. We tested these hypotheses in a placebo-controlled pharmacological fMRI study using 2 mg of the D2 antagonist haloperidol administered acutely before a cued associative recall task of previously encoded picture-word pairs in 53 healthy humans of both sexes. The cued associative recall was moreover repeated 3 d later outside the scanner without pharmacological intervention. Dopaminergic modulation significantly improved associative recall performance and recognition accuracy of verbal items. Moreover, we observed a significant dopamine effect on re-encoding in terms of increased specificity of associative memories from the first to the second cued associative recall. Better association memory under haloperidol was linked with higher activity in the left lateral prefrontal cortex and right parietal cortex, suggesting that dopamine facilitates associative retrieval through increased recruitment of frontoparietal monitoring processes. In contrast, improved recognition of verbal items under haloperidol was reflected by enhanced novelty detection in the hippocampus and increased activity in saliency networks. Together, these results show distinct but concomitant positive effects of dopamine on associative recall and item recognition and suggest that the specificity of associative recall through re-encoding mechanisms is likewise augmented by dopamine.SIGNIFICANCE STATEMENT Although the neurotransmitter dopamine has been linked with learning and memory for a long time, dopaminergic effects on item recognition in humans were demonstrated only recently. The involvement of fronto-striatal monitoring processes in association retrieval suggests that associative memory might be particularly affected by dopamine. Moreover, fronto-striatal dopaminergic signals have been hypothesized to determine the updating and re-encoding of previously retrieved memories. We here demonstrate clear facilitative effects of dopamine on associative recall and item recognition mediated by prefrontal and hippocampal mechanisms respectively. Additionally, effects on re-encoding were reflected by increased specificity of associative memories. These results augment our understanding of dopaminergic processes in episodic memory retrieval and offer new perspectives on memory impairments in dopamine-related disorders and their treatment.
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12
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Clos M, Bunzeck N, Sommer T. Dopamine is a double-edged sword: dopaminergic modulation enhances memory retrieval performance but impairs metacognition. Neuropsychopharmacology 2019; 44:555-563. [PMID: 30356095 PMCID: PMC6333779 DOI: 10.1038/s41386-018-0246-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 10/09/2018] [Accepted: 10/12/2018] [Indexed: 12/30/2022]
Abstract
While memory encoding and consolidation processes have been linked with dopaminergic signaling for a long time, the role of dopamine in episodic memory retrieval remained mostly unexplored. Based on previous observations of striatal activity during memory retrieval, we used pharmacological functional magnetic resonance imaging to investigate the effects of dopamine on retrieval performance and metacognitive memory confidence in healthy humans. Dopaminergic modulation by the D2 antagonist haloperidol administered acutely during the retrieval phase improved recognition accuracy of previously learned pictures significantly and was associated with increased activity in the substantia nigra/ventral tegmental area, locus coeruleus, hippocampus, and amygdala during retrieval. In contrast, confidence for new decisions was impaired by unsystematically increased activity of the striatum across confidence levels and restricted range of responsiveness in frontostriatal networks under haloperidol. These findings offer new insights into the mechanisms underlying memory retrieval and metacognition and provide a broader perspective on the presence of memory problems in dopamine-related diseases and the treatment of memory disorders.
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Affiliation(s)
- Mareike Clos
- Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
| | - Nico Bunzeck
- 0000 0001 2180 3484grid.13648.38Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany ,0000 0001 0057 2672grid.4562.5Institute of Psychology I, University of Lübeck, Lübeck, Germany
| | - Tobias Sommer
- 0000 0001 2180 3484grid.13648.38Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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13
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Sander CY, Mandeville JB, Wey HY, Catana C, Hooker JM, Rosen BR. Effects of flow changes on radiotracer binding: Simultaneous measurement of neuroreceptor binding and cerebral blood flow modulation. J Cereb Blood Flow Metab 2019; 39:131-146. [PMID: 28816571 PMCID: PMC6311667 DOI: 10.1177/0271678x17725418] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The potential effects of changes in blood flow on the delivery and washout of radiotracers has been an ongoing question in PET bolus injection studies. This study provides practical insight into this topic by experimentally measuring cerebral blood flow (CBF) and neuroreceptor binding using simultaneous PET/MRI. Hypercapnic challenges (7% CO2) were administered to non-human primates in order to induce controlled increases in CBF, measured with pseudo-continuous arterial spin labeling. Simultaneously, dopamine D2/D3 receptor binding of [11C]raclopride or [18F]fallypride was monitored with dynamic PET. Experiments showed that neither time activity curves nor quantification of binding through binding potentials ( BPND) were measurably affected by CBF increases, which were larger than two-fold. Simulations of experimental procedures showed that even large changes in CBF should have little effect on the time activity curves of radiotracers, given a set of realistic assumptions. The proposed method can be applied to experimentally assess the flow sensitivity of other radiotracers. Results demonstrate that CBF changes, which often occur due to behavioral tasks or pharmacological challenges, do not affect PET [11C]raclopride or [18F]fallypride binding studies and their quantification. The results from this study suggest flow effects may have limited impact on many PET neuroreceptor tracers with similar properties.
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Affiliation(s)
- Christin Y Sander
- 1 Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA.,2 Harvard Medical School, Boston, MA, USA
| | - Joseph B Mandeville
- 1 Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA.,2 Harvard Medical School, Boston, MA, USA
| | - Hsiao-Ying Wey
- 1 Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA.,2 Harvard Medical School, Boston, MA, USA
| | - Ciprian Catana
- 1 Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA.,2 Harvard Medical School, Boston, MA, USA
| | - Jacob M Hooker
- 1 Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA.,2 Harvard Medical School, Boston, MA, USA
| | - Bruce R Rosen
- 1 Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA.,2 Harvard Medical School, Boston, MA, USA.,3 Health Sciences and Technology, Harvard-MIT, Cambridge, MA, USA
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14
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Iriah SC, Trivedi M, Kenkel W, Grant SE, Moore K, Yee JR, Madularu D, Kulkarni P, Ferris CF. Oxycodone Exposure: A Magnetic Resonance Imaging Study in Response to Acute and Chronic Oxycodone Treatment in Rats. Neuroscience 2018; 398:88-101. [PMID: 30550747 DOI: 10.1016/j.neuroscience.2018.11.042] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Revised: 11/26/2018] [Accepted: 11/28/2018] [Indexed: 11/16/2022]
Abstract
The present study was designed to use blood-oxygen-level dependent (BOLD) imaging to "fingerprint" the change in activity in response to oxycodone (OXY) in drug naïve rats before and after repeated exposure to OXY. It was hypothesized that repeated exposure to OXY would initiate adaptive changes in brain organization that would be reflected in an altered response to opioid exposure. Male rats exposed to OXY repeatedly showed conditioned place preference, evidence of drug-seeking behavior and putative neuroadaptation. As these studies were done on awake rats we discovered it was not possible to image rats continuously exposed to OXY due to motion artifact judged to be withdrawal while in the scanner. To circumvent this problem manganese-enhanced MRI (MEMRI) was used to map the distributed integrated activity pattern resulting from continuous OXY exposure. Rats were administered OXY (2.5 mg/kg, i.p.) during image acquisition and changes in BOLD signal intensity were recorded and the activation and deactivation of integrated neural circuits involved in olfaction and motivation were identified. Interestingly, the circuitry of the mesencephalic dopaminergic system showed little activity to the first exposure of OXY. In the MEMRI study, rats received OXY treatments (2.5 mg/kg, twice daily) for four consecutive days following intraventricular MnCl2. Under isoflurane anesthesia, T1-weighted images were acquired and subsequently analyzed showing activity in the forebrain limbic system, ventral striatum, accumbens, amygdala and hippocampus. These results show brain activity is markedly different when OXY is presented to drug naïve rats versus rats with prior, repeated exposure to drug.
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Affiliation(s)
- Sade C Iriah
- Northeastern Univ., Center for Translational NeuroImaging, Boston, MA, USA
| | - Malav Trivedi
- NOVA Southeastern University, Ft. Lauderdale, FL, USA
| | - William Kenkel
- The Kinsey Institute, Indiana University, Bloomington, IN, USA
| | - Simone E Grant
- Northeastern Univ., Center for Translational NeuroImaging, Boston, MA, USA
| | - Kelsey Moore
- Northeastern Univ., Center for Translational NeuroImaging, Boston, MA, USA
| | - Jason R Yee
- Northeastern Univ., Center for Translational NeuroImaging, Boston, MA, USA
| | - Dan Madularu
- Northeastern Univ., Center for Translational NeuroImaging, Boston, MA, USA; Douglas Hospital, McGill University, Montreal, QC, Canada; Carleton University, Ottawa, ON, Canada
| | - Praveen Kulkarni
- Northeastern Univ., Center for Translational NeuroImaging, Boston, MA, USA
| | - Craig F Ferris
- Northeastern Univ., Center for Translational NeuroImaging, Boston, MA, USA.
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Clos M, Sommer T, Schneider SL, Rose M. Enhanced transformation of incidentally learned knowledge into explicit memory by dopaminergic modulation. PLoS One 2018; 13:e0199013. [PMID: 29902226 PMCID: PMC6002242 DOI: 10.1371/journal.pone.0199013] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 05/30/2018] [Indexed: 01/07/2023] Open
Abstract
During incidental learning statistical regularities are extracted from the environment without the intention to learn. Acquired implicit memory of these regularities can affect behavior in the absence of awareness. However, conscious insight in the underlying regularities can also develop during learning. Such emergence of explicit memory is an important learning mechanism that is assumed to involve prediction errors in the striatum and to be dopamine-dependent. Here we directly tested this hypothesis by manipulating dopamine levels during incidental learning in a modified serial reaction time task (SRTT) featuring a hidden regular sequence of motor responses in a placebo-controlled between-group study. Awareness for the sequential regularity was subsequently assessed using cued generation and additionally verified using free recall. The results demonstrated that dopaminergic modulation nearly doubled the amount of explicit sequence knowledge emerged during learning in comparison to the placebo group. This strong effect clearly argues for a causal role of dopamine-dependent processing for the development of awareness for sequential regularities during learning.
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Affiliation(s)
- Mareike Clos
- Department for Systems Neuroscience, University Medical Center Hamburg Eppendorf, Martinistr. 52, Hamburg, Germany
| | - Tobias Sommer
- Department for Systems Neuroscience, University Medical Center Hamburg Eppendorf, Martinistr. 52, Hamburg, Germany
| | - Signe L. Schneider
- Department for Systems Neuroscience, University Medical Center Hamburg Eppendorf, Martinistr. 52, Hamburg, Germany
| | - Michael Rose
- Department for Systems Neuroscience, University Medical Center Hamburg Eppendorf, Martinistr. 52, Hamburg, Germany
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16
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Barry RL, Byun NE, Williams JM, Siuta MA, Tantawy MN, Speed NK, Saunders C, Galli A, Niswender KD, Avison MJ. Brief exposure to obesogenic diet disrupts brain dopamine networks. PLoS One 2018; 13:e0191299. [PMID: 29698491 PMCID: PMC5919534 DOI: 10.1371/journal.pone.0191299] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 01/02/2018] [Indexed: 11/26/2022] Open
Abstract
Objective We have previously demonstrated that insulin signaling, through the downstream signaling kinase Akt, is a potent modulator of dopamine transporter (DAT) activity, which fine-tunes dopamine (DA) signaling at the synapse. This suggests a mechanism by which impaired neuronal insulin receptor signaling, a hallmark of diet-induced obesity, may contribute to impaired DA transmission. We tested whether a short-term (two-week) obesogenic high-fat (HF) diet could reduce striatal Akt activity, a marker of central insulin, receptor signaling and blunt striatal and dopaminergic network responsiveness to amphetamine (AMPH). Methods We examined the effects of a two-week HF diet on striatal DAT activity in rats, using AMPH as a probe in a functional magnetic resonance imaging (fMRI) assay, and mapped the disruption in AMPH-evoked functional connectivity between key dopaminergic targets and their projection areas using correlation and permutation analyses. We used phosphorylation of the Akt substrate GSK3α in striatal extracts as a measure of insulin receptor signaling. Finally, we confirmed the impact of HF diet on striatal DA D2 receptor (D2R) availability using [18F]fallypride positron emission tomography (PET). Results We found that rats fed a HF diet for only two weeks have reductions in striatal Akt activity, a marker of decreased striatal insulin receptor signaling and blunted striatal responsiveness to AMPH. HF feeding also reduced interactions between elements of the mesolimbic (nucleus accumbens–anterior cingulate) and sensorimotor circuits (caudate/putamen–thalamus–sensorimotor cortex) implicated in hedonic feeding. D2R availability was reduced in HF-fed animals. Conclusion These studies support the hypothesis that central insulin signaling and dopaminergic neurotransmission are already altered after short-term HF feeding. Because AMPH induces DA efflux and brain activation, in large part via DAT, these findings suggest that blunted central nervous system insulin receptor signaling through a HF diet can impair DA homeostasis, thereby disrupting cognitive and reward circuitry involved in the regulation of hedonic feeding.
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Affiliation(s)
- Robert L. Barry
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Nellie E. Byun
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- * E-mail:
| | - Jason M. Williams
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Michael A. Siuta
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Mohammed N. Tantawy
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Nicole K. Speed
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Christine Saunders
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Aurelio Galli
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Vanderbilt Brain Institute, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Department of Psychiatry, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Kevin D. Niswender
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Vanderbilt Brain Institute, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Tennessee Valley Healthcare System, Nashville, Tennessee, United States of America
| | - Malcolm J. Avison
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Vanderbilt Brain Institute, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
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17
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Bruinsma TJ, Sarma VV, Oh Y, Jang DP, Chang SY, Worrell GA, Lowe VJ, Jo HJ, Min HK. The Relationship Between Dopamine Neurotransmitter Dynamics and the Blood-Oxygen-Level-Dependent (BOLD) Signal: A Review of Pharmacological Functional Magnetic Resonance Imaging. Front Neurosci 2018; 12:238. [PMID: 29692706 PMCID: PMC5902685 DOI: 10.3389/fnins.2018.00238] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 03/27/2018] [Indexed: 11/13/2022] Open
Abstract
Functional magnetic resonance imaging (fMRI) is widely used in investigations of normal cognition and brain disease and in various clinical applications. Pharmacological fMRI (pharma-fMRI) is a relatively new application, which is being used to elucidate the effects and mechanisms of pharmacological modulation of brain activity. Characterizing the effects of neuropharmacological agents on regional brain activity using fMRI is challenging because drugs modulate neuronal function in a wide variety of ways, including through receptor agonist, antagonist, and neurotransmitter reuptake blocker events. Here we review current knowledge on neurotransmitter-mediated blood-oxygen-level dependent (BOLD) fMRI mechanisms as well as recently updated methodologies aimed at more fully describing the effects of neuropharmacologic agents on the BOLD signal. We limit our discussion to dopaminergic signaling as a useful lens through which to analyze and interpret neurochemical-mediated changes in the hemodynamic BOLD response. We also discuss the need for future studies that use multi-modal approaches to expand the understanding and application of pharma-fMRI.
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Affiliation(s)
- Tyler J Bruinsma
- Department of Radiology, College of Medicine, Mayo Clinic, Rochester, MN, United States
| | - Vidur V Sarma
- Department of Radiology, College of Medicine, Mayo Clinic, Rochester, MN, United States.,Department of Pharmaceutics and Brain Barriers Research Center, College of Pharmacy, University of Minnesota, Minneapolis, MN, United States
| | - Yoonbae Oh
- Department of Biomedical Engineering, Hanyang University, Seoul, South Korea.,Department of Neurologic Surgery, College of Medicine, Mayo Clinic, Rochester, MN, United States
| | - Dong Pyo Jang
- Department of Biomedical Engineering, Hanyang University, Seoul, South Korea
| | - Su-Youne Chang
- Department of Neurologic Surgery, College of Medicine, Mayo Clinic, Rochester, MN, United States.,Departments of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States
| | - Greg A Worrell
- Department of Neurology, College of Medicine, Mayo Clinic, Rochester, MN, United States
| | - Val J Lowe
- Department of Radiology, College of Medicine, Mayo Clinic, Rochester, MN, United States
| | - Hang Joon Jo
- Department of Neurologic Surgery, College of Medicine, Mayo Clinic, Rochester, MN, United States.,Department of Neurology, College of Medicine, Mayo Clinic, Rochester, MN, United States
| | - Hoon-Ki Min
- Department of Radiology, College of Medicine, Mayo Clinic, Rochester, MN, United States.,Department of Neurologic Surgery, College of Medicine, Mayo Clinic, Rochester, MN, United States.,Departments of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States
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18
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Choi JK, Lim G, Chen YCI, Jenkins BG. Abstinence to chronic methamphetamine switches connectivity between striatal, hippocampal and sensorimotor regions and increases cerebral blood volume response. Neuroimage 2018. [PMID: 29518566 DOI: 10.1016/j.neuroimage.2018.02.059] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023] Open
Abstract
Methamphetamine (meth), and other psychostimulants such as cocaine, present a persistent problem for society with chronic users being highly prone to relapse. We show, in a chronic methamphetamine administration model, that discontinuation of drug for more than a week produces much larger changes in overall meth-induced brain connectivity and cerebral blood volume (CBV) response than changes that occur immediately following meth administration. Areas showing the largest changes were hippocampal, limbic striatum and sensorimotor cortical regions as well as brain stem areas including the pedunculopontine tegmentum (PPTg) and pontine nuclei - regions known to be important in mediating reinstatement of drug-taking after abstinence. These changes occur concomitantly with behavioral sensitization and appear to be mediated through increases in dopamine D1 and D3 and decreases in D2 receptor protein and mRNA expression. We further identify a novel region of dorsal caudate/putamen, with a low density of calbindin neurons, that has an opposite hemodynamic response to meth than the rest of the caudate/putamen and accumbens and shows very strong correlation with dorsal CA1 and CA3 hippocampus. This correlation switches following meth abstinence from CA1/CA3 to strong connections with ventral hippocampus (ventral subiculum) and nucleus accumbens. These data provide novel evidence for temporal alterations in brain connectivity where chronic meth can subvert hippocampal - striatal interactions from cognitive control regions to regions that mediate drug reinstatement. Our results also demonstrate that the signs and magnitudes of the induced CBV changes following challenge with meth or a D3-preferring agonist are a complementary read out of the relative changes that occur in D1, D2 and D3 receptors using protein or mRNA levels.
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Affiliation(s)
- Ji-Kyung Choi
- A.A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, 02129, USA.
| | - Grewo Lim
- Department of Anesthesiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, 02129, USA
| | - Yin-Ching Iris Chen
- A.A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, 02129, USA
| | - Bruce G Jenkins
- A.A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, 02129, USA.
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Sander CY, Hesse S. News and views on in-vivo imaging of neurotransmission using PET and MRI. THE QUARTERLY JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING : OFFICIAL PUBLICATION OF THE ITALIAN ASSOCIATION OF NUCLEAR MEDICINE (AIMN) [AND] THE INTERNATIONAL ASSOCIATION OF RADIOPHARMACOLOGY (IAR), [AND] SECTION OF THE SOCIETY OF... 2017; 61:414-428. [PMID: 28750497 PMCID: PMC5916779 DOI: 10.23736/s1824-4785.17.03019-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Molecular neuroimaging with PET is an integrated tool in psychiatry research and drug-development for as long as this modality has been available, in particular for studying neurotransmission and endogenous neurotransmitter release. Pharmacologic, behavioral and other types of challenges are currently applied to induce changes in neurochemical levels that can be inferred through their effects on changes in receptor binding and related outcome measures. Based on the availability of tracers that are sensitive for measuring neurotransmitter release these experiments have focused on the brain's dopamine system, while recent developments have extended those studies to other targets such as the serotonin or choline system. With the introduction of hybrid, truly simultaneous PET/MRI systems, in-vivo imaging of the dynamics of neuroreceptor signal transmission in the brain using PET and functional MRI (fMRI) has become possible. fMRI has the ability to provide information about the effects of receptor function that are complementary to the PET measurement. Dynamic acquisition of both PET and fMRI signals enables not only an in-vivo real-time assessment of neurotransmitter or drug binding to receptors but also dynamic receptor adaptations and receptor-specific neurotransmission. While fMRI temporal resolution is comparatively fast in relation to PET, the timescale of observable biological processes is highly dependent on the kinetics of radiotracers and study design. Overall, the combination of the specificity of PET radiotracers to neuroreceptors, fMRI signal as a functional readout and integrated study design promises to expand our understanding of the location, propagation and connections of brain activity in health and disease.
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Affiliation(s)
- Christin Y Sander
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA -
- Harvard Medical School, Boston, MA, USA -
| | - Swen Hesse
- Department of Nuclear Medicine, University of Leipzig, Leipzig, Germany
- Integrated Treatment and Research Center (IFB) Adiposity Diseases, Leipzig University Medical Center, Leipzig, Germany
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20
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Unexpected global impact of VTA dopamine neuron activation as measured by opto-fMRI. Mol Psychiatry 2017; 22:585-594. [PMID: 27457809 PMCID: PMC5269559 DOI: 10.1038/mp.2016.102] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Revised: 04/27/2016] [Accepted: 05/02/2016] [Indexed: 12/17/2022]
Abstract
Dopamine neurons in the ventral tegmental area (VTA) are strongly implicated in cognitive and affective processing as well as in psychiatric disorders, including schizophrenia, depression, attention-deficit hyperactivity disorder and substance abuse disorders. In human studies, dopamine-related functions are routinely assessed using functional magnetic resonance imaging (fMRI) measures of blood oxygenation-level-dependent (BOLD) signals during the performance of dopamine-dependent tasks. There is, however, a critical void in our knowledge about whether and how activation of VTA dopamine neurons specifically influences regional or global fMRI signals. Here, we used optogenetics in Th::Cre rats to selectively stimulate VTA dopamine neurons while simultaneously measuring global hemodynamic changes using BOLD and cerebral blood volume-weighted (CBVw) fMRI. Phasic activation of VTA dopamine neurons increased BOLD and CBVw fMRI signals in VTA-innervated limbic regions, including the ventral striatum (nucleus accumbens). Surprisingly, basal ganglia regions that receive sparse or no VTA dopaminergic innervation, including the dorsal striatum and the globus pallidus, were also activated. In fact, the most prominent fMRI signal increase in the forebrain was observed in the dorsal striatum that is not traditionally associated with VTA dopamine neurotransmission. These data establish causation between phasic activation of VTA dopamine neurons and global fMRI signals. They further suggest that mesolimbic and non-limbic basal ganglia dopamine circuits are functionally connected and thus provide a potential novel framework for understanding dopamine-dependent functions and interpreting data obtained from human fMRI studies.
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21
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Sahlholm K, Ielacqua GD, Xu J, Jones LA, Schlegel F, Mach RH, Rudin M, Schroeter A. The role of beta-arrestin2 in shaping fMRI BOLD responses to dopaminergic stimulation. Psychopharmacology (Berl) 2017; 234:2019-2030. [PMID: 28382543 PMCID: PMC5486931 DOI: 10.1007/s00213-017-4609-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Accepted: 03/18/2017] [Indexed: 01/11/2023]
Abstract
RATIONALE The dopamine D2 receptor (D2R) couples to inhibitory Gi/o proteins and is targeted by antipsychotic and antiparkinsonian drugs. Beta-arrestin2 binds to the intracellular regions of the agonist-occupied D2R to terminate G protein activation and promote internalization, but also to initiate downstream signaling cascades which have been implicated in psychosis. Functional magnetic resonance imaging (fMRI) has proven valuable for measuring dopamine receptor-mediated changes in neuronal activity, and might enable beta-arrestin2 function to be studied in vivo. OBJECTIVES The present study examined fMRI blood oxygenation level dependent (BOLD) signal changes elicited by a dopamine agonist in wild-type (WT) and beta-arrestin2 knockout (KO) mice, to investigate whether genetic deletion of beta-arrestin2 prolongs or otherwise modifies D2R-dependent responses. METHODS fMRI BOLD data were acquired on a 9.4 T system. During scans, animals received 0.2 mg/kg apomorphine, i.v. In a subset of experiments, animals were pretreated with 2 mg/kg of the D2R antagonist, eticlopride. RESULTS Following apomorphine administration, BOLD signal decreases were observed in caudate/putamen of WT and KO animals. The time course of response decay in caudate/putamen was significantly slower in KO vs. WT animals. In cingulate cortex, an initial BOLD signal decrease was followed by a positive response component in WT but not in KO animals. Eticlopride pretreatment significantly reduced apomorphine-induced BOLD signal changes. CONCLUSIONS The prolonged striatal response decay rates in KO animals might reflect impaired D2R desensitization, consistent with the known function of beta-arrestin2. Furthermore, the apomorphine-induced positive response component in cingulate cortex may depend on beta-arrestin2 signaling downstream of D2R.
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Affiliation(s)
- Kristoffer Sahlholm
- Institute for Biomedical Engineering, University and ETH Zurich, Wolfgang-Pauli-Str. 27, 8093, Zurich, Switzerland. .,Department of Radiology, Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 S. Kingshighway Blvd, St. Louis, MO, 63110, USA. .,Department of Neuroscience, Karolinska Institutet, Retzius väg 8, SE-171 77, Stockholm, Sweden.
| | - Giovanna D. Ielacqua
- 0000 0001 2156 2780grid.5801.cInstitute for Biomedical Engineering, University and ETH Zurich, Wolfgang-Pauli-Str. 27, 8093 Zurich, Switzerland
| | - Jinbin Xu
- 0000 0001 2355 7002grid.4367.6Department of Radiology, Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 S. Kingshighway Blvd, St. Louis, MO 63110 USA
| | - Lynne A. Jones
- 0000 0001 2355 7002grid.4367.6Department of Radiology, Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 S. Kingshighway Blvd, St. Louis, MO 63110 USA
| | - Felix Schlegel
- 0000 0001 2156 2780grid.5801.cInstitute for Biomedical Engineering, University and ETH Zurich, Wolfgang-Pauli-Str. 27, 8093 Zurich, Switzerland
| | - Robert H. Mach
- 0000 0004 1936 8972grid.25879.31Department of Radiology, Perelman School of Medicine, University of Pennsylvania, 231 S. 34th St, Philadelphia, PA 19104 USA
| | - Markus Rudin
- 0000 0001 2156 2780grid.5801.cInstitute for Biomedical Engineering, University and ETH Zurich, Wolfgang-Pauli-Str. 27, 8093 Zurich, Switzerland ,0000 0001 2156 2780grid.5801.cNeuroscience Center Zurich, University and ETH Zurich, Winterthurer-Str. 190, 8057 Zurich, Switzerland ,0000 0004 1937 0650grid.7400.3Institute of Pharmacology and Toxicology, University of Zurich, Winterthurer-Str. 190, 8057 Zurich, Switzerland
| | - Aileen Schroeter
- 0000 0001 2156 2780grid.5801.cInstitute for Biomedical Engineering, University and ETH Zurich, Wolfgang-Pauli-Str. 27, 8093 Zurich, Switzerland ,0000 0001 2156 2780grid.5801.cNeuroscience Center Zurich, University and ETH Zurich, Winterthurer-Str. 190, 8057 Zurich, Switzerland
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Moore K, Madularu D, Iriah S, Yee JR, Kulkarni P, Darcq E, Kieffer BL, Ferris CF. BOLD Imaging in Awake Wild-Type and Mu-Opioid Receptor Knock-Out Mice Reveals On-Target Activation Maps in Response to Oxycodone. Front Neurosci 2016; 10:471. [PMID: 27857679 PMCID: PMC5094148 DOI: 10.3389/fnins.2016.00471] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 10/03/2016] [Indexed: 02/06/2023] Open
Abstract
Blood oxygen level dependent (BOLD) imaging in awake mice was used to identify differences in brain activity between wild-type, and Mu (μ) opioid receptor knock-outs (MuKO) in response to oxycodone (OXY). Using a segmented, annotated MRI mouse atlas and computational analysis, patterns of integrated positive and negative BOLD activity were identified across 122 brain areas. The pattern of positive BOLD showed enhanced activation across the brain in WT mice within 15 min of intraperitoneal administration of 2.5 mg of OXY. BOLD activation was detected in 72 regions out of 122, and was most prominent in areas of high μ opioid receptor density (thalamus, ventral tegmental area, substantia nigra, caudate putamen, basal amygdala, and hypothalamus), and focus on pain circuits indicated strong activation in major pain processing centers (central amygdala, solitary tract, parabrachial area, insular cortex, gigantocellularis area, ventral thalamus primary sensory cortex, and prelimbic cortex). Importantly, the OXY-induced positive BOLD was eliminated in MuKO mice in most regions, with few exceptions (some cerebellar nuclei, CA3 of the hippocampus, medial amygdala, and preoptic areas). This result indicates that most effects of OXY on positive BOLD are mediated by the μ opioid receptor (on-target effects). OXY also caused an increase in negative BOLD in WT mice in few regions (16 out of 122) and, unlike the positive BOLD response the negative BOLD was only partially eliminated in the MuKO mice (cerebellum), and in some case intensified (hippocampus). Negative BOLD analysis therefore shows activation and deactivation events in the absence of the μ receptor for some areas where receptor expression is normally extremely low or absent (off-target effects). Together, our approach permits establishing opioid-induced BOLD activation maps in awake mice. In addition, comparison of WT and MuKO mutant mice reveals both on-target and off-target activation events, and set an OXY brain signature that should, in the future, be compared to other μ opioid agonists.
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Affiliation(s)
- Kelsey Moore
- Department of Psychology, Center for Translational NeuroImaging, Northeastern University Boston, MA, USA
| | - Dan Madularu
- Brain Imaging Center, Douglas Hospital Research Institute, McGill University Montreal, QC, Canada
| | - Sade Iriah
- Department of Psychology, Center for Translational NeuroImaging, Northeastern University Boston, MA, USA
| | - Jason R Yee
- Department of Psychology, Center for Translational NeuroImaging, Northeastern University Boston, MA, USA
| | - Praveen Kulkarni
- Department of Psychology, Center for Translational NeuroImaging, Northeastern University Boston, MA, USA
| | - Emmanuel Darcq
- Brain Imaging Center, Douglas Hospital Research Institute, McGill University Montreal, QC, Canada
| | - Brigitte L Kieffer
- Brain Imaging Center, Douglas Hospital Research Institute, McGill University Montreal, QC, Canada
| | - Craig F Ferris
- Department of Psychology, Center for Translational NeuroImaging, Northeastern University Boston, MA, USA
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Lowen SB, Rohan ML, Gillis TE, Thompson BS, Wellons CBW, Andersen SL. Cocaine-conditioned odor cues without chronic exposure: Implications for the development of addiction vulnerability. NEUROIMAGE-CLINICAL 2015; 8:652-9. [PMID: 27006904 PMCID: PMC4788503 DOI: 10.1016/j.nicl.2015.06.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2014] [Revised: 05/28/2015] [Accepted: 06/19/2015] [Indexed: 11/22/2022]
Abstract
Adolescents are highly vulnerable to addiction and are four times more likely to become addicted at first exposure than at any other age. The dopamine D1 receptor, which is typically overexpressed in the normal adolescent prefrontal cortex, is involved in drug cue responses and is associated with relapse in animal models. In human drug addicts, imaging methods have detected increased activation in response to drug cues in reward- and habit-associated brain regions. These same methods can be applied more quantitatively to rodent models. Here, changes in neuronal activation in response to cocaine-conditioned cues were observed using functional magnetic resonance imaging in juvenile rats that were made to over-express either D1 receptors or green fluorescent protein by viral-mediated transduction. Reduced activation was observed in the amygdala and dopamine cell body regions in the low cue-preferring/control juvenile rats in response to cocaine cues. In contrast, increased activation was observed in the dorsal striatum, nucleus accumbens, prefrontal cortex, and dopamine cell bodies in high cue-preferring/D1 juveniles. The increase in cue salience that is mediated by increased D1 receptor density, rather than excessive cocaine experience, appears to underlie the transition from aversion to reward in cue-induced neural response and may form the basis for habit-forming vulnerability. Increased D1 receptors in prefrontal cortex increase BOLD in addiction regions. Cocaine-associated cues activated the amygdala when cocaine was preferred. Cocaine cues deactivated the amygdala in the absence of cocaine preference. Genetic engineering can be used to isolate functional responses in neural circuitry.
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Key Words
- BLA, basolateral amygdala
- BOLD, blood oxygenation level determination
- Cocaine
- Cue
- D1
- DSTR, dorsal striatum
- Development
- NAc, nucleus accumbens
- Odor
- PFC, prefrontal cortex
- ROI, region of interest
- SNc/r, substantia nigra pars compacta/reticulata
- Striatum
- VTA, ventral tegmental area
- fMRI, functional magnetic resonance imaging
- pharmacoMRI, pharmacological magnetic resonance imaging
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Affiliation(s)
- Steven B Lowen
- Brain Imaging Center, McLean Hospital, Harvard Medical School, Belmont, MA 02478, USA; Department of Psychiatry, McLean Hospital, Harvard Medical School, Belmont, MA 02478, USA
| | - Michael L Rohan
- Brain Imaging Center, McLean Hospital, Harvard Medical School, Belmont, MA 02478, USA; Department of Psychiatry, McLean Hospital, Harvard Medical School, Belmont, MA 02478, USA
| | - Timothy E Gillis
- Brain Imaging Center, McLean Hospital, Harvard Medical School, Belmont, MA 02478, USA
| | - Britta S Thompson
- Laboratory for Developmental Neuropharmacology, McLean Hospital, Harvard Medical School, Belmont, MA 02478, USA
| | - Clara B W Wellons
- Brain Imaging Center, McLean Hospital, Harvard Medical School, Belmont, MA 02478, USA
| | - Susan L Andersen
- Laboratory for Developmental Neuropharmacology, McLean Hospital, Harvard Medical School, Belmont, MA 02478, USA; Department of Psychiatry, McLean Hospital, Harvard Medical School, Belmont, MA 02478, USA
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Bourke JH, Wall MB. phMRI: methodological considerations for mitigating potential confounding factors. Front Neurosci 2015; 9:167. [PMID: 25999812 PMCID: PMC4423340 DOI: 10.3389/fnins.2015.00167] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 04/23/2015] [Indexed: 11/16/2022] Open
Abstract
Pharmacological Magnetic Resonance Imaging (phMRI) is a variant of conventional MRI that adds pharmacological manipulations in order to study the effects of drugs, or uses pharmacological probes to investigate basic or applied (e.g., clinical) neuroscience questions. Issues that may confound the interpretation of results from various types of phMRI studies are briefly discussed, and a set of methodological strategies that can mitigate these problems are described. These include strategies that can be employed at every stage of investigation, from study design to interpretation of resulting data, and additional techniques suited for use with clinical populations are also featured. Pharmacological MRI is a challenging area of research that has both significant advantages and formidable difficulties, however with due consideration and use of these strategies many of the key obstacles can be overcome.
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Affiliation(s)
- Julius H Bourke
- Centre for Psychiatry, The London School of Medicine and Dentistry, Wolfson Barts Institute for Preventive Medicine, Queen Mary University of London London, UK
| | - Matthew B Wall
- Imanova Centre for Imaging Sciences, Imperial College London, Hammersmith Hospital London, UK ; Division of Brain Sciences, Imperial College London London, UK
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Rouine J, Kelly ME, Jennings-Murphy C, Duffy P, Gorman I, Gormley S, Kerskens CM, Harkin A. Investigation of the mechanisms mediating MDMA "Ecstasy"-induced increases in cerebro-cortical perfusion determined by btASL MRI. Psychopharmacology (Berl) 2015; 232:1501-13. [PMID: 25366875 DOI: 10.1007/s00213-014-3790-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Accepted: 10/19/2014] [Indexed: 01/16/2023]
Abstract
RATIONALE Acute administration of the recreational drug of abuse 3,4-methylenedioxymethamphetamine (MDMA; Ecstasy) has previously been shown to increase cerebro-cortical perfusion as determined by bolus-tracking arterial spin labelling (btASL) MRI. OBJECTIVES The purpose of the current study was to assess the mechanisms mediating these changes following systemic administration of MDMA to rats. METHODS Pharmacological manipulation of serotonergic, dopaminergic and nitrergic transmission was carried out to determine the mechanism of action of MDMA-induced increases in cortical perfusion using btASL MRI. RESULTS Fenfluramine (10 mg/kg), like MDMA (20 mg/kg), increased cortical perfusion. Increased cortical perfusion was not obtained with the 5-HT2 receptor agonist 2,5-dimethoxy-4-iodophenyl-aminopropane hydrochloride (DOI) (1 mg/kg). Depletion of central 5-HT following systemic administration of the tryptophan hydroxylase inhibitor para-chlorophenylalanine (pCPA) produced effects similar to those observed with MDMA. Pre-treatment with the 5-HT receptor antagonist metergoline (4 mg/kg) or with the 5-HT reuptake inhibitor citalopram (30 mg/kg), however, failed to produce any effect alone or influence the response to MDMA. Pre-treatment with the dopamine D1 receptor antagonist SCH 23390 (1 mg/kg) failed to influence the changes in cortical perfusion obtained with MDMA. Treatment with the neuronal nitric oxide (NO) synthase inhibitor 7-nitroindazole (7-NI) (25 mg/kg) provoked no change in cerebral perfusion alone yet attenuated the MDMA-related increase in cortical perfusion. CONCLUSIONS Cortical 5-HT depletion is associated with increases in perfusion although this mechanism alone does not account for MDMA-related changes. A role for NO, a key regulator of cerebrovascular perfusion, is implicated in MDMA-induced increases in cortical perfusion.
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Affiliation(s)
- J Rouine
- Trinity College Institute of Neuroscience, Trinity College, Dublin, 2, Ireland
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26
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Kashiwagi Y, Rokugawa T, Yamada T, Obata A, Watabe H, Yoshioka Y, Abe K. Pharmacological MRI response to a selective dopamine transporter inhibitor, GBR12909, in awake and anesthetized rats. Synapse 2015; 69:203-12. [PMID: 25612063 DOI: 10.1002/syn.21803] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 01/06/2015] [Indexed: 12/20/2022]
Abstract
Pharmacological magnetic resonance imaging (phMRI) is a powerful tool for imaging the effects of drugs on brain activity. In preclinical phMRI studies, general anesthesia used for minimizing head movements is thought to influence the phMRI responses to drugs. In this study we investigated the phMRI responses to a selective dopamine transporter (DAT) inhibitor, GBR12909, and a dopamine (DA) releaser, d-amphetamine (AMPH), in the isoflurane anesthetized and awake rats using a relative cerebral blood volume (rCBV) method. AMPH (1 mg/kg i.p.) caused an increase in rCBV in the dopaminergic circuitry in the both anesthetized and awake rats. The striatal rCBV change was correlated with the change of the striatal DA concentration induced by AMPH in the both anesthetized and awake rats. GBR12909 (10 mg/kg i.p.) caused a positive rCBV response and showed a similar regional pattern of rCBV response to AMPH in the awake rats, and the correlation between the change of the striatal rCBV and the striatal DA concentration was observed. However, in the anesthetized rats, GBR12909 induced a widespread negative rCBV response, whereas an increase in striatal DA concentration was observed. These findings indicate that phMRI responses to activation of DA neurotransmission by GBR12909 or AMPH are overall identical in the awake state, while the phMRI response to a DAT inhibitor, GBR12909 but not to AMPH was changed by isoflurane anesthesia. For the evaluation of neuroactive drugs using phMRI, isoflurane anesthesia might be complicated the interpretation of pharmacodynamic effects of drugs in preclinical studies.
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Affiliation(s)
- Yuto Kashiwagi
- Department of Drug Metabolism and Pharmacokinetics, Research Laboratory for Development, Shionogi and Co., Ltd., Osaka, Japan; Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
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27
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Pharmacologic MRI (phMRI) as a tool to differentiate Parkinson's disease-related from age-related changes in basal ganglia function. Neurobiol Aging 2014; 36:1174-82. [PMID: 25443764 DOI: 10.1016/j.neurobiolaging.2014.10.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Revised: 08/27/2014] [Accepted: 10/12/2014] [Indexed: 12/24/2022]
Abstract
The prevalence of both parkinsonian signs and Parkinson's disease (PD) per se increases with age. Although the pathophysiology of PD has been studied extensively, less is known about the functional changes taking place in the basal ganglia circuitry with age. To specifically address this issue, 3 groups of rhesus macaques were studied: normal middle-aged animals (used as controls), middle-aged animals with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonism, and aged animals (>20 years old) with declines in motor function. All animals underwent the same behavioral and pharmacologic magnetic resonance imaging (phMRI) procedures to measure changes in basal ganglia function in response to dopaminergic drug challenges consisting of apomorphine administration followed by either a D1 (SCH23390) or a D2 (raclopride) receptor antagonist. Significant functional changes were predominantly seen in the external segment of the globus pallidus (GPe) in aged animals and in the striatum (caudate nucleus and putamen) in MPTP-lesioned animals. Despite significant differences seen in the putamen and GPe between MPTP-lesioned versus aged animals, a similar response profile to dopaminergic stimulations was found between these 2 groups in the internal segment of the GP. In contrast, the pharmacologic responses seen in the control animals were much milder compared with the other 2 groups in all the examined areas. Our phMRI findings in MPTP-lesioned parkinsonian and aged animals suggest that changes in basal ganglia function in the elderly may differ from those seen in parkinsonian patients and that phMRI could be used to distinguish PD from other age-associated functional alterations in the brain.
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28
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Choi JK, Carreras I, Aytan N, Jenkins-Sahlin E, Dedeoglu A, Jenkins BG. The effects of aging, housing and ibuprofen treatment on brain neurochemistry in a triple transgene Alzheimer's disease mouse model using magnetic resonance spectroscopy and imaging. Brain Res 2014; 1590:85-96. [PMID: 25301691 DOI: 10.1016/j.brainres.2014.09.067] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Revised: 09/09/2014] [Accepted: 09/27/2014] [Indexed: 01/18/2023]
Abstract
We investigated a triple transgene Alzheimer's disease (AD) mouse model that recapitulates many of the neurochemical, anatomic, pathologic and behavioral defects seen in human AD. We studied the mice as a function of age and brain region and investigated potential therapy with the non-steroidal anti-inflammatory drug ibuprofen. Magnetic resonance spectroscopy (MRS) showed alterations characteristic of AD (i.e. increased myo-inositol and decreased N-acetylaspartate (NAA)). Mice at 6 months of age showed an increase in myo-inositol in the hippocampus at a time when the Aβ is intracellular, but not in amygdala or cortex. Myo-inositol increased as a function of age in the amygdala, cortex and striatum while NAA decreased only in the hippocampus and cortex at 17-23 months of age. Ibuprofen protected the increase of myo-inositol at six months of age in the hippocampus, but had no effect at 17-23 months of age (a time when Aβ is extracellular). In vivo MRI and MRS showed that at 17-23 months of age there was a significant protective effect of ibuprofen on hippocampal volume and NAA loss. Together, these data show the following: the increase in myo-inositol occurs before the decrease in NAA in hippocampus but not cortex; the hippocampus shows earlier changes than does the amygdale or cortex consistent with earlier deposition of Aβ40-42 in the hippocampus and ibuprofen protects against multiple components of the AD pathology. These data also show a profound effect of housing on this particular mouse model.
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Affiliation(s)
- Ji-Kyung Choi
- Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA.
| | - Isabel Carreras
- Department of Veterans Affairs, VA Boston Healthcare System, Boston, MA 02130, USA; Department of Biochemistry, Boston University School of Medicine, Boston, MA, USA
| | - Nur Aytan
- Department of Veterans Affairs, VA Boston Healthcare System, Boston, MA 02130, USA; Neurology and Alzheimer's Disease Center, Boston University School of Medicine, Boston, MA, USA
| | - Eric Jenkins-Sahlin
- Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA
| | - Alpaslan Dedeoglu
- Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA; Department of Veterans Affairs, VA Boston Healthcare System, Boston, MA 02130, USA; Neurology and Alzheimer's Disease Center, Boston University School of Medicine, Boston, MA, USA
| | - Bruce G Jenkins
- Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA.
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29
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Viviani R, Lehmann ML, Stingl JC. Use of magnetic resonance imaging in pharmacogenomics. Br J Clin Pharmacol 2014; 77:684-94. [PMID: 23802603 PMCID: PMC3971984 DOI: 10.1111/bcp.12197] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Accepted: 06/18/2013] [Indexed: 01/11/2023] Open
Abstract
Because of the large variation in the response to psychoactive medication, many studies have attempted to uncover genetic factors that determine response. While considerable knowledge exists on the large effects of genetic polymorphisms on pharmacokinetics and plasma concentrations of drugs, effects of the concentration at the target site and pharmacodynamic effects on brain functions in disease are much less known. This article reviews the role of magnetic resonance imaging (MRI) to visualize response to medication in brain behaviour circuits in vivo in humans and assess the influence of pharmacogenetic factors. Two types of studies have been used to characterize effects of medication and genetic variation. In task-related activation studies the focus is on changes in the activity of a neural circuit associated with a specific psychological process. The second type of study investigates resting state perfusion. These studies provide an assessment of vascular changes associated with bioavailability of drugs in the brain, but may also assess changes in neural activity after binding of centrally active agents. Task-related pharmacogenetic studies of cognitive function have characterized the effects in the prefrontal cortex of genetic polymorphisms of dopamine receptors (DRD2), metabolic enzymes (COMT) and in the post-synaptic signalling cascade under the administration of dopamine agonists and antagonists. In contrast, pharmacogenetic imaging with resting state perfusion is still in its infancy. However, the quantitative nature of perfusion imaging, its non-invasive character and its repeatability might be crucial assets in visualizing the effects of medication in vivo in man during therapy.
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Affiliation(s)
- Roberto Viviani
- Department of Psychiatry and Psychotherapy III, University of Ulm, Ulm, Germany; Institute of Psychology, University of Innsbruck, Innsbruck, Austria
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30
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Kim SG, Harel N, Jin T, Kim T, Lee P, Zhao F. Cerebral blood volume MRI with intravascular superparamagnetic iron oxide nanoparticles. NMR IN BIOMEDICINE 2013; 26. [PMID: 23208650 PMCID: PMC3700592 DOI: 10.1002/nbm.2885] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The cerebral blood volume (CBV) is a crucial physiological indicator of tissue viability and vascular reactivity. Thus, noninvasive CBV mapping has been of great interest. For this, ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles, including monocrystalline iron oxide nanoparticles, can be used as long-half-life, intravascular susceptibility agents of CBV MRI measurements. Moreover, CBV-weighted functional MRI (fMRI) with USPIO nanoparticles provides enhanced sensitivity, reduced large vessel contribution and improved spatial specificity relative to conventional blood oxygenation level-dependent fMRI, and measures a single physiological parameter that is easily interpretable. We review the physiochemical and magnetic properties, and pharmacokinetics, of USPIO nanoparticles in brief. We then extensively discuss quantifications of baseline CBV, vessel size index and functional CBV change. We also provide reviews of dose-dependent sensitivity, vascular filter function, specificity, characteristics and impulse response function of CBV fMRI. Examples of CBV fMRI specificity at the laminar and columnar resolution are provided. Finally, we briefly review the application of CBV measurements to functional and pharmacological studies in animals. Overall, the use of USPIO nanoparticles can determine baseline CBV and its changes induced by functional activity and pharmacological interventions.
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Affiliation(s)
- Seong-Gi Kim
- Neuroimaging Laboratory, Department of Radiology, University of Pittsburgh, PA, USA.
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31
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Pharmacological imaging as a tool to visualise dopaminergic neurotoxicity. Neuropharmacology 2013; 84:159-69. [PMID: 23851258 DOI: 10.1016/j.neuropharm.2013.06.029] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Revised: 06/06/2013] [Accepted: 06/27/2013] [Indexed: 11/20/2022]
Abstract
Dopamine abnormalities underlie a wide variety of psychopathologies, including ADHD and schizophrenia. A new imaging technique, pharmacological magnetic resonance imaging (phMRI), is a promising non-invasive technique to visualize the dopaminergic system in the brain. In this review we explore the clinical potential of phMRI in detecting dopamine dysfunction or neurotoxicity, assess its strengths and weaknesses and identify directions for future research. Preclinically, phMRI is able to detect severe dopaminergic abnormalities quite similar to conventional techniques such as PET and SPECT. phMRI benefits from its high spatial resolution and the possibility to visualize both local and downstream effects of dopaminergic neurotransmission. In addition, it allows for repeated measurements and assessments in vulnerable populations. The major challenge is the complex interpretation of phMRI results. Future studies in patients with dopaminergic abnormalities need to confirm the currently reviewed preclinical findings to validate the technique in a clinical setting. Eventually, based on the current review we expect that phMRI can be of use in a clinical setting involving vulnerable populations (such as children and adolescents) for diagnosis and monitoring treatment efficacy. This article is part of the Special Issue Section entitled 'Neuroimaging in Neuropharmacology'.
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33
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Neurovascular coupling to D2/D3 dopamine receptor occupancy using simultaneous PET/functional MRI. Proc Natl Acad Sci U S A 2013; 110:11169-74. [PMID: 23723346 DOI: 10.1073/pnas.1220512110] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
This study employed simultaneous neuroimaging with positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) to demonstrate the relationship between changes in receptor occupancy measured by PET and changes in brain activity inferred by fMRI. By administering the D2/D3 dopamine receptor antagonist [(11)C]raclopride at varying specific activities to anesthetized nonhuman primates, we mapped associations between changes in receptor occupancy and hemodynamics [cerebral blood volume (CBV)] in the domains of space, time, and dose. Mass doses of raclopride above tracer levels caused increases in CBV and reductions in binding potential that were localized to the dopamine-rich striatum. Moreover, similar temporal profiles were observed for specific binding estimates and changes in CBV. Injection of graded raclopride mass doses revealed a monotonic coupling between neurovascular responses and receptor occupancies. The distinct CBV magnitudes between putamen and caudate at matched occupancies approximately matched literature differences in basal dopamine levels, suggesting that the relative fMRI measurements reflect basal D2/D3 dopamine receptor occupancy. These results can provide a basis for models that relate dopaminergic occupancies to hemodynamic changes in the basal ganglia. Overall, these data demonstrate the utility of simultaneous PET/fMRI for investigations of neurovascular coupling that correlate neurochemistry with hemodynamic changes in vivo for any receptor system with an available PET tracer.
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Fox GB, McGaraughty S, Luo Y. Pharmacological and functional magnetic resonance imaging techniques in CNS drug discovery. Expert Opin Drug Discov 2013; 1:211-24. [PMID: 23495843 DOI: 10.1517/17460441.1.3.211] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Functional magnetic resonance imaging (fMRI) has transformed cognitive neuroscience over the past 10 - 15 years, allowing clinical researchers unprecedented access to the functioning of the human brain under many different conditions including motor, sensory and cognitive stimulation. During the past 5 years, increasing interest has also focused on mapping pharmacologically induced changes in human brain activity produced following exposure to psychoactive agents such as amphetamine and cocaine, and is now frequently termed pharmacological MRI (phMRI). Unfortunately, preclinical fMRI and phMRI studies have not kept pace with human research, largely due to numerous technical hurdles inherent in small laboratory animal imaging, as well as the high cost of necessary equipment. However, this is now set to change with significant investment being made across academic and industry laboratories, as researchers attempt to tap into the huge potential of this noninvasive and powerful translational tool. This review introduces the principles and fundamental assumptions behind the technologies, details some important applications of fMRI and phMRI within a CNS research environment, and examines the potential future impact of the technology.
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Affiliation(s)
- Gerard B Fox
- Advanced Technology, Global Pharmaceutical Research Division, Abbott Laboratories, Abbott Park, Illinois 60064-6119, USA.
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35
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A receptor-based model for dopamine-induced fMRI signal. Neuroimage 2013; 75:46-57. [PMID: 23466936 DOI: 10.1016/j.neuroimage.2013.02.036] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Revised: 02/11/2013] [Accepted: 02/20/2013] [Indexed: 01/22/2023] Open
Abstract
This report describes a multi-receptor physiological model of the fMRI temporal response and signal magnitude evoked by drugs that elevate synaptic dopamine in basal ganglia. The model is formulated as a summation of dopamine's effects at D1-like and D2-like receptor families, which produce functional excitation and inhibition, respectively, as measured by molecular indicators like adenylate cyclase or neuroimaging techniques like fMRI. Functional effects within the model are described in terms of relative changes in receptor occupancies scaled by receptor densities and neuro-vascular coupling constants. Using literature parameters, the model reconciles many discrepant observations and interpretations of pre-clinical data. Additionally, we present data showing that amphetamine stimulation produces fMRI inhibition at low doses and a biphasic response at higher doses in the basal ganglia of non-human primates (NHP), in agreement with model predictions based upon the respective levels of evoked dopamine. Because information about dopamine release is required to inform the fMRI model, we simultaneously acquired PET (11)C-raclopride data in several studies to evaluate the relationship between raclopride displacement and assumptions about dopamine release. At high levels of dopamine release, results suggest that refinements of the model will be required to consistently describe the PET and fMRI data. Overall, the remarkable success of the model in describing a wide range of preclinical fMRI data indicate that this approach will be useful for guiding the design and analysis of basic science and clinical investigations and for interpreting the functional consequences of dopaminergic stimulation in normal subjects and in populations with dopaminergic neuroadaptations.
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36
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Lu H, Chefer S, Kurup PK, Guillem K, Vaupel DB, Ross TJ, Moore A, Yang Y, Peoples LL, Stein EA. fMRI response in the medial prefrontal cortex predicts cocaine but not sucrose self-administration history. Neuroimage 2012; 62:1857-66. [PMID: 22664568 PMCID: PMC3875563 DOI: 10.1016/j.neuroimage.2012.05.076] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Revised: 04/04/2012] [Accepted: 05/28/2012] [Indexed: 10/28/2022] Open
Abstract
Repeated cocaine exposure induces long-lasting neuroadaptations that alter subsequent responsiveness to the drug. However, systems-level investigation of these neuroplastic consequences is limited. We employed a rodent model of drug addiction to investigate neuroadaptations associated with prolonged forced abstinence after long-term cocaine self-administration (SA). Since natural rewards also activate the mesolimbic reward system in a partially overlapping fashion as cocaine, our design also included a sucrose SA group. Rats were trained to self-administer cocaine or sucrose using a fixed-ratio one, long-access schedule (6 h/day for 20 days). A third group of naïve, sedentary rats served as a negative control. After 30 days of abstinence, the reactivity of the reward system was assessed with functional magnetic resonance imaging (fMRI) following an intravenous cocaine injection challenge. A strong positive fMRI response, as measured by fractional cerebral blood volume changes relative to baseline (CBV%), was seen in the sedentary control group in such cortico-limbic regions as medial prefrontal cortex and anterior cingulate cortex. In contrast, both the cocaine and sucrose SA groups demonstrated a very similar initial negative fMRI response followed by an attenuated positive response. The magnitude of the mPFC response was significantly correlated with the total amount of reinforcer intake during the training sessions for the cocaine SA but not for the sucrose SA group. Given that the two SA groups had identical histories of operant training and handling, this region-specific group difference revealed by regression analysis may reflect the development of neuroadaptive mechanisms specifically related to the emergence of addiction-like behavior that occurs only in cocaine SA animals.
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Affiliation(s)
- Hanbing Lu
- Neuroimaging Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA
| | - Svetlana Chefer
- Neuroimaging Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA
| | - Pradeep K. Kurup
- Neuroimaging Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA
| | - Karine Guillem
- Department of Psychiatry, TRL, University of Pennsylvania, Philadelphia, PA 19104, USA
- Université de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000 Bordeaux, France
- CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000 Bordeaux, France
| | - D. Bruce Vaupel
- Neuroimaging Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA
| | - Thomas J. Ross
- Neuroimaging Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA
| | - Anna Moore
- Molecular Imaging Laboratory, MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA 02129, USA
| | - Yihong Yang
- Neuroimaging Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA
| | - Laura L. Peoples
- Department of Psychiatry, TRL, University of Pennsylvania, Philadelphia, PA 19104, USA
- Neuroscience Graduate Group, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 N 15th St, Philadelphia PA 19102, USA
| | - Elliot A. Stein
- Neuroimaging Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA
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Pharmacologic magnetic resonance imaging (phMRI): imaging drug action in the brain. Neuroimage 2012; 62:1072-85. [PMID: 22495143 DOI: 10.1016/j.neuroimage.2012.03.075] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 03/23/2012] [Indexed: 02/01/2023] Open
Abstract
The technique of functional magnetic resonance (fMRI), using various cognitive, motor and sensory stimuli has led to a revolution in the ability to map brain function. Drugs can also be used as stimuli to elicit an hemodynamic change. Stimulation with a pharmaceutical has a number of very different consequences compared to user controllable stimuli, most importantly in the time course of stimulus and response that is not, in general, controllable by the experimenter. Therefore, this type of experiment has been termed pharmacologic MRI (phMRI). The use of a drug stimulus leads to a number of interesting possibilities compared to conventional fMRI. Using receptor specific ligands one can characterize brain circuitry specific to neurotransmitter systems. The possibility exists to measure parameters reflecting neurotransmitter release and binding associated with the pharmacokinetics and/or the pharmacodynamics of drugs. There is also the ability to measure up- and down-regulation of receptors in specific disease states. phMRI can be characterized as a molecular imaging technique using the natural hemodynamic transduction related to neuro-receptor stimulus. This provides a coupling mechanism with very high sensitivity that can rival positron emission tomography (PET) in some circumstances. The large numbers of molecules available, that do not require a radio-label, means that phMRI becomes a very useful tool for performing drug discovery. Data and arguments will be presented to show that phMRI can provide information on neuro-receptor signaling and function that complements the static picture generated by PET studies of receptor numbers and occupancies.
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Shih YYI, Chiang YC, Shyu BC, Jaw FS, Duong TQ, Chang C. Endogenous opioid-dopamine neurotransmission underlie negative CBV fMRI signals. Exp Neurol 2012; 234:382-8. [PMID: 22245158 DOI: 10.1016/j.expneurol.2011.12.042] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Revised: 12/22/2011] [Accepted: 12/25/2011] [Indexed: 10/14/2022]
Abstract
Previous studies showed noxious unilateral forepaw electrical stimulation surprisingly evoked negative blood-oxygenation-level-dependent (BOLD), cerebral blood flow (CBF), and cerebral blood volume (CBV) fMRI responses in the bilateral striatum whereas the local neuronal spike and c-Fos activities increased. These negative responses are associated with vasoconstriction and appeared to override the increased hemodynamic responses that typically accompanied with increased neural activity. The current study aimed to investigate the role of μ-opioid system in modulating vasoconstriction in the striatum associated with noxious stimulation on a 4.7-Tesla MRI scanner. Specifically, we investigated: i) how morphine (a μ-opioid receptor agonist) affects the vasoconstriction in the bilateral striatum associated with noxious electrical forepaw stimulation in rats, and ii) how naloxone (an opioid receptor antagonist) and eticlopride (a dopamine D(2)/D(3) receptor antagonist) modulates the morphine effects onwards. Injection of morphine enhanced the negative striatal CBV responses to noxious stimulation. Sequential injection of naloxone in the same animals abolished the stimulus-evoked vasoconstriction. In a separate group of animals, injection of eticlopride following morphine also reduced the vasoconstriction. Our findings suggested that noxious stimulation endogenously activated opioid and dopamine receptors in the striatum and thus leading to vasoconstriction.
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Affiliation(s)
- Yen-Yu I Shih
- Department of Neurology and Biomedical Research Imaging Center, University of North Carolina, 124 Mason Farm Rd, CB#7513, Chapel Hill, NC 27599, USA.
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Chen YI, Famous K, Xu H, Choi JK, Mandeville JB, Schmidt HD, Pierce RC, Jenkins BG. Cocaine self-administration leads to alterations in temporal responses to cocaine challenge in limbic and motor circuitry. Eur J Neurosci 2011; 34:800-15. [PMID: 21896062 PMCID: PMC3172610 DOI: 10.1111/j.1460-9568.2011.07806.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Chronic use of cocaine is associated with lasting alterations in brain metabolism, circuitry, and receptor properties. We used neuroimaging with pharmacological magnetic resonance imaging to assess alterations in response to cocaine (0.5 mg/kg) in animals trained to self-administer cocaine on a fixed-ratio 5 schedule of reinforcement, as well as saline-yoked controls, after 28 days of cocaine abstinence. We fitted the cerebral blood volume (CBV) curves for full-width half-maximum (FWHM) as well as peak CBV response. There were significant increases in the FWHM of the response curves in the cocaine self-administering (SA) animals as compared with saline-yoked controls in the medial prefrontal cortex (mPFC) and the caudate/putamen (CPu), and increases in peak CBV in the M1 motor cortex, CPu, and pedunculopontine tegmental nucleus. Functional connectivity analysis showed increased correlations in the cocaine SA rats upon acute cocaine challenge, especially in the S1, mPFC, and thalamus. As D3 receptor expression is postulated to increase following chronic cocaine administration, we also examined the response to 0.2 mg/kg of the D3-preferring agonist 7-hydroxy-N,N-di-n-propyl-2-aminotetralin (7-OHDPAT). Cocaine SA animals showed a decreased overall CBV response to this drug, except in the globus pallidus. The hypothalamus showed a negative CBV change in response to cocaine challenge, similar to that noted with the D3 agonist, and showed a smaller response in the cocaine SA animals than in the controls. Given the good coupling of cerebral hemodynamics with dopamine dynamics previously observed with pharmacological magnetic resonance imaging, these data suggest that increased persistence of dopamine in the prefrontal cortex may be responsible for some of the behavioral alterations observed subsequent to chronic cocaine use.
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Affiliation(s)
- Y Iris Chen
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA.
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fMRI of cocaine self-administration in macaques reveals functional inhibition of basal ganglia. Neuropsychopharmacology 2011; 36:1187-98. [PMID: 21307843 PMCID: PMC3079280 DOI: 10.1038/npp.2011.1] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Disparities in cocaine-induced neurochemical and metabolic responses between human beings and rodents motivate the use of non-human primates (NHP) to model consequences of repeated cocaine exposure in human subjects. To characterize the functional response to cocaine infusion in NHP brain, we employed contrast-enhanced fMRI during both non-contingent injection of drug and self-administration of cocaine in the magnet. Cocaine robustly decreased cerebral blood volume (CBV) throughout basal ganglia and motor/pre-motor cortex and produced subtle functional inhibition of prefrontal cortex. No brain regions exhibited significant elevation of CBV in response to cocaine challenge. Theses effects in NHP brain are opposite in sign to the cocaine-induced fMRI response in rats, but consistent with previous measurements in NHP based on glucose metabolism. Because the striatal ratio of D2 to D1 receptors is larger in human beings and NHP than rats, we hypothesize that the inhibitory effects of D2 receptor binding dominate the functional response in primates, whereas excitatory D1 receptor stimulation predominates in the rat. If the NHP accurately models the human response to cocaine, downregulation of D2 receptors in human cocaine-abusing populations can be expected to blunt cocaine-induced functional responses, contributing to the weak and variable fMRI responses reported in human basal ganglia following cocaine infusion.
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Kapogiannis D, Mooshagian E, Campion P, Grafman J, Zimmermann TJ, Ladt KC, Wassermann EM. Reward processing abnormalities in Parkinson's disease. Mov Disord 2011; 26:1451-7. [PMID: 21538525 DOI: 10.1002/mds.23701] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Revised: 01/06/2011] [Accepted: 02/07/2011] [Indexed: 01/12/2023] Open
Abstract
The primary motor cortex is important for motor learning and response selection, functions that require information on the expected and actual outcomes of behavior. Therefore, it should receive signals related to reward. Pathways from reward centers to motor cortex exist in primates. Previously, we showed that gamma aminobutyric acid-A-mediated inhibition in the motor cortex, measured by paired transcranial magnetic stimulation, changes with expectation and uncertainty of money rewards generated by a slot machine simulation. We examined the role of dopamine in this phenomenon by testing 13 mildly affected patients with Parkinson's disease, off and on dopaminergic medications, and 13 healthy, age-matched controls. Consistent with a dopaminergic mechanism, reward expectation or predictability modulated the response to paired transcranial magnetic stimulation in controls, but not in unmedicated patients. A single dose of pramipexole restored this effect of reward, mainly by increasing the paired transcranial magnetic stimulation response amplitude during low expectation. Levodopa produced no such effect. Both pramipexole and levodopa increased risk-taking behavior on the Iowa Gambling Task. However, pramipexole increased risk-taking behavior more in patients showing lower paired transcranial magnetic stimulation response amplitude during low expectation. These results provide evidence that modulation of motor cortex inhibition by reward is mediated by dopamine signaling and that the physiological state of the motor cortex changes with risk-taking tendency in patients on pramipexole. The cortical response to reward expectation may represent an endophenotype for risk-taking behavior in patients on agonist treatment.
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Affiliation(s)
- Dimitrios Kapogiannis
- Behavioral Neurology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
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Sekar S, Verhoye M, Van Audekerke J, Vanhoutte G, Lowe AS, Blamire AM, Steckler T, Van der Linden A, Shoaib M. Neuroadaptive responses to citalopram in rats using pharmacological magnetic resonance imaging. Psychopharmacology (Berl) 2011; 213:521-31. [PMID: 21103865 DOI: 10.1007/s00213-010-2084-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2010] [Accepted: 10/30/2010] [Indexed: 11/30/2022]
Abstract
RATIONALE The majority of psychoactive compounds, including antidepressants in clinical practice, were discovered largely by serendipity. The underlying neuropharmacological mechanisms of action of these compounds leading to resolution of depressive symptomatology are targets of the current research. Pharmacological magnetic resonance imaging (phMRI), a rapidly developing advancement of blood oxygenation level dependent (BOLD) contrast offers the potential to localize the regional sites of action in the CNS. OBJECTIVE Acute and chronic effects of the clinically effective selective serotonin reuptake inhibitor (SSRI) citalopram were examined for changes in BOLD contrast using phMRI in rats. To pharmacologically characterize the specific involvement of the 5-HT(1A) receptors, citalopram was co-administered with a highly selective 5-HT(1A) receptor antagonist WAY100635. RESULTS Acute citalopram treatment (10 and 20 mg/kg i.p.) produced a widespread and dose-dependent activation throughout the whole brain. Following 14 days of chronic daily administration of citalopram (20 mg/kg i.p.), localized effects were observed; regions integral in the therapeutic antidepressant effects included the hypothalamus, hippocampus, and cortical regions, suggesting desensitization of serotonergic receptors in the midbrain contributing to elevated levels of 5-HT. Co-administration with WAY100635 (0.3 mg/kg s.c.) increased BOLD activation in the frontal cortex and decreased BOLD contrast in the hypothalamus, hippocampus, and hindbrain structures. CONCLUSION The present findings highlight the adaptive nature of responses to citalopram which exhibits regional and pharmacological specificity. These findings translate well to the clinical findings and suggest that this approach may offer the opportunity to develop more efficacious antidepressants with a faster clinical response.
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Affiliation(s)
- Sakthivel Sekar
- Psychobiology Research Group, Institute of Neuroscience, Newcastle upon Tyne, UK
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Pharmacological MRI approaches to understanding mechanisms of drug action. Curr Top Behav Neurosci 2011; 11:365-88. [PMID: 22057623 DOI: 10.1007/7854_2011_177] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Functional neuroimaging is a novel technique for the study of drug action in the brain. The emerging role of this method is intimately tied to the unique challenges to advancing drug development for neuropsychiatric disorders. This chapter first presents a brief overview of the important treatment needs that remain to be met, which serve as clinical targets for drug development. Important factors that hinder progress in drug development, which arise from clinical, scientific and economic issues, are acknowledged. This sets the stage for the unique advantages of functional neuroimaging modalities such as functional MRI (fMRI) as a biomarker and drug development tool, in both clinical and preclinical phases. The physiological basis of the fMRI signal is briefly outlined, and aspects of neural signaling related to this signal change, with emphasis on implications for pharmacology studies. The utility of fMRI for evaluating the full anatomic extent of central neurotransmitter systems in a dynamic manner is then described. This is a critical advantage, and particularly important for studies of how systems such as the monoamines modulate distributed neural networks during cognitive processes in both health and illness, and how these actions are modified with pharmacological intervention. Central catecholamine systems are seen as paradigmatic targets amenable to pharmacologic fMRI. fMRI is observed to occupy a unique position in the armamentarium of methods available to the pharmacologist and the drug development process, and poised to play an expanding role in basic and clinical neuroscience.
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Abstract
Over the past several decades, the relative contribution of both environmental and genetic influences in the development of aggression and violence has been explored extensively. Only fairly recently, however, has it become increasingly evident that early perinatal life events may substantially increase the vulnerability toward the development of violent and aggressive behaviors in offspring across the lifespan. Early life risk factors, such as pregnancy and birth complications and intrauterine exposure to environmental toxins, appear to have a profound and enduring impact on the neuroregulatory systems mediating violence and aggression, yet the emergence of later adverse behavioral outcomes appears to be both complex and multidimensional. The present chapter reviews available experimental and clinical findings to provide a framework on perinatal risk factors that are associated with altered developmental trajectories leading to violence and aggression, and also highlights the genetic contributions in the expression of these behaviors.
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Choi JK, Mandeville JB, Chen YI, Grundt P, Sarkar SK, Newman AH, Jenkins BG. Imaging brain regional and cortical laminar effects of selective D3 agonists and antagonists. Psychopharmacology (Berl) 2010; 212:59-72. [PMID: 20628733 PMCID: PMC3822611 DOI: 10.1007/s00213-010-1924-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Accepted: 06/15/2010] [Indexed: 02/04/2023]
Abstract
RATIONALE Dopamine D3 receptors (D3R) may be important therapeutic targets for both drug abuse and dyskinesias in Parkinson's disease; however, little is known about their functional circuitry. OBJECTIVES We wished to determine if D3R antagonists SB-277011 and PG-01037 and D3R-preferring agonist 7-OH-DPAT are D3R selective in vivo. We further wished to characterize the response to D3R drugs using whole brain imaging to identify novel D3R circuitry. METHODS We investigated D3R circuitry in rats using pharmacologic MRI and challenge with selective D3R antagonists and agonist at various doses to examine regional changes in cerebral blood volume (CBV). We compared regional activation patterns with D2R/D3R agonists, as well as with prior studies of mRNA expression and autoradiography. RESULTS D3R antagonists induced positive CBV changes and D3R agonist negative CBV changes in brain regions including nucleus accumbens, infralimbic cortex, thalamus, interpeduncular region, hypothalamus, and hippocampus (strongest in subiculum). All D3R-preferring drugs showed markedly greater responses in nucleus accumbens than in caudate/putamen consistent with D3R selectivity and contrary to what was observed with D2R agonists. At high doses of D3R agonist, functional changes were differentiated across cortical laminae, with layer V-VI yielding positive CBV changes and layer IV yielding negative CBV changes. These results are not inconsistent with differential D1R and D3R innervation in these layers respectively showed previously using post-mortem techniques. CONCLUSIONS MRI provides a new tool for testing the in vivo selectivity of novel D3R dopaminergic ligands where radiolabels may not be available. Further, the functional D3R circuitry strongly involves hypothalamus and subiculum as well as the limbic striatum.
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Affiliation(s)
- Ji-Kyung Choi
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, 02129, USA
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Chen YI, Choi JK, Xu H, Ren J, Andersen SL, Jenkins BG. Pharmacologic neuroimaging of the ontogeny of dopamine receptor function. Dev Neurosci 2010; 32:125-38. [PMID: 20523024 DOI: 10.1159/000286215] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2009] [Accepted: 02/09/2010] [Indexed: 01/23/2023] Open
Abstract
Characterization of the ontogeny of the cerebral dopaminergic system is crucial for gaining a greater understanding of normal brain development and its alterations in response to drugs of abuse or conditions such as attention-deficit hyperactivity disorder. Pharmacological MRI (phMRI) was used to determine the response to dopamine transporter (DAT) blockers cocaine and methylphenidate (MPH), the dopamine releaser D-amphetamine (AMPH), the selective D1 agonist dihydrexidine, and the D2/D3 agonist quinpirole in young (<30 days old) and adult (>60 days old) rats. In adult rats, cocaine (0.5 mg/kg i.v.) or MPH (2 mg/kg) induced primarily positive cerebral blood volume (rCBV) changes in the dopaminergic circuitry, but negative rCBV changes in the young animals. Microdialysis measurements in the striatum showed that young rats have a smaller increase in extracellular dopamine in response to cocaine than adults. The young rats showed little rCBV response to the selective D1 agonist dihydrexidine in contrast to robust rCBV increases observed in the adults, whereas there was a similar negative rCBV response in the young and adult rats to the D2 agonist quinpirole. We also performed a meta-analysis of literature data on the development of D1 and D2 receptors and the DAT. These data suggest a predominance of D2-like over D1-like function between 20 and 30 days of age. These combined results suggested that the dopamine D1 receptor is functionally inhibited at young age.
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Affiliation(s)
- Y Iris Chen
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA.
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Maina FK, Mathews TA. A functional fast scan cyclic voltammetry assay to characterize dopamine D2 and D3 autoreceptors in the mouse striatum. ACS Chem Neurosci 2010; 1:450-462. [PMID: 20567609 DOI: 10.1021/cn100003u] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Dopamine D2 and D3 autoreceptors are located on pre-synaptic terminals and are known to control the release and synthesis of dopamine. Dopamine D3 receptors have a fairly restricted pattern of expression in the mammalian brain. Their localization in the nucleus accumbens core and shell is of particular interest because of their association with the rewarding properties of drugs of abuse. Using background subtracted fast scan cyclic voltammetry, we investigated the effects of dopamine D2 and D3 agonists on electrically stimulated dopamine release and uptake rates in the mouse caudate-putamen and nucleus accumbens core and shell. The dopamine D2 agonists (-)-quinpirole hydrochloride and 5,6,7,8-Tetrahydro-6-(2-propen-1-yl)-4H-thiazolo[4,5-d]azepin-2-amine dihydrochloride (B-HT 920) had the same dopamine release inhibition effects on caudate-putamen and nucleus accumbens (core and shell) based on their EC(50) and efficacies. This suggests that the dopamine D2 autoreceptor functionality is comparable in all three striatal regions investigated. The dopamine D3 agonists (4aR,10bR)-3,4a,4,10b-Tetrahydro-4-propyl-2H,5H-[1]benzopyrano-[4,3-b]-1,4-oxazin-9-ol hydrochloride ((+)-PD 128907) and (+/-)-7-Hydroxy-2-dipropylaminotetralin hydrobromide (7-OH-DPAT) had a significantly greater effect on dopamine release inhibition in the nucleus accumbens shell than in caudate-putamen. This study confirms that, the dopamine D3 autoreceptor functionality is greater in the nucleus accumbens shell followed by the nucleus accumbens core, with the caudate-putamen having the least. Neither dopamine D2 nor D3 agonists affected the uptake rates in nucleus accumbens but concentrations greater than 0.3 muM lowered the uptake rate in caudate-putamen. To validate our method of evaluating dopamine D2 and D3 autoreceptors, sulpiride (D2 antagonist) and nafadotride (D3 antagonist) were used to reverse the effects of the dopamine agonists to approximately 100% of the pre-agonist dopamine release concentration. Finally, these results demonstrate a functional voltammetric assay that characterizes dopamine D2-like agonist as either D2- or D3-preferring agonists by taking advantage of the unique receptor density within the striatum.
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Affiliation(s)
- Francis K. Maina
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202
| | - Tiffany A. Mathews
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202
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Choi JK, Dedeoglu A, Jenkins BG. Longitudinal monitoring of motor neuron circuitry in FALS rats using in-vivo phMRI. Neuroreport 2010; 21:157-62. [PMID: 20118741 PMCID: PMC2848450 DOI: 10.1097/wnr.0b013e328330eb9e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) presents challenges for diagnosis and objective monitoring of disease progression. We show, using pharmacologic MRI, that alterations in motor circuitry can be characterized using a passive stimulus in a rat model of familial ALS as a function of symptom progression. Presymptomatic familial ALS rats had a pattern of activation to amphetamine that was statistically indistinguishable from the wild-type controls. In contrast, symptomatic rats showed significantly decreased response in sensorimotor cortex and increased response in M2 motor cortex, caudate/putamen, and thalamus. These results are similar to findings in humans of altered response to motor tasks in ALS. It may be plausible to use a passive amphetamine challenge as a biomarker to assess progression of the disease and efficacy of potential treatments.
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Affiliation(s)
- Ji-Kyung Choi
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA
| | - Alpaslan Dedeoglu
- Department of Veterans Affairs, VA Medical Center, Jamaica Plain, MA
- Department of Biochemistry, Boston University School of Medicine, Boston, MA
- Department of Neurology, Boston University School of Medicine, Boston, MA
| | - Bruce G. Jenkins
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA
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Mueggler T, Baltes C, Rudin M. Molecular neuroimaging in rodents: assessing receptor expression and function. Eur J Neurosci 2009; 30:1860-9. [DOI: 10.1111/j.1460-9568.2009.06987.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Ren J, Xu H, Choi JK, Jenkins BG, Chen YI. Dopaminergic response to graded dopamine concentration elicited by four amphetamine doses. Synapse 2009; 63:764-72. [PMID: 19484725 DOI: 10.1002/syn.20659] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
UNLABELLED We studied the metabolic responses to different DA concentrations elicited by four doses of D-amphetamine (AMPH, 0, 0.25, 0.5, 1.0, or 3.0 mg/kg). We compared the degree of DA release (via microdialysis) with striatal cAMP activity and whole brain maps of cerebral blood volume (rCBV) changes (via pharmacological MRI, phMRI). RESULTS AMPH increased DA release in the caudate/putamen (CPu) and cAMP activity in the CPu, nucleus accumbens (NAc), and medial prefrontal cortex (mPFC) in a linear dose-dependent manner (P < 0.0001). The cAMP data suggest that, postsynaptically, signal transduction induced by D1 receptor is stronger than that of D2 receptor at the higher doses (1-3 mg/kg). phMRI showed that, while higher doses of AMPH (3 mg/kg (n = 7) and 1 mg/kg (n = 6)) induced significant rCBV increases in the CPu and NAc, the degree of rCBV increase was much smaller with AMPH of 0.5 mg/kg (n = 6). In contrast, AMPH of 0.25 mg/kg (n = 8) induced significant rCBV decreases in the anteromedial CPu and NAc. The sign switch of rCBV in response to AMPH from low to high doses likely reflects the switching in the balance of D2/D3 stimulation vs. D1/D5 stimulation. In conclusion, degree of postsynaptic signal transduction is linearly correlated to the extracellular DA concentration. However, the presynaptic binding may dominate the overall DA innervation at the lower range of DA concentration.
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Affiliation(s)
- Jiaqian Ren
- Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, USA
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