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Hudson KE, Grau JW. Ionic Plasticity: Common Mechanistic Underpinnings of Pathology in Spinal Cord Injury and the Brain. Cells 2022; 11:2910. [PMID: 36139484 PMCID: PMC9496934 DOI: 10.3390/cells11182910] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 09/12/2022] [Accepted: 09/14/2022] [Indexed: 11/16/2022] Open
Abstract
The neurotransmitter GABA is normally characterized as having an inhibitory effect on neural activity in the adult central nervous system (CNS), which quells over-excitation and limits neural plasticity. Spinal cord injury (SCI) can bring about a modification that weakens the inhibitory effect of GABA in the central gray caudal to injury. This change is linked to the downregulation of the potassium/chloride cotransporter (KCC2) and the consequent rise in intracellular Cl- in the postsynaptic neuron. As the intracellular concentration increases, the inward flow of Cl- through an ionotropic GABA-A receptor is reduced, which decreases its hyperpolarizing (inhibitory) effect, a modulatory effect known as ionic plasticity. The loss of GABA-dependent inhibition enables a state of over-excitation within the spinal cord that fosters aberrant motor activity (spasticity) and chronic pain. A downregulation of KCC2 also contributes to the development of a number of brain-dependent pathologies linked to states of neural over-excitation, including epilepsy, addiction, and developmental disorders, along with other diseases such as hypertension, asthma, and irritable bowel syndrome. Pharmacological treatments that target ionic plasticity have been shown to bring therapeutic benefits.
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Affiliation(s)
- Kelsey E. Hudson
- Neuroscience, Texas A&M University, College Station, TX 77843, USA
| | - James W. Grau
- Psychological & Brain Sciences, Texas A&M University, College Station, TX 77843, USA
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2
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Yamazaki M, Arai T, Yarimizu J, Matsumoto M. 5-HT5A Receptor Antagonist ASP5736 Ameliorates Several Abnormal Behaviors in an Fmr1-Targeted Transgenic Male Rat Model of Fragile X Syndrome. Int J Neuropsychopharmacol 2022; 25:786-793. [PMID: 35882205 PMCID: PMC9515134 DOI: 10.1093/ijnp/pyac041] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 06/24/2022] [Accepted: 07/23/2022] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Fragile X syndrome (FXS) is a genetic condition that causes a range of developmental problems, including intellectual disability, aggressive behavior, anxiety, abnormal sensory processing, and cognitive impairment. Despite intensive preclinical research in Fmr1-targeted transgenic mice, an effective treatment for FXS has yet to be developed. We previously demonstrated that ASP5736, a 5-Hydroxytryptamine (serotonin) receptor 5A receptor antagonist, ameliorated scopolamine-induced working memory deficits in mice, reference memory impairment in aged rats, and methamphetamine-induced positive symptoms and phencyclidine-induced cognitive impairment in animal models of schizophrenia. We hypothesized that ASP5736 may be effective for ameliorating similar behavior deficits in male Fmr1-targeted transgenic rats as a preclinical model of FXS. METHODS We evaluated the effect of acute oral administration of ASP5736 on the abnormal behavior of hyperactivity (0.01, 0.1 mg/kg), prepulse inhibition (0.01, 0.03, 0.1 mg/kg), and the novel object recognition task (0.1 mg/kg) in Frmr1-knockout (KO) rats. RESULTS Fmr1-KO rats showed body weight gain, hyperactivity, abnormal sensory motor gating, and cognitive impairment. ASP5736 (0.1 mg/kg) reversed the hyperactivity and ameliorated the sensory motor gating deficits (0.03-0.1 mg/kg). ASP5736 (0.01 mg/kg) also improved cognitive impairment. CONCLUSIONS ASP5736 is a potential drug candidate for FXS. Further studies are needed to confirm its clinical efficacy.
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Affiliation(s)
- Mayako Yamazaki
- Correspondence: Mayako Yamazaki, PhD, Research Fellow, Department of Neuroscience, Drug Discovery Research, Astellas Pharma Inc., 21 Miyukigaoka, Tsukuba-shi, Ibaraki, 305-8585, Japan ()
| | - Takatomo Arai
- Department of Neuroscience, Drug Discovery Research, Astellas Pharma Inc., Tsukuba-shi, Ibaraki, Japan
| | - Junko Yarimizu
- Department of Neuroscience, Drug Discovery Research, Astellas Pharma Inc., Tsukuba-shi, Ibaraki, Japan
| | - Mitsuyuki Matsumoto
- Department of Neuroscience, Drug Discovery Research, Astellas Pharma Inc., Tsukuba-shi, Ibaraki, Japan,Neuroscience, La Jolla Laboratory, Astellas Research Institute of America LLC, San Diego, CA, USA
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Yamazaki M, Yamamoto N, Yarimizu J, Okabe M, Moriyama A, Furutani M, Marcus MM, Svensson TH, Harada K. Functional mechanism of ASP5736, a selective serotonin 5-HT 5A receptor antagonist with potential utility for the treatment of cognitive dysfunction in schizophrenia. Eur Neuropsychopharmacol 2018; 28:620-629. [PMID: 29571967 DOI: 10.1016/j.euroneuro.2018.03.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 02/17/2018] [Accepted: 03/02/2018] [Indexed: 10/17/2022]
Abstract
The 5-HT5A receptor is arguably the least understood 5-HT receptor. Despite widespread expression in human and rodent brains it lacks specific ligands. Our previous results suggest that 5-HT5A receptor antagonists may be effective against cognitive impairment in schizophrenia. In this study, using behavioral, immunohistochemical, electrophysiological and microdialysis techniques, we examined the mechanism by which ASP5736, a novel and selective 5-HT5A receptor antagonist, exerts a positive effect in animal models of cognitive impairment. We first confirmed the effect of ASP5736 on cognitive deficits in rats treated subchronically with phencyclidine hydrochloride (PCP) using an attentional set shifting task. Subsequently, we identified 5-HT5A receptors in dopaminergic (DAergic) neurons and parvalbumin (PV)-positive interneurons in the ventral tegmental area (VTA) and in PV-positive interneurons in the medial prefrontal cortex (mPFC). Burst firing of the DAergic cells in the parabrachial pigmental nucleus (PBP) in the VTA, which predominantly project to the mPFC, was significantly enhanced by treatment with ASP5736. In contrast, ASP5736 exerted no significant effect on either the firing rate or burst firing in the DA cells in the paranigral nucleus (PN), that project to the nucleus accumbens (N. Acc.). ASP5736 increased the release of DA and gamma-aminobutyric acid (GABA) in the mPFC of subchronically PCP-treated rats. These results support our hypothesis that ASP5736 might block the inhibitory 5-HT5A receptors on DAergic neurons in the VTA that project to the mPFC, and interneurons in the mPFC, and thereby improve cognitive impairment by preferentially enhancing DAergic and GABAergic neurons in the mPFC.
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Affiliation(s)
- Mayako Yamazaki
- Department of Neuroscience, Drug Discovery Research, Astellas Pharma Inc., 21 Miyukigaoka, Tsukuba-shi, Ibaraki 305-8585, Japan.
| | - Noriyuki Yamamoto
- Department of Neuroscience, Drug Discovery Research, Astellas Pharma Inc., 21 Miyukigaoka, Tsukuba-shi, Ibaraki 305-8585, Japan
| | - Junko Yarimizu
- Department of Neuroscience, Drug Discovery Research, Astellas Pharma Inc., 21 Miyukigaoka, Tsukuba-shi, Ibaraki 305-8585, Japan
| | - Mayuko Okabe
- Department of Neuroscience, Drug Discovery Research, Astellas Pharma Inc., 21 Miyukigaoka, Tsukuba-shi, Ibaraki 305-8585, Japan
| | - Ai Moriyama
- Analysis & Pharmacokinetics Research, Drug Discovery Research, Astellas Pharma Inc., 21 Miyukigaoka, Tsukuba-shi, Ibaraki 305-8585, Japan
| | - Masako Furutani
- Analysis & Pharmacokinetics Research, Drug Discovery Research, Astellas Pharma Inc., 21 Miyukigaoka, Tsukuba-shi, Ibaraki 305-8585, Japan
| | - Monica M Marcus
- Department of Physiology and Pharmacology, Section of Neuropsychopharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Torgny H Svensson
- Department of Physiology and Pharmacology, Section of Neuropsychopharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Katsuya Harada
- Department of Neuroscience, Drug Discovery Research, Astellas Pharma Inc., 21 Miyukigaoka, Tsukuba-shi, Ibaraki 305-8585, Japan
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Fujita M, Ide S, Ikeda K. Opioid and nondopamine reward circuitry and state-dependent mechanisms. Ann N Y Acad Sci 2018. [PMID: 29512887 DOI: 10.1111/nyas.13605] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
A common notion is that essentially all addictive drugs, including opioids, activate dopaminergic pathways in the brain reward system, and the inappropriate use of such drugs induces drug dependence. However, an opioid reward response is reportedly still observed in several models of dopamine depletion, including in animals that are treated with dopamine blockers, animals that are subjected to dopaminergic neuron lesions, and dopamine-deficient mice. The intracranial self-stimulation response is enhanced by stimulants but reduced by morphine. These findings suggest that dopaminergic neurotransmission may not always be required for opioid reward responses. Previous findings also indicate the possibility that dopamine-independent opioid reward may be observed in opioid-naive states but not in opioid-dependent states. Therefore, a history of opioid use should be considered when evaluating the dopamine dependency of opioid reward.
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Affiliation(s)
- Masayo Fujita
- Addictive Substance Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Soichiro Ide
- Addictive Substance Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Kazutaka Ikeda
- Addictive Substance Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
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Separate and Combined Effects of Naltrexone and Extended-Release Alprazolam on the Reinforcing, Subject-Rated, and Cardiovascular Effects of Methamphetamine. J Clin Psychopharmacol 2016; 36:213-21. [PMID: 27043121 PMCID: PMC4837068 DOI: 10.1097/jcp.0000000000000488] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Opioid antagonists (eg, naltrexone) and positive modulators of γ-aminobutyric acid type A receptors (eg, alprazolam) each modestly attenuate the abuse-related effects of stimulants. A previous study demonstrated that acute pretreatment with the combination of naltrexone and alprazolam attenuated a greater number of the subject-rated effects of D-amphetamine than the constituent drugs alone. This study tested the hypothesis that maintenance on the combination of naltrexone and alprazolam XR would attenuate the reinforcing and "positive" subject-rated effects of methamphetamine to a greater extent than the constituent drugs alone.Eight non-treatment-seeking, stimulant-using individuals completed a placebo-controlled, crossover, double-blind inpatient protocol. Participants were maintained on naltrexone (0 and 50 mg), alprazolam XR (0 and 1 mg), and the combination of naltrexone and alprazolam XR (50 mg and 1 mg, respectively) for 6 to 7 days. Under each maintenance condition, participants sampled intranasal doses of methamphetamine (0, 10, and 30 mg), and were then offered the opportunity to work for the sampled dose on a modified progressive-ratio procedure. Subject-rated drug effect questionnaires, psychomotor, and physiology assessments were collected.Intranasal methamphetamine functioned as a reinforcer and produced prototypical stimulant-like "positive" subject-rated and physiological effects. Maintenance on naltrexone significantly decreased the reinforcing, but not subject-rated drug effects of 10-mg methamphetamine. Alprazolam XR and the combination of naltrexone and alprazolam XR did not impact methamphetamine self-administration or subject-rated drug effects. The results support the continued evaluation of naltrexone for methamphetamine dependence, as well as the identification of other drugs that enhance its ability to reduce drug-taking behavior.
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Taylor AMW, Castonguay A, Ghogha A, Vayssiere P, Pradhan AAA, Xue L, Mehrabani S, Wu J, Levitt P, Olmstead MC, De Koninck Y, Evans CJ, Cahill CM. Neuroimmune Regulation of GABAergic Neurons Within the Ventral Tegmental Area During Withdrawal from Chronic Morphine. Neuropsychopharmacology 2016; 41:949-59. [PMID: 26202104 PMCID: PMC4748420 DOI: 10.1038/npp.2015.221] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 07/10/2015] [Accepted: 07/11/2015] [Indexed: 12/13/2022]
Abstract
Opioid dependence is accompanied by neuroplastic changes in reward circuitry leading to a negative affective state contributing to addictive behaviors and risk of relapse. The current study presents a neuroimmune mechanism through which chronic opioids disrupt the ventral tegmental area (VTA) dopaminergic circuitry that contributes to impaired reward behavior. Opioid dependence was induced in rodents by treatment with escalating doses of morphine. Microglial activation was observed in the VTA following spontaneous withdrawal from chronic morphine treatment. Opioid-induced microglial activation resulted in an increase in brain-derived neurotrophic factor (BDNF) expression and a reduction in the expression and function of the K(+)Cl(-) co-transporter KCC2 within VTA GABAergic neurons. Inhibition of microglial activation or interfering with BDNF signaling prevented the loss of Cl(-) extrusion capacity and restored the rewarding effects of cocaine in opioid-dependent animals. Consistent with a microglial-derived BDNF-induced disruption of reward, intra-VTA injection of BDNF or a KCC2 inhibitor resulted in a loss of cocaine-induced place preference in opioid-naïve animals. The loss of the extracellular Cl(-) gradient undermines GABAA-mediated inhibition, and represents a mechanism by which chronic opioid treatments can result in blunted reward circuitry. This study directly implicates microglial-derived BDNF as a negative regulator of reward in opioid-dependent states, identifying new therapeutic targets for opiate addictive behaviors.
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Affiliation(s)
- Anna M W Taylor
- Department of Anesthesiology and Perioperative Care, University of California, Irvine, CA, USA
- Hatos Center for Neuropharmacology, Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, CA, USA
| | - Annie Castonguay
- Institut Universitaire en Santé Mentale de Québec, Québec, QC, Canada
- Department of Psychiatry and Neuroscience, Université Laval, Québec, QC, Canada
| | - Atefeh Ghogha
- Hatos Center for Neuropharmacology, Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, CA, USA
| | - Pia Vayssiere
- Hatos Center for Neuropharmacology, Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, CA, USA
| | - Amynah A A Pradhan
- Hatos Center for Neuropharmacology, Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, CA, USA
| | - Lihua Xue
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada
| | - Sadaf Mehrabani
- Hatos Center for Neuropharmacology, Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, CA, USA
| | - Juli Wu
- Children's Hospital Los Angeles and the Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
| | - Pat Levitt
- Children's Hospital Los Angeles and the Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
| | - Mary C Olmstead
- Department of Psychology, Queen's University, Kingston, ON, Canada
| | - Yves De Koninck
- Institut Universitaire en Santé Mentale de Québec, Québec, QC, Canada
- Department of Psychiatry and Neuroscience, Université Laval, Québec, QC, Canada
| | - Christopher J Evans
- Hatos Center for Neuropharmacology, Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, CA, USA
| | - Catherine M Cahill
- Department of Anesthesiology and Perioperative Care, University of California, Irvine, CA, USA
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada
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Blacktop JM, Vranjkovic O, Mayer M, Van Hoof M, Baker DA, Mantsch JR. Antagonism of GABA-B but not GABA-A receptors in the VTA prevents stress- and intra-VTA CRF-induced reinstatement of extinguished cocaine seeking in rats. Neuropharmacology 2015; 102:197-206. [PMID: 26596556 DOI: 10.1016/j.neuropharm.2015.11.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 10/23/2015] [Accepted: 11/12/2015] [Indexed: 12/25/2022]
Abstract
Stress-induced reinstatement of cocaine seeking requires corticotropin releasing factor (CRF) actions in the ventral tegmental area (VTA). However the mechanisms through which CRF regulates VTA function to promote cocaine use are not fully understood. Here we examined the role of GABAergic neurotransmission in the VTA mediated by GABA-A or GABA-B receptors in the reinstatement of extinguished cocaine seeking by a stressor, uncontrollable intermittent footshock, or bilateral intra-VTA administration of CRF. Rats underwent repeated daily cocaine self-administration (1.0 mg/kg/ing; 14 × 6 h/day) and extinction and were tested for reinstatement in response to footshock (0.5 mA, 0.5" duration, average every 40 s; range 10-70 s) or intra-VTA CRF delivery (500 ng/side) following intra-VTA pretreatment with the GABA-A antagonist, bicuculline, the GABA-B antagonist, 2-hydroxysaclofen or vehicle. Intra-VTA bicuculline (1, 10 or 20 ng/side) failed to block footshock- or CRF-induced cocaine seeking at either dose tested. By contrast, 2-hydroxysaclofen (0.2 or 2 μg/side) prevented reinstatement by both footshock and intra-VTA CRF at a concentration that failed to attenuate food-reinforced lever pressing (45 mg sucrose-sweetened pellets; FR4 schedule) in a separate group of rats. These data suggest that GABA-B receptor-dependent CRF actions in the VTA mediate stress-induced cocaine seeking and that GABA-B receptor antagonists may have utility for the management of stress-induced relapse in cocaine addicts.
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Affiliation(s)
- Jordan M Blacktop
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI 53233, USA
| | - Oliver Vranjkovic
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI 53233, USA
| | - Matthieu Mayer
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI 53233, USA
| | - Matthew Van Hoof
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI 53233, USA
| | - David A Baker
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI 53233, USA
| | - John R Mantsch
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI 53233, USA.
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Orzeł-Gryglewska J, Matulewicz P, Jurkowlaniec E. Brainstem system of hippocampal theta induction: The role of the ventral tegmental area. Synapse 2015; 69:553-75. [PMID: 26234671 DOI: 10.1002/syn.21843] [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: 12/09/2014] [Revised: 07/03/2015] [Accepted: 07/22/2015] [Indexed: 12/13/2022]
Abstract
This article summarizes the results of studies concerning the influence of the ventral tegmental area (VTA) on the hippocampal theta rhythm. Temporary VTA inactivation resulted in transient loss of the hippocampal theta. Permanent destruction of the VTA caused a long-lasting depression of the power of the theta and it also had some influence on the frequency of the rhythm. Activation of glutamate (GLU) receptors or decrease of GABAergic tonus in the VTA led to enhancement of dopamine release and increased hippocampal theta power. High time and frequency cross-correlation was detected for the theta band between the VTA and hippocampus during paradoxical sleep and active waking. Thus, the VTA may belong to the broad network involved in theta rhythm regulation. This article also presents a model of brainstem-VTA-hippocampal interactions in the induction of the hippocampal theta rhythm. The projections from the VTA which enhance theta rhythm are incorporated into the main theta generation pathway, in which the septum acts as the central node. The neuronal activity that may be responsible for the ability of the VTA to regulate theta probably derives from the structures associated with rapid eye movement (sleep) (REM) sleep or with sensorimotor activity (i.e., mainly from the pedunculopontine and laterodorsal tegmental nuclei and also from the raphe).
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Affiliation(s)
| | - Paweł Matulewicz
- Department of Animal and Human Physiology, University of Gdańsk, Gdańsk, 80-308, Poland
| | - Edyta Jurkowlaniec
- Department of Animal and Human Physiology, University of Gdańsk, Gdańsk, 80-308, Poland
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Draycott B, Loureiro M, Ahmad T, Tan H, Zunder J, Laviolette SR. Cannabinoid transmission in the prefrontal cortex bi-phasically controls emotional memory formation via functional interactions with the ventral tegmental area. J Neurosci 2014; 34:13096-109. [PMID: 25253856 PMCID: PMC6608340 DOI: 10.1523/jneurosci.1297-14.2014] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 08/15/2014] [Accepted: 08/15/2014] [Indexed: 01/01/2023] Open
Abstract
Disturbances in cortical cannabinoid CB1 receptor signaling are well established correlates of various neuropsychiatric disorders, including depression and schizophrenia. Importantly, the ability of cannabinoid transmission to modulate emotional processing is functionally linked to interactions with subcortical DA systems. While considerable evidence demonstrates that CB1 receptor-mediated modulation of emotional processing and related behaviors follows a biphasic functional curve, little is known regarding how CB1 signaling within cortical networks may interact with subcortical DAergic systems involved in emotional behavior regulation. Using a combination of in vivo electrophysiological recordings and behavioral pharmacology in rats, we investigated the relationship between mPFC cannabinoid transmission, fear memory formation, and subcortical DA neuron activity patterns. We report that direct intra-mPFC CB1 activation biphasically modulates spontaneous, subcortical VTA DA neuron activity in a dose-dependent fashion; while lower doses of a CB1 receptor agonist, WIN 55,212-2, significantly increased spontaneous firing and bursting rates of VTA DA neurons, higher doses strongly inhibited spontaneous DA neuron activity. Remarkably, this same dose-related functional difference was observed with the regulation of fear-related emotional memory formation. Thus, lower levels of CB1 activation potentiated the emotional salience of normally subthreshold fear memory, whereas higher levels completely blocked fear memory acquisition. Furthermore, while the potentiation of subthreshold fear memory salience was blocked by DA receptor antagonism, CB1-mediated blunting of suprathreshold fear memory was rescued by intra-VTA administration of a GABAB receptor antagonist, demonstrating that reversal of GABAergic inhibitory mechanisms in the VTA can reverse the inhibitory influence of intra-PFC CB1 transmission on mesolimbic DA activity.
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Affiliation(s)
| | - Michael Loureiro
- Addiction Research Group, Departments of Anatomy and Cell Biology
| | - Tasha Ahmad
- Addiction Research Group, Departments of Anatomy and Cell Biology
| | - Huibing Tan
- Addiction Research Group, Departments of Anatomy and Cell Biology
| | - Jordan Zunder
- Addiction Research Group, Departments of Anatomy and Cell Biology
| | - Steven R Laviolette
- Addiction Research Group, Departments of Anatomy and Cell Biology, Department of Psychiatry, and Department of Psychology, Schulich School of Medicine and Dentistry. University of Western Ontario, London, Ontario, Canada N6A 5C1
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Separate and combined impact of acute naltrexone and alprazolam on subjective and physiological effects of oral d-amphetamine in stimulant users. Psychopharmacology (Berl) 2014; 231:2741-50. [PMID: 24464531 PMCID: PMC4074228 DOI: 10.1007/s00213-014-3449-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Accepted: 01/03/2014] [Indexed: 10/25/2022]
Abstract
RATIONALE Opioid antagonists (e.g., naltrexone) and positive modulators of γ-aminobutyric-acidA (GABAA) receptors (e.g., alprazolam) modestly attenuate the abuse-related effects of stimulants like amphetamine. The use of higher doses to achieve greater efficacy is precluded by side effects. Combining naltrexone and alprazolam might safely maximize efficacy while avoiding the untoward effects of the constituent compounds. OBJECTIVES The present pilot study tested the hypothesis that acute pretreatment with the combination of naltrexone and alprazolam would not produce clinically problematic physiological effects or negative subjective effects and would reduce the positive subjective effects of d-amphetamine to a greater extent than the constituent drugs alone. METHODS Eight nontreatment-seeking, stimulant-using individuals completed an outpatient experiment in which oral d-amphetamine (0, 15, and 30 mg) was administered following acute pretreatment with naltrexone (0 and 50 mg) and alprazolam (0 and 0.5 mg). Subjective effects, psychomotor task performance, and physiological measures were collected. RESULTS Oral d-amphetamine produced prototypical physiological and stimulant-like positive subjective effects (e.g., VAS ratings of Active/Alert/Energetic, Good Effect, and High). Pretreatment with naltrexone, alprazolam, and their combination did not produce clinically problematic acute physiological effects or negative subjective effects. Naltrexone and alprazolam each significantly attenuated some of the subjective effects of d-amphetamine. The combination attenuated a greater number of subjective effects than the constituent drugs alone. CONCLUSIONS The present results support the continued evaluation of an opioid receptor antagonist combined with a GABAA-positive modulator using more clinically relevant experimental conditions like examining the effect of chronic dosing with these drugs on methamphetamine self-administration.
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Frye CA, Koonce CJ, Walf AA. Novel receptor targets for production and action of allopregnanolone in the central nervous system: a focus on pregnane xenobiotic receptor. Front Cell Neurosci 2014; 8:106. [PMID: 24782710 PMCID: PMC3988369 DOI: 10.3389/fncel.2014.00106] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Accepted: 03/25/2014] [Indexed: 12/05/2022] Open
Abstract
Neurosteroids are cholesterol-based hormones that can be produced in the brain, independent of secretion from peripheral endocrine glands, such as the gonads and adrenals. A focus in our laboratory for over 25 years has been how production of the pregnane neurosteroid, allopregnanolone, is regulated and the novel (i.e., non steroid receptor) targets for steroid action for behavior. One endpoint of interest has been lordosis, the mating posture of female rodents. Allopregnanolone is necessary and sufficient for lordosis, and the brain circuitry underlying it, such as actions in the midbrain ventral tegmental area (VTA), has been well-characterized. Published and recent findings supporting a dynamic role of allopregnanolone are included in this review. First, contributions of ovarian and adrenal sources of precursors of allopregnanolone, and the requisite enzymatic actions for de novo production in the central nervous system will be discussed. Second, how allopregnanolone produced in the brain has actions on behavioral processes that are independent of binding to steroid receptors, but instead involve rapid modulatory actions via neurotransmitter targets (e.g., γ-amino butyric acid-GABA, N-methyl-D-aspartate- NMDA) will be reviewed. Third, a recent focus on characterizing the role of a promiscuous nuclear receptor, pregnane xenobiotic receptor (PXR), involved in cholesterol metabolism and expressed in the VTA, as a target for allopregnanolone and how this relates to both actions and production of allopregnanolone will be addressed. For example, allopregnanolone can bind PXR and knocking down expression of PXR in the midbrain VTA attenuates actions of allopregnanolone via NMDA and/or GABAA for lordosis. Our understanding of allopregnanolone’s actions in the VTA for lordosis has been extended to reveal the role of allopregnanolone for broader, clinically-relevant questions, such as neurodevelopmental processes, neuropsychiatric disorders, epilepsy, and aging.
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Affiliation(s)
- Cheryl A Frye
- Department of Psychology, The University at Albany-SUNY Albany, NY, USA ; Department of Biological Sciences, The University at Albany-SUNY Albany, NY, USA ; The Centers for Neuroscience, The University at Albany-SUNY Albany, NY, USA ; Life Sciences Research, The University at Albany-SUNY Albany, NY, USA ; Department of Chemistry and Biochemistry, The University of Alaska-Fairbanks Fairbanks, AK, USA ; Institute of Arctic Biology, The University of Alaska-Fairbanks Fairbanks, AK, USA ; IDeA Network of Biomedical Excellence (INBRE), The University of Alaska-Fairbanks Fairbanks, AK, USA
| | - Carolyn J Koonce
- Department of Psychology, The University at Albany-SUNY Albany, NY, USA ; Institute of Arctic Biology, The University of Alaska-Fairbanks Fairbanks, AK, USA ; IDeA Network of Biomedical Excellence (INBRE), The University of Alaska-Fairbanks Fairbanks, AK, USA
| | - Alicia A Walf
- Department of Psychology, The University at Albany-SUNY Albany, NY, USA ; Institute of Arctic Biology, The University of Alaska-Fairbanks Fairbanks, AK, USA ; IDeA Network of Biomedical Excellence (INBRE), The University of Alaska-Fairbanks Fairbanks, AK, USA
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Frye CA, Koonce CJ, Walf AA. Pregnane xenobiotic receptors and membrane progestin receptors: role in neurosteroid-mediated motivated behaviours. J Neuroendocrinol 2013; 25:1002-11. [PMID: 24028379 PMCID: PMC3943623 DOI: 10.1111/jne.12105] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2013] [Revised: 08/23/2013] [Accepted: 09/05/2013] [Indexed: 10/26/2022]
Abstract
Progestogens have actions in the midbrain ventral tegmental area (VTA) to mediate motivated behaviours, such as those involved in reproductive processes, among female rodents. In the VTA, the formation and actions of one progestogen, 5α-pregnan-3α-ol-20-one (3α,5α-THP), are necessary and sufficient to facilitate sexual responding (measured by lordosis) of female rodents. Although 3α,5α-THP can be produced after metabolism of ovarian progesterone, 3α,5α-THP is also a neurosteroid produced de novo in brain regions, such as the VTA. There can be dynamic changes in 3α,5α-THP production associated with behavioural experience, such as mating. Questions of interest are the sources and targets of 3α,5α-THP. Regarding sources, the pregnane xenobiotic receptor (PXR) may be a novel factor involved in 3α,5α-THP metabolism in the VTA (as well as a direct target of 3α,5α-THP). We have identified PXR in the midbrain of female rats, and manipulating PXR in this region reduces 3α,5α-THP synthesis and alters lordosis, as well as affective and social behaviours. Regarding targets, recent studies have focused on the role of membrane progestin receptors (mPRs). We have analysed the expression of two of the common forms of these receptors (mPRα/paqr7 and mPRβ/paqr8) in female rats. The expression of mPRα was observed in peripheral tissues and brain areas, including the hypothalamus and midbrain. The expression of mPRβ was only observed in brain tissues and was abundant in the midbrain and hypothalamus. To our knowledge, studies of these receptors in mammalian models have been limited to expression and regulation, instead of function. One question that was addressed was the functional effects of progestogens via mPRα and mPRβ in the midbrain of hormone-primed rats for lordosis. Studies to date suggest that mPRβ may be an important target of progestogens in the VTA for lordosis. Taken together, the result of these studies demonstrate that PXR is involved in the production of 3α,5α-THP in the midbrain VTA. Moreover, mPRs may be a target for the actions of progestogens in the VTA for lordosis.
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Affiliation(s)
- C A Frye
- Department of Chemistry, The University of Alaska-Fairbanks, Fairbanks, AK, USA; Institute of Artic Biology, The University of Alaska-Fairbanks, Fairbanks, AK, USA; IDeA Network of Biomedical Excellence (INBRE), The University of Alaska-Fairbanks, Fairbanks, AK, USA
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Relationship between drug discrimination and ratings of subjective effects: implications for assessing and understanding the abuse potential of D-amphetamine in humans. Behav Pharmacol 2013; 24:523-32. [PMID: 23851485 DOI: 10.1097/fbp.0b013e328364505f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The discriminative and subjective effects of drugs in humans are related, but the full extent of this relationship remains to be determined. To further explore this relationship, a retrospective analysis was conducted on data from six studies completed in our laboratory that used identical procedures. The relationship between the discriminative and subjective effects of a range of doses of D-amphetamine (i.e. 2.5-15 mg) was examined using correlational analyses. Significant correlations with discrimination performance were observed on 15 of 20 items from the Drug-Effect Questionnaire across a range of qualities [e.g. Pay For (a positive effect indicative of abuse potential) and Active (a stimulant-like effect)], but the magnitude of these relationships was modest (r<0.52). The current findings demonstrate that diverse subjective effects contribute to the discriminative effects of D-amphetamine and indicate that the former are a more practical means to assess the abuse potential of drugs. Although these procedures are fundamentally related in that they rely on the presence of an interoceptive drug state, they differ in the dimension(s) of the interoceptive effects that participants must quantify. The simultaneous use of drug discrimination and subjective effects may, therefore, reveal complimentary aspects of drug effects that underlie their potential for abuse.
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Ting-A-Kee R, Vargas-Perez H, Mabey JK, Shin SI, Steffensen SC, van der Kooy D. Ventral tegmental area GABA neurons and opiate motivation. Psychopharmacology (Berl) 2013; 227:697-709. [PMID: 23392354 PMCID: PMC4056596 DOI: 10.1007/s00213-013-3002-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Accepted: 01/18/2013] [Indexed: 01/15/2023]
Abstract
RATIONALE Past research has demonstrated that when an animal changes from a previously drug-naive to an opiate-dependent and withdrawn state, morphine's motivational effects are switched from a tegmental pedunculopontine nucleus (TPP)-dependent to a dopamine-dependent pathway. Interestingly, a corresponding change is observed in ventral tegmental area (VTA) GABAA receptors, which change from mediating hyperpolarization of VTA GABA neurons to mediating depolarization. OBJECTIVES The present study investigated whether pharmacological manipulation of VTA GABAA receptor activity could directly influence the mechanisms underlying opiate motivation. RESULTS Using an unbiased place conditioning procedure, we demonstrated that in Wistar rats, intra-VTA administration of furosemide, a Cl(-) cotransporter inhibitor, was able to promote a switch in the mechanisms underlying morphine's motivational properties, one which is normally observed only after chronic opiate exposure. This behavioral switch was prevented by intra-VTA administration of acetazolamide, an inhibitor of the bicarbonate ion-producing carbonic anhydrase enzyme. Electrophysiological recordings of mouse VTA showed that furosemide reduced the sensitivity of VTA GABA neurons to inhibition by the GABAA receptor agonist muscimol, instead increasing the firing rate of a significant subset of these GABA neurons. CONCLUSIONS Our results suggest that the carbonic anhydrase enzyme may constitute part of a common VTA GABA neuron-based biological pathway responsible for controlling the mechanisms underlying opiate motivation, supporting the hypothesis that VTA GABAA receptor hyperpolarization or depolarization is responsible for selecting TPP- or dopamine-dependent motivational outputs, respectively.
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Affiliation(s)
- Ryan Ting-A-Kee
- Institute of Medical Science, Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON, M5S 3E1, Canada.
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Schlussman SD, Buonora M, Brownstein AJ, Zhang Y, Ho A, Kreek MJ. Regional mRNA expression of GABAergic receptor subunits in brains of C57BL/6J and 129P3/J mice: strain and heroin effects. Brain Res 2013; 1523:49-58. [PMID: 23732339 DOI: 10.1016/j.brainres.2013.05.040] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 05/07/2013] [Accepted: 05/24/2013] [Indexed: 12/19/2022]
Abstract
C57BL/6J and 129 substrains of mice are known to differ in their basal levels of anxiety and behavioral response to drugs of abuse. We have previously shown strain differences in heroin-induced conditioned place preference (CPP) between C57BL/6J (C57) and 129P3/J (129) mice, and in the regional expression of several receptor and peptide mRNAs. In this study, we examined the contribution of the GABAergic system in the cortex, nucleus accumbens (NAc), caudate putamen (CPu) and the region containing the substantia nigra and ventral tegmental area (SN/VTA) to heroin reward by measuring mRNA levels of 7 of the most commonly expressed GABA-A receptor subunits, and both GABA-B receptor subunits, in these same mice following saline (control) or heroin administration in a CPP design. Using real-time PCR, we studied the effects of strain and heroin administration on GABA-A α1, α2, α3, β2, and γ2 subunits, which typically constitute synaptic GABA-A receptors, GABA-A α4 and δ subunits, which typically constitute extrasynaptic GABA-A receptors, and GABA-B R1 and R2 subunits. In saline-treated animals, we found an experiment-wise significant strain difference in GABA-Aα2 mRNA expression in the SN/VTA. Point-wise significant strain differences were also observed in GABA-Aα2, GABA-Aα3, and GABA-Aα4 mRNA expression in the NAc, as well as GABA-BR2 mRNA expression in the NAc and CPu, and GABA-BR1 mRNA expression in the cortex. For all differences, 129 mice had higher mRNA expression compared to C57 animals, with the exception of GABA-BR1 mRNA in the cortex where we observed lower levels in 129 mice. Therefore, it may be possible that known behavioral differences between these two strains are, in part, due to differences in their GABAergic systems. While we did not find heroin dose-related changes in mRNA expression levels in C57 mice, we did observe dose-related differences in 129 mice. These results may relate to our earlier behavioral finding that 129 mice are hyporesponsive to the rewarding effects of heroin.
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Affiliation(s)
- S D Schlussman
- The Laboratory of the Biology of Addictive Diseases, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA
| | - M Buonora
- The Laboratory of the Biology of Addictive Diseases, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA
| | - A J Brownstein
- The Laboratory of the Biology of Addictive Diseases, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA
| | - Y Zhang
- The Laboratory of the Biology of Addictive Diseases, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA
| | - A Ho
- The Laboratory of the Biology of Addictive Diseases, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA
| | - M J Kreek
- The Laboratory of the Biology of Addictive Diseases, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA
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Ciccarelli A, Calza A, Panzanelli P, Concas A, Giustetto M, Sassoè-Pognetto M. Organization of GABAergic synaptic circuits in the rat ventral tegmental area. PLoS One 2012; 7:e46250. [PMID: 23056271 PMCID: PMC3466259 DOI: 10.1371/journal.pone.0046250] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Accepted: 08/30/2012] [Indexed: 01/08/2023] Open
Abstract
The ventral tegmental area (VTA) is widely implicated in drug addiction and other psychiatric disorders. This brain region is densely populated by dopaminergic (DA) neurons and also contains a sparse population of γ-aminobutyric acid (GABA)ergic cells that regulate the activity of the principal neurons. Therefore, an in-depth knowledge of the organization of VTA GABAergic circuits and of the plasticity induced by drug consumption is essential for understanding the mechanisms by which drugs induce stable changes in brain reward circuits. Using immunohistochemistry, we provide a detailed description of the localization of major GABAA and GABAB receptor subunits in the rat VTA. We show that DA and GABAergic cells express both GABAA and GABAB receptors. However VTA neurons differ considerably in the expression of GABAA receptor subunits, as the α1 subunit is associated predominantly with non-DA cells, whereas the α3 subunit is present at low levels in both types of VTA neurons. Using an unbiased stereological method, we then demonstrate that α1-positive elements represent only a fraction of non-DA neurons and that the ratio of DA and non-DA cells is quite variable throughout the rostro-caudal extent of the VTA. Interestingly, DA and non-DA cells receive a similar density of perisomatic synapses, whereas axo-dendritic synapses are significantly more abundant in non-DA cells, indicating that local interneurons receive prominent GABAergic inhibition. These findings reveal a differential expression of GABA receptor subtypes in the two major categories of VTA neurons and provide an anatomical basis for interpreting the plasticity of inhibitory circuits induced by drug exposure.
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Affiliation(s)
- Alessandro Ciccarelli
- Department of Anatomy, Pharmacology and Forensic Medicine, University of Turin, and National Institute of Neuroscience-Italy, Torino, Italy
| | - Arianna Calza
- Department of Experimental Biology and Center of Excellence for the Neurobiology of Dependence, University of Cagliari, Cagliari, Italy
| | - Patrizia Panzanelli
- Department of Anatomy, Pharmacology and Forensic Medicine, University of Turin, and National Institute of Neuroscience-Italy, Torino, Italy
| | - Alessandra Concas
- Department of Experimental Biology and Center of Excellence for the Neurobiology of Dependence, University of Cagliari, Cagliari, Italy
| | - Maurizio Giustetto
- Department of Anatomy, Pharmacology and Forensic Medicine, University of Turin, and National Institute of Neuroscience-Italy, Torino, Italy
| | - Marco Sassoè-Pognetto
- Department of Anatomy, Pharmacology and Forensic Medicine, University of Turin, and National Institute of Neuroscience-Italy, Torino, Italy
- * E-mail:
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Ting-A-Kee R, van der Kooy D. The neurobiology of opiate motivation. Cold Spring Harb Perspect Med 2012; 2:2/10/a012096. [PMID: 23028134 DOI: 10.1101/cshperspect.a012096] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Opiates are a highly addictive class of drugs that have been reported to possess both dopamine-dependent and dopamine-independent rewarding properties. The search for how, if at all, these distinct mechanisms of motivation are related is of great interest in drug addiction research. Recent electrophysiological, molecular, and behavioral work has greatly improved our understanding of this process. In particular, the signaling properties of GABA(A) receptors located on GABA neurons in the ventral tegmental area (VTA) appear to be crucial to understanding the interplay between dopamine-dependent and dopamine-independent mechanisms of opiate motivation.
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Affiliation(s)
- Ryan Ting-A-Kee
- Institute of Medical Science, University of Toronto, Terrence Donnelly Centre for Cellular and Biomolecular Research, Toronto, Ontario M5S 3E1, Canada.
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Identification of rat ventral tegmental area GABAergic neurons. PLoS One 2012; 7:e42365. [PMID: 22860119 PMCID: PMC3409171 DOI: 10.1371/journal.pone.0042365] [Citation(s) in RCA: 138] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Accepted: 07/06/2012] [Indexed: 12/29/2022] Open
Abstract
The canonical two neuron model of opioid reward posits that mu opioid receptor (MOR) activation produces reward by disinhibiting midbrain ventral tegmental area (VTA) dopamine neurons through inhibition of local GABAergic interneurons. Although indirect evidence supports the neural circuit postulated by this model, its validity has been called into question by growing evidence for VTA neuronal heterogeneity and the recent demonstration that MOR agonists inhibit GABAergic terminals in the VTA arising from extrinsic neurons. In addition, VTA MOR reward can be dopamine-independent. To directly test the assumption that MOR activation directly inhibits local GABAergic neurons, we investigated the properties of rat VTA GABA neurons directly identified with either immunocytochemistry for GABA or GAD65/67, or in situ hybridization for GAD65/67 mRNA. Utilizing co-labeling with an antibody for the neural marker NeuN and in situ hybridization against GAD65/67, we found that 23±3% of VTA neurons are GAD65/67(+). In contrast to the assumptions of the two neuron model, VTA GABAergic neurons are heterogeneous, both physiologically and pharmacologically. Importantly, only 7/13 confirmed VTA GABA neurons were inhibited by the MOR selective agonist DAMGO. Interestingly, all confirmed VTA GABA neurons were insensitive to the GABAB receptor agonist baclofen (0/6 inhibited), while all confirmed dopamine neurons were inhibited (19/19). The heterogeneity of opioid responses we found in VTA GABAergic neurons, and the fact that GABA terminals arising from neurons outside the VTA are inhibited by MOR agonists, make further studies essential to determine the local circuit mechanisms underlying VTA MOR reward.
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19
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Abstract
Steroid hormones, such as progesterone, are typically considered to be primarily secreted by the gonads (albeit adrenals can also be a source) and to exert their actions through cognate intracellular progestin receptors (PRs). Through its actions in the midbrain ventral tegmental Area (VTA), progesterone mediates appetitive (exploratory, anxiety, social approach) and consummatory (social, sexual) aspects of rodents' mating behaviour. However, progesterone and its natural metabolites ('progestogens') are produced in the midbrain VTA independent of peripheral sources and midbrain VTA of adult rodents is devoid of intracellular PRs. One approach that we have used to understand the effects of progesterone and mechanisms in the VTA for mating is to manipulate the actions of progesterone in the VTA and to examine effects on lordosis (the posture female rodents assume for mating to occur). This review focuses on the effects and mechanisms of progestogens to influence reproduction and related processes. The actions of progesterone and its 5α-reduced metabolite and neurosteroid, 5α-pregnan-3α-ol-20-one (3α,5α-THP; allopregnanolone) in the midbrain VTA to facilitate mating are described. The findings that 3α,5α-THP biosynthesis in the midbrain occurs with mating are discussed. Evidence for the actions of 3α,5α-THP in the midbrain VTA via nontraditional steroid targets is summarised. The broader relevance of these actions of 3α,5α-THP for aspects of reproduction, beyond lordosis, is summarised. Finally, the potential role of the pregnane xenobiotic receptor in mediating 3α,5α-THP biosynthesis in the midbrain is introduced.
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Affiliation(s)
- Cheryl Anne Frye
- Department of Psychology, University at Albany, Albany, NY 12222, USA.
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20
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Diazepam-induced neuronal plasticity attenuates locomotor responses to morphine and amphetamine challenges in mice. Neuroscience 2011; 192:312-21. [DOI: 10.1016/j.neuroscience.2011.07.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Revised: 06/30/2011] [Accepted: 07/01/2011] [Indexed: 11/17/2022]
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21
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Melón LC, Boehm SL. GABAA receptors in the posterior, but not anterior, ventral tegmental area mediate Ro15-4513-induced attenuation of binge-like ethanol consumption in C57BL/6J female mice. Behav Brain Res 2011; 220:230-7. [PMID: 21320533 DOI: 10.1016/j.bbr.2011.02.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2010] [Revised: 02/02/2011] [Accepted: 02/08/2011] [Indexed: 02/05/2023]
Abstract
GABA(A) receptors have been shown to modulate dopaminergic output from the ventral tegmental area (VTA) in studies of both natural and drug rewards, including alcohol. Ro15-4513, the imidazobenzodiazepine derivative and allosteric modulator at the GABA(A) receptor, reliably antagonizes the behavioral effects of alcohol. Various models of alcohol consumption show a decrease in consummatory behaviors, specific to ethanol, following acute administration of the drug. In the present study, Ro15-4513 was systemically administered, or microinjected into the anterior or posterior VTA, to explore the role of GABA(A) receptors at this region in modulating the high pattern of alcohol consumption by C57BL/6J inbred mice in the Drinking in the Dark (DID) model. Animals had 2h access to ethanol for 6 days prior to drug manipulations. Immediately before the seventh day of access, mice were systemically (I.P.) or site-specifically administered Ro15-4513. Systemic Ro15-4513 (at 10mg/kg) decreased binge-like ethanol intake in the DID paradigm. Additionally, there was a stepwise decrease in consumption following Ro15-4513 microinjection into the posterior VTA, with the highest dose significantly decreasing ethanol intake. There was no effect found following microinjection into the anterior VTA, nor was there an effect of systemic or intra-posterior VTA Ro15-4513 on consumption of a 5% sucrose solution or water. The present findings support a role for Ro15-4513 sensitive VTA-GABA(A) receptors in modulating binge-like ethanol consumption. Moreover, the work here adds to the growing body of literature suggesting regional heterogeneity in the VTA.
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Affiliation(s)
- Laverne C Melón
- Psychobiology of Addictions, Department of Psychology, Indiana University/Purdue University-Indianapolis, Indianapolis, IN 46202, USA.
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22
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Orzeł-Gryglewska J, Kuśmierczak M, Jurkowlaniec E. Involvement of GABAergic transmission in the midbrain ventral tegmental area in the regulation of hippocampal theta rhythm. Brain Res Bull 2010; 83:310-20. [DOI: 10.1016/j.brainresbull.2010.09.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2010] [Revised: 08/30/2010] [Accepted: 09/01/2010] [Indexed: 11/15/2022]
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Theile JW, Morikawa H, Gonzales RA, Morrisett RA. GABAergic transmission modulates ethanol excitation of ventral tegmental area dopamine neurons. Neuroscience 2010; 172:94-103. [PMID: 20974231 DOI: 10.1016/j.neuroscience.2010.10.046] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2010] [Revised: 10/14/2010] [Accepted: 10/16/2010] [Indexed: 01/17/2023]
Abstract
Activation of the dopaminergic (DA) neurons of the ventral tegmental area (VTA) by ethanol has been implicated in its rewarding and reinforcing effects. We previously demonstrated that ethanol enhances GABA release onto VTA-DA neurons via activation of 5-HT2C receptors and subsequent release of calcium from intracellular stores. Here we demonstrate that excitation of VTA-DA neurons by ethanol is limited by an ethanol-enhancement in GABA release. In this study, we performed whole-cell voltage clamp recordings of miniature inhibitory postsynaptic currents (mIPSCs) and cell-attached recordings of action potential firing from VTA-DA neurons in midbrain slices from young Long Evans rats. Acute exposure to ethanol (75 mM) transiently enhanced the firing rate of VTA-DA neurons as well as the frequency of mIPSCs. Simultaneous blockade of both GABA(A) and GABA(B) receptors (Picrotoxin (75 μM) and SCH50911 (20 μM)) disinhibited VTA-DA firing rate whereas a GABA(A) agonist (muscimol, 1 μM) strongly inhibited firing rate. In the presence of picrotoxin, ethanol enhanced VTA-DA firing rate more than in the absence of picrotoxin. Additionally, a sub-maximal concentration of muscimol together with ethanol inhibited VTA-DA firing rate more than muscimol alone. DAMGO (3 μM) inhibited mIPSC frequency but did not block the ethanol-enhancement in mIPSC frequency. DAMGO (1 and 3 μM) had no effect on VTA-DA firing rate. Naltrexone (60 μM) had no effect on basal or ethanol-enhancement of mIPSC frequency. Additionally, naltrexone (20 and 60 μM) did not block the ethanol-enhancement in VTA-DA firing rate. Overall, the present results indicate that the ethanol enhancement in GABA release onto VTA-DA neurons limits the stimulatory effect of ethanol on VTA-DA neuron activity and may have implications for the rewarding properties of ethanol.
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Affiliation(s)
- J W Theile
- Cell and Molecular Biology, The College of Pharmacy, The University of Texas at Austin, Austin, TX 78712-1074, USA
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Sun JY, Yang JY, Wang F, Hou Y, Dong YX, Wu CF. GABAA receptors in VTA mediate the morphine-induced release of ascorbic acid in rat nucleus accumbens. Brain Res 2010; 1368:52-8. [PMID: 20965157 DOI: 10.1016/j.brainres.2010.10.029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2010] [Revised: 10/08/2010] [Accepted: 10/10/2010] [Indexed: 10/18/2022]
Abstract
Local perfusion of morphine produces increased levels of extracellular ascorbic acid (AA) in the nucleus accumbens (NAc) of freely moving rats. However, the pathways that regulate morphine-induced AA release in the NAc are unclear. In the present study, we used high performance liquid chromatography with electrochemical detection (HPLC-ECD) to examine the effects of intra-ventral tegmental area (VTA) administration of a GABA(A) agonist and antagonist on morphine-induced increases in AA of the NAc. Also, using high performance liquid chromatography with fluorescent detection (HPLC-FD) and HPLC-ECD, the releases of γ-aminobutyric acid (GABA) and dopamine (DA) in the NAc induced by intra-VTA administration of a GABA(A) agonist and antagonist were also investigated. The results obtained showed that morphine (1 mM), locally perfused into the NAc, significantly increased AA release in the NAc and also GABA release. Intra-VTA infusion of bicuculline (150 ng/rat), a GABA receptor antagonist, not only abolished the enhanced extracellular AA and GABA levels produced by local perfusion of morphine but also decreased the basal release of extracellular GABA and increased the basal release of extracellular DA in the NAc. Muscimol (100 ng/rat), a GABA receptor agonist, affected the basal release of GABA and DA, but not the basal AA levels, or the morphine-induced changes in AA and GABA levels. These findings suggest that the GABA(A) receptors in the VTA play an important role in the modulation of morphine-induced AA release in the NAc, and the effect of morphine on AA release in the NAc is partially regulated by the GABA(A) receptor-mediated action of DA afferents from the VTA.
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Affiliation(s)
- Ji-Ye Sun
- Department of Pharmacology, Shenyang Pharmaceutical University, 110016 Shenyang, PR China
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Miner P, Borkuhova Y, Shimonova L, Khaimov A, Bodnar RJ. GABA-A and GABA-B receptors mediate feeding elicited by the GABA-B agonist baclofen in the ventral tegmental area and nucleus accumbens shell in rats: reciprocal and regional interactions. Brain Res 2010; 1355:86-96. [PMID: 20696149 DOI: 10.1016/j.brainres.2010.07.109] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2010] [Revised: 07/29/2010] [Accepted: 07/30/2010] [Indexed: 11/24/2022]
Abstract
Food intake is significantly increased following administration of GABA-B and GABA-A agonists into the nucleus accumbens (NAC) shell and ventral tegmental area (VTA) with receptor-selective antagonist pretreatment capable of blocking these responses within sites. Regional interactions in feeding studies have been evaluated by administering an antagonist in one site of interest prior to administration of the feeding-active agonist in a second site of interest and have identified important relationships, particularly for opioid-opioid interactions. To evaluate whether regional and reciprocal VTA and NAC shell interactions occur for GABA-mediated feeding, the present study examined whether feeding elicited by the GABA-B agonist, baclofen, microinjected into the NAC shell was dose-dependently blocked by pretreatment with either the GABA-B antagonist, saclofen, or the GABA-A antagonist, bicuculline, into the VTA, and then whether VTA baclofen-induced feeding was dose-dependently blocked by NAC shell pretreatment of either saclofen or bicuculline in rats. Rats were stereotaxically implanted with bilateral pairs of cannulae aimed at the VTA and NAC shell and were assessed for food intake following vehicle and baclofen (200 ng) in each site. Baclofen produced similar magnitudes of increased food intake following VTA and NAC shell treatment. Baclofen administration in the VTA and NAC shell was preceded 20 min earlier with administration of bicuculline (0, 7.5, 75, 150, 300 ng) or saclofen (0, 0.5, 1.5, 3, 5 μg) into the other site with intake measured 1, 2 and 4h after agonist treatment. VTA saclofen dose-dependently and significantly blocked feeding elicited by NAC shell baclofen. Correspondingly, NAC shell saclofen dose-dependently and significantly blocked feeding elicited by VTA baclofen, indicating a robust and bidirectional GABA-B/GABA-B receptor interaction between sites. Whereas VTA bicuculline significantly blocked the increased feeding elicited by NAC shell baclofen, NAC shell bicuculline reduced but did not block feeding elicited by VTA baclofen, indicating a unidirectional interaction GABA-B/GABA-A receptor interaction between sites. Unlike within-site receptor specificity governing the ability of GABA agonist mediation of food intake, the present study demonstrates that GABA, like opioids, employs a distributed brain network in mediating its ingestive effects, and that under certain circumstances, uses multiple receptor subtypes to underlie its regional effects.
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Affiliation(s)
- Patricia Miner
- Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, Flushing, NY 11367, USA
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Blum K, Chen TJ, Downs BW, Bowirrat A, Waite RL, Braverman ER, Madigan M, Oscar-Berman M, DiNubile N, Gold M. Neurogenetics of dopaminergic receptor supersensitivity in activation of brain reward circuitry and relapse: proposing "deprivation-amplification relapse therapy" (DART). Postgrad Med 2009; 121:176-96. [PMID: 19940429 PMCID: PMC3656125 DOI: 10.3810/pgm.2009.11.2087] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND AND HYPOTHESIS It is well known that after prolonged abstinence, individuals who use their drug of choice experience a powerful euphoria that often precipitates relapse. While a biological explanation for this conundrum has remained elusive, we hypothesize that this clinically observed "supersensitivity" might be tied to genetic dopaminergic polymorphisms. Another therapeutic conundrum relates to the paradoxical finding that the dopaminergic agonist bromocriptine induces stronger activation of brain reward circuitry in individuals who carry the DRD2 A1 allele compared with DRD2 A2 allele carriers. Because carriers of the A1 allele relative to the A2 allele of the DRD2 gene have significantly lower D2 receptor density, a reduced sensitivity to dopamine agonist activity would be expected in the former. Thus, it is perplexing that with low D2 density there is an increase in reward sensitivity with the dopamine D2 agonist bromocriptine. Moreover, under chronic or long-term therapy with D2 agonists, such as bromocriptine, it has been shown in vitro that there is a proliferation of D2 receptors. One explanation for this relates to the demonstration that the A1 allele of the DRD2 gene is associated with increased striatal activity of L-amino acid decarboxylase, the final step in the biosynthesis of dopamine. This appears to be a protective mechanism against low receptor density and would favor the utilization of an amino acid neurotransmitter precursor like L-tyrosine for preferential synthesis of dopamine. This seems to lead to receptor proliferation to normal levels and results in significantly better treatment compliance only in A1 carriers. PROPOSAL AND CONCLUSION We propose that low D2 receptor density and polymorphisms of the D2 gene are associated with risk for relapse of substance abuse, including alcohol dependence, heroin craving, cocaine dependence, methamphetamine abuse, nicotine sensitization, and glucose craving. With this in mind, we suggest a putative physiological mechanism that may help to explain the enhanced sensitivity following intense acute dopaminergic D2 receptor activation: "denervation supersensitivity." Rats with unilateral depletions of neostriatal dopamine display increased sensitivity to dopamine agonists estimated to be 30 to 100 x in the 6-hydroxydopamine (6-OHDA) rotational model. Given that mild striatal dopamine D2 receptor proliferation occurs (20%-40%), it is difficult to explain the extent of behavioral supersensitivity by a simple increase in receptor density. Thus, the administration of dopamine D2 agonists would target D2 sensitization and attenuate relapse, especially in D2 receptor A1 allele carriers. This hypothesized mechanism is supported by clinical trials utilizing amino acid neurotransmitter precursors, enkephalinase, and catechol-O-methyltransferase (COMT) enzyme inhibition, which have resulted in attenuated relapse rates in reward deficiency syndrome (RDS) probands. If future translational research reveals that dopamine agonist therapy reduces relapse in RDS, it would support the proposed concept, which we term "deprivation-amplification relapse therapy" (DART). This term couples the mechanism for relapse, which is "deprivation-amplification," especially in DRD2 A1 allele carriers with natural D2 agonist therapy utilizing amino acid precursors and COMT and enkepalinase inhibition therapy.
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Affiliation(s)
- Kenneth Blum
- Department of Psychiatry, School of Medicine, University of Florida, Gainesville, FL
- Department of Nutrigenomics, LifeGen, Inc., San Diego, CA and Lederach, PA
| | - Thomas J.H. Chen
- Department of Health and Occupational Safety, Chang Jung Christian University, Taiwan, Republic of China
| | - B. William Downs
- Department of Nutrigenomics, LifeGen, Inc., San Diego, CA and Lederach, PA
| | - Abdalla Bowirrat
- Clinical Neuroscience & Population Genetics, Ziv Government Medical Center, Israel
| | - Roger L. Waite
- Department of Nutrigenomics, LifeGen, Inc., San Diego, CA and Lederach, PA
| | - Eric R. Braverman
- Department of Neurosurgery, Weill Cornell College of Medicine, New York, NY
| | - Margaret Madigan
- Department of Nutrigenomics, LifeGen, Inc., San Diego, CA and Lederach, PA
| | | | - Nicholas DiNubile
- Department of Orthopedic Surgery, Hospital of the University of Pennsylvania, Philadelphia, PA
| | - Mark Gold
- Department of Psychiatry, School of Medicine, University of Florida, Gainesville, FL
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Kawahara Y, Kawahara H, Kaneko F, Yamada M, Nishi Y, Tanaka E, Nishi A. Peripherally administered ghrelin induces bimodal effects on the mesolimbic dopamine system depending on food-consumptive states. Neuroscience 2009; 161:855-64. [DOI: 10.1016/j.neuroscience.2009.03.086] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Revised: 03/11/2009] [Accepted: 03/28/2009] [Indexed: 12/01/2022]
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Ding ZM, Liu W, Engleman EA, Rodd ZA, McBride WJ. Differential effects of dopamine D2 and GABA(A) receptor antagonists on dopamine neurons between the anterior and posterior ventral tegmental area of female Wistar rats. Pharmacol Biochem Behav 2009; 92:404-12. [PMID: 19480073 PMCID: PMC2859430 DOI: 10.1016/j.pbb.2009.01.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Previous findings indicated differences in neuronal circuitries mediating drug reinforcement between the anterior and posterior ventral tegmental area (VTA). The objective of the present study was to examine the effects of the dopamine D2 antagonist sulpiride and the GABA(A) antagonist picrotoxin administered in the anterior and posterior VTA on the activity of mesoaccumbal dopamine neurons in female Wistar rats. Sulpiride and picrotoxin were administered in the anterior and posterior VTA. Extracellular dopamine levels were measured in sub-regions of the VTA and nucleus accumbens (ACB). Reverse-microdialysis of sulpiride (100 microM) into the posterior VTA increased extracellular dopamine levels locally (80% above baseline) and in the ACB shell and core (70% above baseline), whereas reverse-microdialysis into the anterior VTA produced a much smaller effect locally (30% above baseline) and in the ACB shell and core. In contrast, microinjection of picrotoxin (80 and 160 microM) into the anterior, but not posterior VTA, increased dopamine release in the ACB shell. The results suggest that dopamine neurons in the posterior VTA, compared to the anterior VTA, may be under greater D2 receptor-mediated tonic inhibition, whereas dopamine neurons in the anterior VTA, compared to the posterior VTA, may be under greater GABA(A) receptor-mediated tonic inhibition.
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Affiliation(s)
- Zheng-Ming Ding
- Indiana University School of Medicine, Institute of PsychiatricResearch, 791 Union Drive, Indianapolis, IN 46202-4887, USA.
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Ting-A-Kee R, Dockstader C, Heinmiller A, Grieder T, van der Kooy D. GABAAreceptors mediate the opposing roles of dopamine and the tegmental pedunculopontine nucleus in the motivational effects of ethanol. Eur J Neurosci 2009; 29:1235-44. [DOI: 10.1111/j.1460-9568.2009.06684.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Frye CA, Walf AA. Membrane actions of progestins at dopamine type 1-like and GABAA receptors involve downstream signal transduction pathways. Steroids 2008; 73:906-13. [PMID: 18342351 PMCID: PMC2492830 DOI: 10.1016/j.steroids.2008.01.020] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2007] [Revised: 01/14/2008] [Accepted: 01/28/2008] [Indexed: 12/27/2022]
Abstract
In the ventral tegmental area (VTA), progestins facilitate lordosis via rapid actions at membrane dopamine Type 1-like (D(1)) and/or GABA(A) receptors (GBRs), rather than via cognate, intracellular progestin receptors (PRs). Downstream signal transduction pathways involved in these effects were investigated using lordosis as a bioassay. If progestins' actions at D(1) and/or GBRs in the VTA require activation of G-proteins, adenylyl cyclase, cyclic AMP-dependent protein kinase A (PKA), phospholipase C (PLC), and/or PKC, then pharmacologically blocking these pathways would be expected to attenuate progestin-facilitated lordosis and its enhancement by D(1) and GBR activity. Ovariectomized, estradiol-primed rats were infused first with vehicle or signal transduction inhibitor, and second with vehicle, a D(1) or GBR agonist, and then with vehicle or progestins to the VTA. Rats were tested for lordosis following infusions. Results indicated that initiation of G-proteins, adenylyl cyclase, PKA, PLC, or PKC in the VTA is required for rapid effects of progestins through D(1) and/or GBRs to facilitate lordosis. As well, progestins' actions at n-methyl-d-aspartate receptors (NMDARs) may modulate activity at D(1) and/or GBRs and mitogen activated protein kinase (MAPK) may be a common signaling pathway. Findings from a microarray study demonstrated that there was upregulation of genes associated with steroid metabolism, GBRs, D(1), NMDARs and signal transduction factors in the midbrain VTA of naturally receptive mated compared to non-mated rats. Thus, in the VTA, progestins have rapid membrane-mediated actions via D(1), GBRs, NMDARs and their downstream signal transduction pathways.
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Affiliation(s)
- Cheryl A Frye
- Department of Psychology, The University at Albany, SUNY, Albany, NY 12222, USA.
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31
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Juárez I, Gratton A, Flores G. Ontogeny of altered dendritic morphology in the rat prefrontal cortex, hippocampus, and nucleus accumbens following Cesarean delivery and birth anoxia. J Comp Neurol 2008; 507:1734-47. [PMID: 18253967 DOI: 10.1002/cne.21651] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We used a delayed Cesarean birth model and the Golgi-Cox staining method to investigate the effects of perinatal anoxia on prefrontal cortex (PFC) and hippocampal (CA1) pyramidal neurons as well as nucleus accumbens (NAcc) medium spiny neurons. Dendritic morphology in these regions was studied on postnatal days (P) 2, 7, 14, 21, 35, and 70 in male Sprague-Dawley rats born either vaginally (VAG) or by Cesarean section either with (C + anoxia) or without (C-only) anoxia. The most striking birth group differences seen were at the level of dendritic spine densities on P35. During this postnatal period the dendritic spine density of PFC neurons was significantly lower in C + anoxia and C-only animals than in VAG controls; however, by P70 PFC spine densities in all birth groups were comparable. In contrast, hippocampal spine densities on P35 were comparably greater in C + anoxia animals than in VAG controls, whereas in C-only animals spine densities were lower than controls; here again, by P70 all groups had comparable hippocampal spine densities. In NAcc greater spine densities were seen on medium spiny neurons of C + anoxia animals on P35. These findings provide evidence that perinatal insult in the form of Cesarean birth with or without anoxia alters the dendritic development of PFC and hippocampal pyramidal neurons and to some extent also of NAcc medium spiny neurons. They also suggest that perinatal anoxia can alter the neuronal development of key structures thought to be affected in such late-onset dopamine-related disorders as schizophrenia and Attention Deficit Hyperactivity Disorder (ADHD).
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Affiliation(s)
- Ismael Juárez
- Laboratorio de Neuropsiquiatría, Instituto de Fisiología, Universidad Autónoma de Puebla, Puebla 72570, México
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Howell LL, Kimmel HL. Monoamine transporters and psychostimulant addiction. Biochem Pharmacol 2007; 75:196-217. [PMID: 17825265 DOI: 10.1016/j.bcp.2007.08.003] [Citation(s) in RCA: 148] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2007] [Revised: 07/25/2007] [Accepted: 08/02/2007] [Indexed: 12/27/2022]
Abstract
Psychostimulants are a broadly defined class of drugs that stimulate the central and peripheral nervous systems as their primary pharmacological effect. The abuse liability of psychostimulants is well established and represents a significant public health concern. An extensive literature documents the critical importance of monoamines (dopamine, serotonin and norepinephrine) in the behavioral pharmacology and addictive properties of psychostimulants. In particular, the dopamine transporter plays a primary role in the reinforcing and behavioral-stimulant effects of psychostimulants in animals and humans. Moreover, both serotonin and norepinephrine systems can reliably modulate the neurochemical and behavioral effects of psychostimulants. However, there is a growing body of evidence that highlights complex interactions among additional neurotransmitter systems. Cortical glutamatergic systems provide important regulation of dopamine function, and inhibitory amino acid gamma-aminobutyric acid (GABA) systems can modulate basal dopamine and glutamate release. Repeated exposure to psychostimulants can lead to robust and enduring changes in neurobiological substrates, including monoamines, and corresponding changes in sensitivity to acute drug effects on neurochemistry and behavior. Significant advances in the understanding of neurobiological mechanisms underlying psychostimulant abuse and dependence have guided pharmacological treatment strategies to improve clinical outcome. In particular, functional agonist treatments may be used effectively to stabilize monoamine neurochemistry, influence behavior and lead to long-term abstinence. However, additional clinical studies are required in order to identify safe and efficacious pharmacotherapies.
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Affiliation(s)
- Leonard L Howell
- Division of Neuroscience, Yerkes National Primate Research Center, Emory University, 954 Gatewood Road NE, Atlanta, GA 30329, USA.
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Doherty M, Gratton A. Differential involvement of ventral tegmental GABA(A) and GABA(B) receptors in the regulation of the nucleus accumbens dopamine response to stress. Brain Res 2007; 1150:62-8. [PMID: 17395162 DOI: 10.1016/j.brainres.2007.02.081] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2006] [Revised: 02/20/2007] [Accepted: 02/23/2007] [Indexed: 10/23/2022]
Abstract
Evidence indicates that dopamine (DA) transmission in nucleus accumbens (NAcc) is modulated by glutamate (GLUT) projections from medial prefrontal cortex (PFC) to NAcc and the ventral tegmental area (VTA). Local NMDA receptor blockade in NAcc has previously been shown to enhance the DA stress response in this region as well as in the VTA. This raises the possibility that the NAcc DA stress response is regulated by GLUT acting at NMDA receptors located on NAcc GABA output neurons that project to the VTA where GABA is known to regulate DA cell activity. Thus, in the present study, we used voltammetry to examine the effects of intra-VTA administration of GABA(A) and GABA(B) agonists and antagonists on restraint stress-induced increases in NAcc DA. The results show that local VTA GABA(B) receptor activation with baclofen (0.01, 0.1 and 1.0 nmol) dose-dependently inhibited the NAcc DA stress response whereas GABA(B) receptor blockade with phaclofen had the opposite effect, resulting in a dose-dependent potentiation of the stress response. A similar potentiation of the NAcc DA stress response was observed following VTA GABA(A) receptor blockade with bicuculline, but only at the highest dose (1.0 nmol). Interestingly, intra-VTA injection of the GABA(A) receptor agonist, muscimol, at the lowest dose (0.01 nmol) but not at the higher doses (0.1 or 1.0 nmol) also potentiated the NAcc DA stress response, suggesting an action mediated primarily at GABA(A) receptors located on non-DA neurons. These results indicate that the NAcc DA stress response is regulated by GABA afferents to VTA DA cells and that this action is differentially mediated by GABA(A) and GABA(B) receptors. The data suggest that the relevant GABA(B) receptors are located on DA neurons whereas the GABA(A) receptors are located on GABA interneurons and perhaps also on DA cells. The present findings are also consistent with the idea that the corticofugal GLUT input to NAcc indirectly regulates stress-induced DA release in this region through the GABA feedback pathway to VTA.
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Affiliation(s)
- Michael Doherty
- Douglas Hospital Research Center, Department of Psychiatry, McGill University, 6875 LaSalle Blvd, Montréal Verdun, Québec, Canada, H4H 1R3
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Petralia SM, DeBold JF, Frye CA. MK-801 infusions to the ventral tegmental area and ventromedial hypothalamus produce opposite effects on lordosis of hormone-primed rats. Pharmacol Biochem Behav 2007; 86:377-85. [PMID: 17292951 PMCID: PMC3622250 DOI: 10.1016/j.pbb.2007.01.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2006] [Revised: 10/06/2006] [Accepted: 01/08/2007] [Indexed: 10/23/2022]
Abstract
Progesterone initiates female sexual behavior of rodents (lordosis) through actions at intracellular progestin receptors in the ventromedial hypothalamus. Progesterone's metabolite, 5alpha-pregnan-3alpha-ol-20-one, mediates the intensity and duration of lordosis through its actions at GABA(A) receptors in the ventral tegmental area. Whether progestins can influence sexual behavior through actions that involve N-methyl-D-aspartate receptors (NMDARs) in the ventromedial hypothalamus and ventral tegmental area was investigated. The current study examines the effect of bilateral ventral tegmental area or ventromedial hypothalamus infusions of the non-competitive NMDAR antagonist (+)-MK-801 hydrogen maleate (MK-801; 0, 20, or 200 ng) on lordosis, motor activity, and NMDA R1 subtype (NMDAR1) immunoreactivity in estradiol benzoate (10 microg)+progesterone (50 microg)- and estradiol benzoate+vehicle primed rats. Compared to vehicle infusions, infusions of MK-801 to the ventral tegmental area facilitated lordosis of estradiol benzoate (10 microg)+progesterone (50 microg)- and estradiol benzoate+vehicle primed rats. Infusions of MK-801 to the ventromedial hypothalamus inhibited lordosis of estradiol benzoate (10 microg)+progesterone (50 microg)- and estradiol benzoate+vehicle primed rats, compared to vehicle. There was no effect of MK-801 infusions to the ventral tegmental area or the ventromedial hypothalamus on motor behavior. Immunocytochemistry for NMDAR1 revealed MK-801 (200 ng) infusions to the ventral tegmental area or ventromedial hypothalamus of estradiol benzoate (10 microg)+progesterone (50 microg)- or estradiol benzoate+vehicle primed rats significantly reduced the number of darkly stained NMDAR1-immunoreactive cells, compared to vehicle infusions. These data suggest NMDARs may be important in the mediation of hormonal actions in both the ventral tegmental area and the ventromedial hypothalamus for sexual receptivity of rodents, but in different ways.
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Affiliation(s)
- Sandra M. Petralia
- Department of Psychology, The University at Albany-SUNY, Albany, NY, USA
| | | | - Cheryl A. Frye
- Department of Psychology, The University at Albany-SUNY, Albany, NY, USA
- Biological Sciences, The University at Albany-SUNY, Albany, NY, USA
- Center for Life Science, The University at Albany-SUNY, Albany, NY, USA
- Center for Neuroscience Research, The University at Albany-SUNY, Albany, NY, USA
- Corresponding author. Department of Psychology, The University at Albany-SUNY, Life Sciences Research Building 01058, 1400 Washington Avenue, Albany, NY 12222, USA. Tel.: +1 518 591 8839; fax: +1 518 591 8848. (C.A. Frye)
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Frye CA, Walf AA, Petralia SM. In the ventral tegmental area, progestins have actions at D1 receptors for lordosis of hamsters and rats that involve GABA A receptors. Horm Behav 2006; 50:332-7. [PMID: 16750831 DOI: 10.1016/j.yhbeh.2006.04.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2005] [Revised: 04/14/2006] [Accepted: 04/18/2006] [Indexed: 10/24/2022]
Abstract
In the ventral tegmental area (VTA), progestins facilitate lordosis via actions at gamma-aminobutyric acid (GABA)(A)/benzodiazepine receptor complexes (GBRs) and dopamine type 1 receptors (D1). The relationship between progestins' actions at GBRs and D1 in the VTA for facilitating sexual behavior of hamsters and rats was examined. Ovariectomized (ovx), estradiol (E(2); 10 microg)+progesterone (P; 250 microg; SC)-primed hamsters, with bilateral guide cannulae to the VTA, were pre-tested for sexual and motor behavior and infused with the GBR antagonist bicuculline (100 ng/side) or vehicle. Thirty minutes later, hamsters were re-tested and then infused with the D1 agonist SKF38393 (100 ng/side) or vehicle. Hamsters were post-tested 30 min later. Ovx, E(2) (10 microg)-primed rats were pre-tested, infused first with bicuculline or vehicle, second with SKF38393 or vehicle, third with 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP; 0, 100, or 200 ng) and were post-tested 10 and 60 min after 3alpha,5alpha-THP infusions. VTA infusions of SKF38393 increased lordosis of hamsters or rats. Bicuculline pretreatment reduced SKF38393- and/or progesterone-mediated increases in lordosis of E2-primed hamsters. In E2-primed rats, bicuculline blocked SKF38393- and/or 3alpha,5alpha-THP-mediated increases in lordosis. There were no effects on motor behavior. Thus, in the VTA, GBR activity modulates D1-mediated actions for lordosis of hamsters and rats.
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MESH Headings
- 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/administration & dosage
- 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/pharmacology
- Animals
- Bicuculline/pharmacology
- Cricetinae
- Desoxycorticosterone/administration & dosage
- Desoxycorticosterone/analogs & derivatives
- Desoxycorticosterone/pharmacology
- Dopamine Agonists/administration & dosage
- Dopamine Agonists/pharmacology
- Female
- GABA Antagonists/pharmacology
- Injections
- Male
- Motor Activity/drug effects
- Posture
- Progestins/pharmacology
- Rats
- Rats, Long-Evans
- Receptors, Dopamine D1/drug effects
- Receptors, GABA-A/physiology
- Sexual Behavior, Animal/drug effects
- Species Specificity
- Steroids/administration & dosage
- Steroids/pharmacology
- Ventral Tegmental Area/drug effects
- Ventral Tegmental Area/physiology
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Affiliation(s)
- Cheryl A Frye
- Department of Psychology, The University at Albany-SUNY, Albany, NY 12222, USA.
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Petralia SM, Frye CA. In the ventral tegmental area, G-proteins mediate progesterone's actions at dopamine type 1 receptors for lordosis of rats and hamsters. Psychopharmacology (Berl) 2006; 186:133-42. [PMID: 16482481 DOI: 10.1007/s00213-006-0311-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2005] [Accepted: 12/22/2005] [Indexed: 11/27/2022]
Abstract
RATIONALE Previous reports indicate that the ventral tegmental area (VTA) and/or progesterone (P) can modulate the reinforcing effects of drugs of abuse, food, and sexual behavior. OBJECTIVES We investigated if, in the VTA, P's membrane-mediated actions for lordosis involve dopamine type 1 receptors (D(1)). Also, whether P's actions at D(1) for lordosis are mediated by typical G-protein coupled mechanisms was examined. METHODS In Exps 1 and 2, rats received estradiol (E(2) 10 microg) at h 0 and infusions of the D(1) antagonist SCH23390 (100 ng), the D(1) agonist SKF38393 (100 ng), or vehicle, to the VTA, at h 44. Thirty minutes later, rats received systemic P (0, 50, 100, or 200 microg). Subjects were tested for lordosis and motor behavior 2.5 h later. In Exps 3 and 4, E(2)+P (rats 0 or 100 microg; hamsters 200 microg)-primed animals were pretested for lordosis and motor behavior at h 47.5 and infused with SKF38393 (100 ng) or vehicle to the VTA. Thirty minutes later, subjects were retested and infused with the G-protein inhibitor guanosine 5'-O-(2-Thiodiphosphate) (GDP-beta-S; 50 microM) or vehicle. Post-testing occurred 30 min later. RESULTS Pretreatment with SCH23390-reduced and SKF38393-enhanced P's actions, in the VTA, for lordosis of E(2)-primed rats and hamsters. As well, D(1)-mediated increases in P-facilitated lordosis of rats and hamsters were inhibited by GDP-beta-S. Changes in lordosis were independent of large alterations in motor behavior. CONCLUSIONS In the VTA, P has actions for modulating reinforcing behaviors, such as lordosis, at D(1) that are G-protein-mediated.
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MESH Headings
- 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/pharmacology
- Animals
- Behavior, Animal/drug effects
- Behavior, Animal/physiology
- Benzazepines/pharmacology
- Cricetinae
- Dopamine Agonists/pharmacology
- Dopamine Antagonists/pharmacology
- Female
- GTP-Binding Proteins/metabolism
- Lordosis/metabolism
- Lordosis/physiopathology
- Motor Activity/drug effects
- Motor Activity/physiology
- Ovariectomy
- Progesterone/pharmacology
- Rats
- Rats, Long-Evans
- Receptors, Dopamine D1/agonists
- Receptors, Dopamine D1/antagonists & inhibitors
- Receptors, Dopamine D1/metabolism
- Ventral Tegmental Area/drug effects
- Ventral Tegmental Area/metabolism
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Affiliation(s)
- Sandra M Petralia
- Department of Psychology, The University at Albany, SUNY, Albany, NY, 12222, USA
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Filip M, Frankowska M, Gołda A, Zaniewska M, Vetulani J, Przegaliński E. Various GABA-mimetic drugs differently affect cocaine-evoked hyperlocomotion and sensitization. Eur J Pharmacol 2006; 541:163-70. [PMID: 16777090 DOI: 10.1016/j.ejphar.2006.05.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2006] [Revised: 05/04/2006] [Accepted: 05/09/2006] [Indexed: 11/22/2022]
Abstract
To substantiate the notion that cocaine behavioral effects may be influenced by gamma-aminobutyric acid (GABA) neurotransmission male Wistar rats were injected with gabapentin (a cyclic GABA analogue), tiagabine (a GABA reuptake inhibitor), or vigabatrin (a GABA transaminase inhibitor) before acute or repeated treatment with cocaine evoking either locomotor hyperactivation or sensitization. Gabapentin (1-30 mg/kg), tiagabine (2.5-10 mg/kg) or vigabatrin (75-250 mg/kg) attenuated the cocaine (10 mg/kg)-induced hyperactivation and in the highest doses they also decreased basal locomotor activation. Vigabatrin (75-250 mg/kg) dose-dependently reduced the development of cocaine sensitization in rats treated repeatedly (days 1-5) with cocaine (10 mg/kg) and then challenged with cocaine (10 mg/kg) following 5-day withdrawal; the remaining drugs were ineffective. When injected acutely with a cocaine challenge dose, gabapentin (3-10 mg/kg) or vigabatrin (150 mg/kg), but not tiagabine, significantly attenuated the expression of cocaine sensitization. The present results show that enhanced GABA-ergic neurotransmission exerted inhibitory actions on acute responses to cocaine, however, only in a case of vigabatrin the inhibition seems to be unrelated to the inhibitory effect of the drugs on basal locomotor activity. The finding that vigabatrin protected against the development and the expression of cocaine sensitization further supports its therapeutic potential in the treatment of cocaine dependence.
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Affiliation(s)
- Małgorzata Filip
- Department of Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, Smetna, Poland.
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White WD, Crockford D, Patten S, El-Guebaly N. A randomized, open-label pilot comparison of gabapentin and bupropion SR for smoking cessation. Nicotine Tob Res 2006; 7:809-13. [PMID: 16191752 DOI: 10.1080/14622200500259887] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
This 6-week, randomized, open-label pilot study estimated the treatment effect size of gabapentin (n = 17) compared with bupropion SR (n = 19) for smoking cessation, thereby allowing sample size calculations for a definitive comparison study. The primary outcome measure was smoking cessation. Secondary outcome measures included smoking reduction and withdrawal severity. Gabapentin was less efficacious than bupropion for smoking cessation but was associated with fewer dropouts from adverse effects. Withdrawal severity was less with bupropion. Bupropion remains the first-line non-nicotine pharmacotherapy for smoking cessation. Further study is required to determine if gabapentin has any useful role in smoking cessation. Based on our primary outcome measure, 79 subjects would be required in each treatment group of a two-armed study to achieve 90% power for detecting a difference in efficacy between gabapentin and bupropion.
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Bartoletti M, Gubellini C, Ricci F, Gaiardi M. Baclofen blocks the development of sensitization to the locomotor stimulant effect of amphetamine. Behav Pharmacol 2005; 16:553-8. [PMID: 16170232 DOI: 10.1097/01.fbp.0000179279.98029.e9] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The GABAB agonist baclofen (BCF) has recently been reported to block the expression of sensitization to the locomotor effect of amphetamine (AMPH), and to reverse it after repeated administration. The present study was undertaken to investigate whether baclofen could also prevent the development of sensitization to the psychostimulant. Chronic AMPH treatment (1.5 mg/kg i.p. for 10 days) led to an increased locomotor response to AMPH (1.5 mg/kg) when the animals were challenged 3 and 30 days after the end of repeated treatment. Chronic co-administration of BCF (2 mg/kg, i.p.) and AMPH blocked the development of sensitization to the stimulant effect of AMPH. An ancillary experiment excluded that a 'state-dependency' hypothesis could account for the effect of baclofen. Furthermore, a previous repeated treatment with baclofen alone had no influence either on the acute AMPH effect or on the subsequent development of sensitization to AMPH. In conclusion, the results confirm that GABAB receptors play an important role in the acquisition of AMPH behavioural sensitization and further support a potential use of GABAB agonists in the treatment of psychostimulant addiction.
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Affiliation(s)
- M Bartoletti
- Department of Pharmacology, University of Bologna, Via Irnerio 48, I-40126 Bologna, Italy.
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Walker BM, Ettenberg A. Intra-ventral tegmental area heroin-induced place preferences in rats are potentiated by peripherally administered alprazolam. Pharmacol Biochem Behav 2005; 82:470-7. [PMID: 16297973 DOI: 10.1016/j.pbb.2005.10.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2005] [Revised: 09/29/2005] [Accepted: 10/08/2005] [Indexed: 11/20/2022]
Abstract
The present experiment was designed to replicate and extend previous results of an opiate+benzodiazepine interaction in which peripherally administered alprazolam was observed to modulate behavior resulting from intravenous injections of heroin. As a first step in determining the role of central sites in this drug interaction, changes in drug reward (measured by conditioned place preference; CPP) were assessed in rats given systemic administration of alprazolam coupled with intracranially infused heroin (into the ventral tegmental area; VTA). Sprague-Dawley rats were implanted with guide cannula targeting the VTA, after which a heroin-induced CPP dose-response curve was determined (2.5-40 ng administered bilaterally in 0.5 microl/side). In other animals, intra-VTA heroin-induced place preferences were challenged with systemically applied alprazolam (0.125 mg/kg i.p.). The data confirm that rats dose-dependently develop reliable place preferences for a distinct environment paired with bilateral VTA-infusions of heroin. Additionally, when a non-rewarding dose of alprazolam was combined with a non-rewarding bilateral intra-VTA heroin dose (5 ng), a significant CPP was produced. These data extend earlier results by demonstrating that a systemically applied benzodiazepine can enhance the rewarding effects produced by central opiate administration. The results suggest that the VTA might be a site where this opiate+benzodiazepine interaction occurs.
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Affiliation(s)
- Brendan M Walker
- Behavioral Pharmacology Laboratory, Department of Psychology, University of California, Santa Barbara, CA 93106, United States
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41
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Steiniger-Brach B, Kretschmer BD. Different function of pedunculopontine GABA and glutamate receptors in nucleus accumbens dopamine, pedunculopontine glutamate and operant discriminative behavior. Eur J Neurosci 2005; 22:1720-30. [PMID: 16197512 DOI: 10.1111/j.1460-9568.2005.04361.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The nucleus accumbens, as the main input structure of the ventral basal ganglia loop, is described as a limbic-motor interface. Dopamine input to nucleus accumbens modulates processing of concurrent glutamate input from limbic structures carrying motor and motivational information. There is evidence that these dopamine/glutamate interactions are fundamentally involved in response selection processes. However, the pedunculopontine tegmental nucleus (PPTg) in the brainstem is connected with limbic structures as well as dopaminergic midbrain areas, which also project to the nucleus accumbens. Furthermore, behavioral studies implicate the PPTg in complex, motivated behavior. Thus, the PPTg might be involved in motivated behavior by influencing response selection processes in the nucleus accumbens. In this study we used in vivo microdialysis in freely moving rats in order to inhibit (100, 200, 300 and 400 microm baclofen) or stimulate [5, 12.5, 25 or 50 micromalpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA)] the PPTg in animals that are performing an operant discrimination task for food reward. The behavioral consequences were correlated with dopamine and glutamate levels in nucleus accumbens and PPTg, respectively. PPTg inhibition by local GABAB receptors impaired the response rate and accuracy of performance in the operant discrimination task. PPTg stimulation by local AMPA receptors exclusively impaired the response rate. Both treatments blocked the performance-driven dopamine signal in nucleus accumbens, whereas glutamate in PPTg was enhanced after AMPA administration only. The data indicate that the PPTg functionally participates in a network of subcortical and cortical structures, which is responsible for the execution of motivated behavior and response selection processes.
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42
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Stromberg MF. The effect of baclofen alone and in combination with naltrexone on ethanol consumption in the rat. Pharmacol Biochem Behav 2005; 78:743-50. [PMID: 15301930 DOI: 10.1016/j.pbb.2004.05.006] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2003] [Revised: 05/12/2004] [Accepted: 05/14/2004] [Indexed: 11/29/2022]
Abstract
Naltrexone has been evaluated in preclinical animal models of ethanol consumption and found to be effective in most reports. In clinical use, naltrexone has not proved to be as efficacious in preventing relapse. While naltrexone targets opioid receptors, many other neurotransmitter systems are targeted by ethanol and, to a greater or lesser extent, contribute to modulating ethanol's reinforcing effects. There has been indication that drugs active at the gamma amino butyric acid B (GABAB) receptors can affect the self-administration of many drugs with abuse potential. The experiments reported here evaluated the effect of three doses of baclofen (2.5, 5.0, or 7.5 mg/kg), a GABAB agonist, administered alone or in combination with a single dose of naltrexone (1.0 mg/kg). In Experiment 1, both naltrexone and baclofen, at the two higher doses tested, significantly reduced ethanol consumption in Wistar rats using a limited access procedure on Drug Days 1 and 2. When combined on Drug Days 3 and 4, baclofen/naltrexone was significantly more effective in reducing ethanol consumption than did either drug alone. Neither drug, alone or in combination, had an effect on water consumption. In Experiment 2, both baclofen and naltrexone again significantly reduced ethanol consumption, with no evidence that chronic administration across Drug Days 3 and 4 further reduced consumption compared with Drug Days 1 and 2. The clinical use of multiple pharmacotherapeutic agents in combination may allow for the use of lower doses of individual components, thereby reducing the negative side effects that contribute to lower compliance and higher relapse.
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Affiliation(s)
- Michael F Stromberg
- Center For Studies of Addiction, Department of Psychiatry, University of Pennsylvania, Philadelphia, PA 19104, USA.
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43
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Khaimova E, Kandov Y, Israel Y, Cataldo G, Hadjimarkou MM, Bodnar RJ. Opioid receptor subtype antagonists differentially alter GABA agonist-induced feeding elicited from either the nucleus accumbens shell or ventral tegmental area regions in rats. Brain Res 2005; 1026:284-94. [PMID: 15488491 DOI: 10.1016/j.brainres.2004.08.032] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/15/2004] [Indexed: 11/30/2022]
Abstract
Food intake is significantly increased by administration of either GABAA (e.g., muscimol) or GABAB (e.g., baclofen) agonists into either the shell region of the nucleus accumbens (NAC) or the ventral tegmental area (VTA); these responses are selectively blocked by pretreatment with corresponding GABAA and GABAB antagonists. Previous studies found that a single dose (5 microg) of the general opioid antagonist, naltrexone reduced feeding elicited by muscimol, but not baclofen in the NAC shell, and reduced feeding elicited by baclofen, but not muscimol in the VTA. The present study compared feeding responses elicited by either muscimol or baclofen in either the VTA and NAC shell following pretreatment with equimolar doses of selective mu (0.4, 4 microg), delta (0.4, 4 microg), or kappa (0.6, 6 microg) opioid receptor subtype antagonists. Muscimol (25 ng) and baclofen (200 microg) each significantly and equi-effectively increased food intake over 4 h following VTA or NAC shell microinjections. Muscimol-induced feeding elicited from the VTA was significantly enhanced by mu or delta antagonists, and was significantly reduced by kappa antagonists. Baclofen-induced feeding elicited from the VTA was significantly reduced by mu or kappa, but not delta antagonists. Muscimol-induced feeding elicited from the NAC was significantly reduced by either mu, kappa or delta antagonists. Baclofen-induced feeding elicited from the NAC was significantly reduced by kappa or delta, but not mu antagonists. These data indicate differential opioid receptor subtype antagonist-induced mediation of GABA receptor subtype agonist-induced feeding elicited from the VTA and NAC shell. This is consistent with previously demonstrated differential GABA receptor subtype antagonist-induced mediation of opioid-induced feeding elicited from these same sites. Thus, functional relationships exist for the elaborate anatomical and physiological interactions between these two neurochemical systems in the VTA and NAC shell.
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Affiliation(s)
- Eleonora Khaimova
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, 65-30 Kissena Boulevard, Flushing, NY 11367, USA
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Melis M, Spiga S, Diana M. The dopamine hypothesis of drug addiction: hypodopaminergic state. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2005; 63:101-54. [PMID: 15797467 DOI: 10.1016/s0074-7742(05)63005-x] [Citation(s) in RCA: 188] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Miriam Melis
- B.B. Brodie Department of Neuroscience, University of Cagliari, 09042 Monserrato, Italy
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45
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Adell A, Artigas F. The somatodendritic release of dopamine in the ventral tegmental area and its regulation by afferent transmitter systems. Neurosci Biobehav Rev 2004; 28:415-31. [PMID: 15289006 DOI: 10.1016/j.neubiorev.2004.05.001] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2004] [Revised: 05/12/2004] [Accepted: 05/12/2004] [Indexed: 10/26/2022]
Abstract
The release of dopamine in the ventral tegmental area (VTA) plays an important role in the autoinhibition of the dopamine neurons of the mesocorticolimbic system through the activation of somatodendritic dopamine D2 autoreceptors. Accordingly, the intra-VTA application of dopamine D2 receptor agonists reduces the firing rate and release of dopamine in the VTA, and this control appears to possess a tonic nature because the corresponding antagonists enhance the somatodendritic release of the transmitter. In addition, the release of dopamine in the VTA is increased by potassium or veratridine depolarization and abolished by tetrodotoxin and calcium omission. Overall, it appears that the somatodendritic release of dopamine is consistently lower than that in nerve endings. Apart from intrinsic dopaminergic mechanisms, other transmitter systems such as serotonin, noradrenaline, acetylcholine, GABA and glutamate play a role in the control of the activity of dopaminergic neurons of the VTA, although the final action depends on the particular receptor involved as well as the neuronal type where it is localized. Given the involvement of the mesocorticolimbic dopaminergic systems in the pathogenesis of severe neuropsychiatric disorders such as schizophrenia, the knowledge of the factors that regulate the release of dopamine in the VTA could provide new insight into the ethiogenesis of the disease as well as its implication on the mechanisms of action of therapeutic drugs.
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Affiliation(s)
- Albert Adell
- Department of Neurochemistry, Institut d'Investigacions Biomèdiques de Barcelona, CSIC (IDIBAPS), Carrer Rosselló 161, 6th floor, E-08036 Barcelona, Spain.
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46
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Lile JA, Stoops WW, Glaser PEA, Hays LR, Rush CR. Acute administration of the GABA reuptake inhibitor tiagabine does not alter the effects of oral cocaine in humans. Drug Alcohol Depend 2004; 76:81-91. [PMID: 15380292 DOI: 10.1016/j.drugalcdep.2004.04.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2003] [Revised: 04/05/2004] [Accepted: 04/20/2004] [Indexed: 11/19/2022]
Abstract
Drugs affecting central gamma-aminobutyric acid (GABA) systems may have promise as treatments for cocaine addiction. In the present study, tiagabine (Gabatril), a GABA reuptake inhibitor, was investigated for its ability to modify the discriminative-stimulus, reinforcing, subject-rated, performance and cardiovascular effects of oral cocaine in non-treatment seeking cocaine users. Initially, acute doses of 4 mg tiagabine were tested alone and in combination with oral cocaine in four participants to establish the safety of cocaine-tiagabine combinations. A higher dose of tiagabine (8 mg) was then tested in a larger group (n = 6). Participants learned to discriminate 150 mg of oral cocaine. The effects of cocaine (0-150 mg, p.o.) administered alone and in combination with tiagabine were then determined. Subject-rated, performance and cardiovascular measures were obtained at regular intervals. The reinforcing effects of cocaine, tiagabine and cocaine-tiagabine combinations were assessed using the Multiple-Choice Procedure. Cocaine alone produced prototypical behavioral and physiological effects (i.e., functioned as a discriminative and reinforcing stimulus, produced stimulant-like subject-rated effects, improved performance and increased heart rate). In general, acute administration of tiagabine did not alter the effects of oral cocaine. These findings suggest that tiagabine would not be effective at preventing continued cocaine use by blocking its acute, abuse-related effects.
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Affiliation(s)
- Joshua A Lile
- Department of Behavioral Science, College of Medicine, University of Kentucky, College of Medicine Office Building (Room No. 127), Lexington, KY 40536-0086, USA
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47
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Bartoletti M, Gubellini C, Ricci F, Gaiardi M. The GABAB agonist baclofen blocks the expression of sensitisation to the locomotor stimulant effect of amphetamine. Behav Pharmacol 2004; 15:397-401. [PMID: 15343066 DOI: 10.1097/00008877-200409000-00014] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The purpose of the present study was to test the possible influence of baclofen, a GABAB agonist, on the long-term sensitisation to amphetamine in rats. As expected, chronic amphetamine treatment (1.5 mg/kg i.p. daily for 10 days) led to an increased locomotor response to amphetamine (0.75 mg/kg i.p.), when the animals were challenged 20 days after the end of repeated treatment. Baclofen (2 mg/kg i.p.), administered before the test session, did not significantly modify the spontaneous locomotor activity of rats, but decreased the normal and, to a greater extent, the sensitised locomotor response to amphetamine; thus baclofen prevented the expression of sensitisation to amphetamine. Moreover a previous chronic treatment with baclofen (2 mg/kg i.p. daily for 10 days) attenuated the amphetamine-induced locomotor activity in sensitised, but not in control animals. This effect was observed 20 days after the last baclofen administration. In conclusion, the present results demonstrate that GABAB receptors play an important role in the expression of the sensitised behavioural response to amphetamine and further support a potential role of GABAB agonists in the treatment of psychostimulant addiction.
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Affiliation(s)
- M Bartoletti
- Department of Pharmacology, University of Bologna, Via Irnerio 48, I-40126 Bologna, Italy.
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48
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Rush CR, Stoops WW, Wagner FP, Hays LR, Glaser PEA. Alprazolam attenuates the behavioral effects of d-amphetamine in humans. J Clin Psychopharmacol 2004; 24:410-20. [PMID: 15232333 DOI: 10.1097/01.jcp.0000130553.55630.ad] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The results of preclinical behavioral pharmacology studies suggest that gamma-aminobutyric acidA (GABAA) receptor modulators attenuate the behavioral effects of commonly abused stimulants such as amphetamines and cocaine under a variety of behavioral arrangements including drug discrimination and self-administration. In the present experiment, 6 healthy humans learned to discriminate 15-mg oral D-amphetamine. After acquiring the discrimination (ie, . > or = 80% correct responding on 4 consecutive days), the effects of a range of doses of D-amphetamine (0, 2.5, 5, 10, and 15 mg), alone and following pretreatment with alprazolam (0 and 0.5 mg), a GABAA receptor modulator, were assessed. D-Amphetamine alone functioned as a discriminative stimulus and produced stimulant-like self-reported drug effects (eg, increased scores on a Stimulant-Sensitive Adjective-Rating Scale). These effects were generally a function of dose. Alprazolam alone did not occasion D-amphetamine-like discriminative stimulus effects, nor did it increase ratings of sedation or impair performance. Alprazolam pretreatment significantly attenuated the discriminative stimulus effects of D-amphetamine, and some of the self-reported drug effects. Future human laboratory experiments should compare the behavioral effects of D-amphetamine alone and following pretreatment with alprazolam using other behavioral arrangements such as drug self-administration. Future laboratory experiments with humans should also determine if benzodiazepines with lower abuse potential (eg, oxazepam) might also attenuate the behavioral effects of D-amphetamine.
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Affiliation(s)
- Craig R Rush
- Department of Behavioral Science, College of Medicine, University of Kentucky, Lexington, KY 40536-0086, USA.
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49
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Laviolette SR, Gallegos RA, Henriksen SJ, van der Kooy D. Opiate state controls bi-directional reward signaling via GABAA receptors in the ventral tegmental area. Nat Neurosci 2004; 7:160-9. [PMID: 14730310 DOI: 10.1038/nn1182] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2003] [Accepted: 12/23/2003] [Indexed: 11/09/2022]
Abstract
The neural mechanisms that mediate the transition from a drug-naive state to a state of drug dependence and addiction are not yet known. Here we show that a discrete population of GABA(A) receptors in the mammalian ventral tegmental area (VTA) serves as a potential addiction switching mechanism by gating reward transmission through one of two neural motivational systems: either a dopamine-independent (opiate-naive) or a dopaminergic (opiate-dependent or opiate-withdrawn) system. Bi-directional transmission of reward signals through this GABA(A) receptor substrate is dynamically controlled by the opiate state of the organism and involves a molecular alteration of the GABA(A) receptor. After opiate exposure and subsequent withdrawal, the functional conductance properties of the rat VTA GABA(A) receptor switch from an inhibitory to an excitatory signaling mode.
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Affiliation(s)
- Steven R Laviolette
- Neurobiology Research Group, Department of Anatomy and Cell Biology, University of Toronto, Ontario M5S 1A8, Canada.
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50
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Ackerman TF, Lamonte N, Bodnar RJ. Lack of intersite GABA receptor subtype antagonist effects upon mu opioid receptor agonist-induced feeding elicited from either the ventral tegmental area or nucleus accumbens shell in rats. Physiol Behav 2003; 79:191-8. [PMID: 12834790 DOI: 10.1016/s0031-9384(03)00087-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Pretreatment with the GABA(A) receptor antagonist, bicuculline or the GABA(B) receptor antagonist, saclofen, into the nucleus accumbens (Nacc) shell, respectively, potentiates and reduces feeding elicited by the mu opioid agonist, [D-Ala(2), Nme(4), Gly-ol(5)]-enkephalin (DAMGO), administered into the same site. DAMGO-induced feeding elicited from the ventral tegmental area (VTA) region is significantly reduced by pretreatment with saclofen into the same site indicating local GABA mediation of opioid-induced feeding in each site. Given the neuroanatomical and functional connections between the two sites, the present study evaluated the dose-dependent actions of bicuculline and saclofen pretreatment in one site upon DAMGO-induced feeding elicited from the second site. Pretreatment of either bicuculline (7.5-75 ng) or saclofen (1.5-10 microg) into the Nacc shell failed to alter the time course or magnitude of DAMGO-induced feeding elicited from the VTA region. DAMGO-induced feeding elicited from the Nacc shell was unaffected by VTA region pretreatment with either bicuculline (7.5-75 ng) or saclofen (1.5-5 microg). A higher (10 microg) saclofen dose prevented significant DAMGO-induced feeding after 1 and 4 h. Thus, although GABA receptor subtype antagonists are capable of differentially modulating DAMGO-induced feeding when both drugs are applied locally in either the VTA region or the Nacc shell, it appears that any effects between the VTA region and the Nacc shell in modulating DAMGO-induced feeding do not depend upon a GABAergic synapse in the other site.
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Affiliation(s)
- Tsippa F Ackerman
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, 65-30 Kissena Boulevard, Flushing, NY 11367, USA
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