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The Role of Nuclear Hormone Receptors in Cannabinoid Function. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2017; 80:291-328. [PMID: 28826538 DOI: 10.1016/bs.apha.2017.03.008] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Since the early 2000s, evidence has been accumulating that most cannabinoid compounds interact with the nuclear hormone family peroxisome proliferator-activated receptors (PPARs). This can be through direct binding of these compounds to PPARs, metabolism of cannabinoid to other PPAR-activating chemicals, or indirect activation of PPAR through cell signaling pathways. Delivery of cannabinoids to the nucleus may be facilitated by fatty acid-binding proteins and carrier proteins. All PPAR isoforms appear to be activated by cannabinoids, but the majority of evidence is for PPARα and γ. To date, little is known about the potential interaction of cannabinoids with other nuclear hormones. At least some (but not all) of the well-known biological actions of cannabinoids including neuroprotection, antiinflammatory action, and analgesic effects are partly mediated by PPAR-activation, often in combination with activation of the more traditional target sites of action. This has been best investigated for the endocannabinoid-like compounds palmitoylethanolamide and oleoylethanolamine acting at PPARα, and for phytocannabinoids or their derivatives activation acting at PPARγ. However, there are still many aspects of cannabinoid activation of PPAR and the role it plays in the biological and therapeutic effects of cannabinoids that remain to be investigated.
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Scheggi S, Ferrari A, Pelliccia T, Devoto P, De Montis MG, Gambarana C. Fasting biases μ-opioid receptors toward β-arrestin2-dependent signaling in the accumbens shell. Neuroscience 2017; 352:19-29. [PMID: 28391016 DOI: 10.1016/j.neuroscience.2017.03.056] [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] [Received: 10/31/2016] [Revised: 03/03/2017] [Accepted: 03/28/2017] [Indexed: 10/19/2022]
Abstract
The μ-opioid receptor (MOR) and dopamine D1 receptor are co-expressed in the medium spiny neurons of striatal areas and the signaling pathways activated by these two receptors are in functional competition. However, in certain conditions an integrated response mediated by the dopamine D1 receptor transduction system is observed. In mice, morphine administration induces hypermotility and this response has been described in terms of a β-arrestin2-dependent mechanism that favors prevalent dopamine D1 receptor activation. In rats, acute morphine administration induces hypermotility only when the animals are food-deprived (FD). We aimed to further investigate the functional interaction between the MOR and dopamine D1 receptors in striatal areas and we studied the effects of acute pharmacological MOR stimulation on motility and nucleus accumbens shell (NAcS) dopamine D1 receptor signaling in control rats and rats with reduced β-arrestin2 expression in the NAcS, either non food-deprived (NFD) or FD. Motility and dopamine D1 receptor signaling increased only in FD rats in a β-arrestin2-dependent way. Moreover, FD rats showed a β-arrestin2-dependent increase in the levels of MOR-dopamine D1 receptor heteromeric complexes in the NAcS. Sucrose consumption is accompanied by release of endogenous opioids and dopamine in the NAcS. We then examined MOR-dopamine D1 receptor interactions after sucrose consumption. Sucrose increased NAcS dopamine D1 receptor signaling in NFD and FD rats, and a reduction in β-arrestin2 expression prevented this effect selectively in FD rats. These results show the β-arrestin2-dependent prevalence of dopamine D1 receptor signaling in response to acute morphine or sucrose consumption elicited by food deprivation in rats.
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Affiliation(s)
- Simona Scheggi
- Department of Molecular and Developmental Medicine, University of Siena, Siena, Italy
| | - Alberto Ferrari
- Department of Molecular and Developmental Medicine, University of Siena, Siena, Italy
| | - Teresa Pelliccia
- Department of Molecular and Developmental Medicine, University of Siena, Siena, Italy
| | - Paola Devoto
- Department of Biomedical Sciences, University of Cagliari, Italy
| | | | - Carla Gambarana
- Department of Molecular and Developmental Medicine, University of Siena, Siena, Italy.
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In vivo interactions between α7 nicotinic acetylcholine receptor and nuclear peroxisome proliferator-activated receptor-α: Implication for nicotine dependence. Neuropharmacology 2017; 118:38-45. [PMID: 28279662 DOI: 10.1016/j.neuropharm.2017.03.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Revised: 02/27/2017] [Accepted: 03/04/2017] [Indexed: 12/21/2022]
Abstract
Chronic tobacco use dramatically increases health burdens and financial costs. Limitations of current smoking cessation therapies indicate the need for improved molecular targets. The main addictive component of tobacco, nicotine, exerts its dependency effects via nicotinic acetylcholine receptors (nAChRs). Activation of the homomeric α7 nAChR reduces nicotine's rewarding properties in conditioned place preference (CPP) test and i.v. self-administration models, but the mechanism underlying these effects is unknown. Recently, the nuclear receptor peroxisome proliferator-activated receptor type-α (PPARα) has been implicated as a downstream signaling target of the α7 nAChR in ventral tegmental area dopamine cells. The present study investigated PPARα as a possible mediator of the effect of α7 nAChR activation in nicotine dependence. Our results demonstrate the PPARα antagonist GW6471 blocks actions of the α7 nAChR agonist PNU282987 on nicotine reward in an unbiased CPP test in male ICR adult mice. These findings suggests that α7 nAChR activation attenuates nicotine CPP in a PPARα-dependent manner. To evaluate PPARα activation in nicotine dependence we used the selective and potent PPARα agonist, WY-14643 and the clinically used PPARα activator, fenofibrate, in nicotine CPP and we observed attenuation of nicotine preference, but fenofibrate was less potent. We also studied PPARα in nicotine dependence by evaluating its activation in nicotine withdrawal. WY-14643 reversed nicotine withdrawal signs whereas fenofibrate had modest efficacy. This suggests that PPARα plays a role in nicotine reward and withdrawal and that further studies are warranted to elucidate its function in mediating the effects of α7 nAChRs in nicotine dependence.
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The Epac-Phospholipase Cε Pathway Regulates Endocannabinoid Signaling and Cocaine-Induced Disinhibition of Ventral Tegmental Area Dopamine Neurons. J Neurosci 2017; 37:3030-3044. [PMID: 28209735 DOI: 10.1523/jneurosci.2810-16.2017] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2016] [Revised: 01/26/2017] [Accepted: 02/06/2017] [Indexed: 11/21/2022] Open
Abstract
Exchange protein directly activated by cAMP (Epac) is a direct effector for the ubiquitous second messenger cAMP. Epac activates the phospholipase Cε (PLCε) pathway. PLCβ has been linked to the synthesis of the endocannabinoid 2-arachidonoylglycerol (2-AG). Here, we report that Epac facilitates endocannabinoid-mediated retrograde synaptic depression through activation of PLCε. Intracellular loading of a selective Epac agonist 8-CPT-2Me-cAMP into ventral tegmental area (VTA) dopamine neurons enabled previously ineffective stimuli to induce depolarization-induced suppression of inhibition (DSI) and long-term depression of IPSCs (I-LTD) in the VTA. DSI and I-LTD are mediated by 2-AG since they were blocked by a diacylglycerol lipase inhibitor. The effects of 8-CPT-2Me-cAMP on DSI and I-LTD were absent in Epac2 and PLCε knock-out mice, but remained intact in Epac1 knock-out mice. These results identify a novel mechanism for on-demand synthesis of retrograde signaling 2-AG by the Epac2-PLCε pathway. We investigated the functional significance of Epac2-PLCε-2-AG signaling in regulating inhibitory synaptic plasticity in VTA dopamine neurons induced by in vivo cocaine exposure. We showed that cocaine place conditioning led to a decrease in the frequency and amplitude of spontaneous IPSCs and an increase in action potential firing in wild-type mice, but not in Epac2 or PLCε knock-out mice. Together, these results indicate that the Epac2-PLCε-2-AG signaling cascade contributes to cocaine-induced disinhibition of VTA dopamine neurons.SIGNIFICANCE STATEMENT 2-arachidonoylglycerol (2-AG) is an endogenous cannabinoid that depresses synaptic transmission through stimulation of CB1 receptors. Among the six isoforms of phospholipase C (PLC; PLCβ, PLCγ, PLCδ, PLCε, PLCζ, PLCη), only PLCβ has been linked to 2-AG synthesis. Here we demonstrate that 8-CPT-2Me-cAMP, a selective agonist of the cAMP sensor protein Epac, enhances 2-AG-mediated synaptic depression in ventral tegmental area (VTA) dopamine neurons via activation of PLCε. These results identify a novel mechanism for 2-AG synthesis via activation of the Epac-PLCε pathway. Furthermore, we show that cocaine-induced conditioned place preference and disinhibition of VTA dopamine neurons were impaired in mice lacking Epac or PLCε. Thus, the Epac-PLCε signaling pathway contributes to cocaine-induced disinhibition of VTA dopamine neurons and formation of drug-associated memories.
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Haile CN, Kosten TA. The peroxisome proliferator-activated receptor alpha agonist fenofibrate attenuates alcohol self-administration in rats. Neuropharmacology 2017; 116:364-370. [PMID: 28088358 DOI: 10.1016/j.neuropharm.2017.01.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Revised: 01/05/2017] [Accepted: 01/10/2017] [Indexed: 10/20/2022]
Abstract
Fibrates are a class of medications used to treat hypercholesterolemia and dyslipidemia that target nuclear peroxisome proliferator-activated receptors (PPARs). Studies have shown the PPARα agonist fenofibrate decreases voluntary EtOH consumption however its impact on the reinforcing and motivational effects of EtOH is unknown. We evaluated the ability of fenofibrate (25, 50 and 100 mg/kg), to alter EtOH (10%, w/v) and sucrose (2%, w/v) operant self-administration in rats under a FR2 schedule of reinforcement over four days and under a progressive ratio (PR) schedule on day five of treatment. Results showed fenofibrate dose-dependently decreased EtOH self-administration under both schedules of reinforcement with the greatest effects seen after four to five days of treatment. Fenofibrate decreased responding for sucrose only under the PR schedule of reinforcement and this effect was not dose-dependent. These findings provide further evidence for fenofibrate as a potential treatment for alcohol use disorder in humans.
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Affiliation(s)
- Colin N Haile
- University of Houston, Department of Psychology, Houston, TX 77204-6022, United States; Texas Institute for Measurement, Evaluation and Statistics (TIMES), Houston, TX 77204-6022, United States.
| | - Therese A Kosten
- University of Houston, Department of Psychology, Houston, TX 77204-6022, United States; Texas Institute for Measurement, Evaluation and Statistics (TIMES), Houston, TX 77204-6022, United States
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Scheggi S, Melis M, De Felice M, Aroni S, Muntoni AL, Pelliccia T, Gambarana C, De Montis MG, Pistis M. PPARα modulation of mesolimbic dopamine transmission rescues depression-related behaviors. Neuropharmacology 2016; 110:251-259. [PMID: 27457507 DOI: 10.1016/j.neuropharm.2016.07.024] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 06/19/2016] [Accepted: 07/20/2016] [Indexed: 01/08/2023]
Abstract
Depressive disorders cause a substantial burden for the individual and the society. Key depressive symptoms can be modeled in animals and enable the development of novel therapeutic interventions. Chronic unavoidable stress disrupts rats' competence to escape noxious stimuli and self-administer sucrose, configuring a depression model characterized by escape deficit and motivational anhedonia associated to impaired dopaminergic responses to sucrose in the nucleus accumbens shell (NAcS). Repeated treatments that restore these responses also relieve behavioral symptoms. Ventral tegmental area (VTA) dopamine neurons encode reward and motivation and are implicated in the neuropathology of depressive-like behaviors. Peroxisome proliferator-activated receptors type-α (PPARα) acutely regulate VTA dopamine neuron firing via β2 subunit-containing nicotinic acetylcholine receptors (β2*nAChRs) through phosphorylation and this effect is predictive of antidepressant-like effects. Here, by combining behavioral, electrophysiological and biochemical techniques, we studied the effects of repeated PPARα stimulation by fenofibrate on mesolimbic dopamine system. We found decreased β2*nAChRs phosphorylation levels and a switch from tonic to phasic activity of dopamine cells in the VTA, and increased phosphorylation of dopamine and cAMP-regulated phosphoprotein Mr 32,000 (DARPP-32) in the NAcS. We then investigated whether long-term fenofibrate administration to stressed rats reinstated the decreased DARPP-32 response to sucrose and whether this effect translated into antidepressant-like properties. Fenofibrate restored dopaminergic responses to appetitive stimuli, reactivity to aversive stimuli and motivation to self-administer sucrose. Overall, this study suggests PPARα as new targets for antidepressant therapies endowed with motivational anti-anhedonic properties, further supporting the role of an unbalanced mesolimbic dopamine system in pathophysiology of depressive disorders.
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Affiliation(s)
- Simona Scheggi
- Department of Molecular and Developmental Medicine, University of Siena, 53100 Siena, Italy
| | - Miriam Melis
- Division of Neuroscience and Clinical Pharmacology, Department of Biomedical Sciences, University of Cagliari, 09042 Monserrato, Italy
| | - Marta De Felice
- Division of Neuroscience and Clinical Pharmacology, Department of Biomedical Sciences, University of Cagliari, 09042 Monserrato, Italy
| | - Sonia Aroni
- Division of Neuroscience and Clinical Pharmacology, Department of Biomedical Sciences, University of Cagliari, 09042 Monserrato, Italy
| | - Anna Lisa Muntoni
- Neuroscience Institute, National Research Council of Italy, Section of Cagliari, Italy
| | - Teresa Pelliccia
- Department of Molecular and Developmental Medicine, University of Siena, 53100 Siena, Italy
| | - Carla Gambarana
- Department of Molecular and Developmental Medicine, University of Siena, 53100 Siena, Italy
| | | | - Marco Pistis
- Division of Neuroscience and Clinical Pharmacology, Department of Biomedical Sciences, University of Cagliari, 09042 Monserrato, Italy; Neuroscience Institute, National Research Council of Italy, Section of Cagliari, Italy.
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Grasing K. A threshold model for opposing actions of acetylcholine on reward behavior: Molecular mechanisms and implications for treatment of substance abuse disorders. Behav Brain Res 2016; 312:148-62. [PMID: 27316344 DOI: 10.1016/j.bbr.2016.06.022] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 06/11/2016] [Accepted: 06/13/2016] [Indexed: 12/26/2022]
Abstract
The cholinergic system plays important roles in both learning and addiction. Medications that modify cholinergic tone can have pronounced effects on behaviors reinforced by natural and drug reinforcers. Importantly, enhancing the action of acetylcholine (ACh) in the nucleus accumbens and ventral tegmental area (VTA) dopamine system can either augment or diminish these behaviors. A threshold model is presented that can explain these seemingly contradictory results. Relatively low levels of ACh rise above a lower threshold, facilitating behaviors supported by drugs or natural reinforcers. Further increases in cholinergic tone that rise above a second upper threshold oppose the same behaviors. Accordingly, cholinesterase inhibitors, or agonists for nicotinic or muscarinic receptors, each have the potential to produce biphasic effects on reward behaviors. Pretreatment with either nicotinic or muscarinic antagonists can block drug- or food- reinforced behavior by maintaining cholinergic tone below its lower threshold. Potential threshold mediators include desensitization of nicotinic receptors and biphasic effects of ACh on the firing of medium spiny neurons. Nicotinic receptors with high- and low- affinity appear to play greater roles in reward enhancement and inhibition, respectively. Cholinergic inhibition of natural and drug rewards may serve as mediators of previously described opponent processes. Future studies should evaluate cholinergic agents across a broader range of doses, and include a variety of reinforced behaviors.
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Affiliation(s)
- Kenneth Grasing
- From the Substance Abuse Research Laboratory, 151, Kansas City Veterans Affairs Medical Center, 4801 Linwood Boulevard, Kansas City, MO 64128, United States; From the Division of Clinical Pharmacology, Department of Medicine, University of Kansas School of Medicine, Kansas City, KS 66160, United States.
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Scherma M, Muntoni AL, Melis M, Fattore L, Fadda P, Fratta W, Pistis M. Interactions between the endocannabinoid and nicotinic cholinergic systems: preclinical evidence and therapeutic perspectives. Psychopharmacology (Berl) 2016; 233:1765-77. [PMID: 26728894 DOI: 10.1007/s00213-015-4196-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Accepted: 12/13/2015] [Indexed: 12/29/2022]
Abstract
RATIONALE Several lines of evidence suggest that endocannabinoid and nicotinic cholinergic systems are implicated in the regulation of different physiological processes, including reward, and in the neuropathological mechanisms of psychiatric diseases, such as addiction. A crosstalk between these two systems is substantiated by the overlapping distribution of cannabinoid and nicotinic acetylcholine receptors in many brain structures. OBJECTIVE We will review recent preclinical data showing how the endocannabinoid and nicotinic cholinergic systems interact bidirectionally at the level of the brain reward pathways, and how this interaction plays a key role in modulating nicotine and cannabinoid intake and dependence. RESULTS Many behavioral and neurochemical effects of nicotine that are related to its addictive potential are reduced by pharmacological blockade or genetic deletion of type-1 cannabinoid receptors, inhibition of endocannabinoid uptake or metabolic degradation, and activation of peroxisome proliferator-activated-receptor-α. On the other hand, cholinergic antagonists at α7 nicotinic acetylcholine receptors as well as endogenous negative allosteric modulators of these receptors are effective in blocking dependence-related effects of cannabinoids. CONCLUSIONS Pharmacological manipulation of the endocannabinoid system and endocannabinoid-like neuromodulators shows promise in the treatment of nicotine dependence and in relapse prevention. Likewise, drugs acting at nicotinic acetylcholine receptors might prove useful in the therapy of cannabinoid dependence. Research by Steven R. Goldberg has significantly contributed to the progress in this research field.
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Affiliation(s)
- Maria Scherma
- Department of Biomedical Sciences, Division of Neuroscience and Clinical Pharmacology, University of Cagliari, Cittadella Universitaria, Monserrato (CA), 09042, Italy
| | - Anna Lisa Muntoni
- Neuroscience Institute, section of Cagliari, National Research Council, Cagliari, Italy
- Centre of Excellence "Neurobiology of Dependence", University of Cagliari, Cagliari, Italy
| | - Miriam Melis
- Department of Biomedical Sciences, Division of Neuroscience and Clinical Pharmacology, University of Cagliari, Cittadella Universitaria, Monserrato (CA), 09042, Italy
| | - Liana Fattore
- Neuroscience Institute, section of Cagliari, National Research Council, Cagliari, Italy
- Centre of Excellence "Neurobiology of Dependence", University of Cagliari, Cagliari, Italy
| | - Paola Fadda
- Department of Biomedical Sciences, Division of Neuroscience and Clinical Pharmacology, University of Cagliari, Cittadella Universitaria, Monserrato (CA), 09042, Italy
- Centre of Excellence "Neurobiology of Dependence", University of Cagliari, Cagliari, Italy
| | - Walter Fratta
- Department of Biomedical Sciences, Division of Neuroscience and Clinical Pharmacology, University of Cagliari, Cittadella Universitaria, Monserrato (CA), 09042, Italy
- Centre of Excellence "Neurobiology of Dependence", University of Cagliari, Cagliari, Italy
| | - Marco Pistis
- Department of Biomedical Sciences, Division of Neuroscience and Clinical Pharmacology, University of Cagliari, Cittadella Universitaria, Monserrato (CA), 09042, Italy.
- Neuroscience Institute, section of Cagliari, National Research Council, Cagliari, Italy.
- Centre of Excellence "Neurobiology of Dependence", University of Cagliari, Cagliari, Italy.
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Moreno S, Cerù MP. In search for novel strategies towards neuroprotection and neuroregeneration: is PPARα a promising therapeutic target? Neural Regen Res 2015; 10:1409-12. [PMID: 26604898 PMCID: PMC4625503 DOI: 10.4103/1673-5374.165313] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Sandra Moreno
- Department of Science-LIME, University Roma Tre, Rome, Italy
| | - Maria Paola Cerù
- Department of Science-LIME, University Roma Tre, Rome, Italy ; Department of Life, Health and Environmental Sciences, University of L'Aquila, Coppito (AQ), Italy
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60
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Justinova Z, Panlilio LV, Moreno-Sanz G, Redhi GH, Auber A, Secci ME, Mascia P, Bandiera T, Armirotti A, Bertorelli R, Chefer SI, Barnes C, Yasar S, Piomelli D, Goldberg SR. Effects of Fatty Acid Amide Hydrolase (FAAH) Inhibitors in Non-Human Primate Models of Nicotine Reward and Relapse. Neuropsychopharmacology 2015; 40:2185-97. [PMID: 25754762 PMCID: PMC4613608 DOI: 10.1038/npp.2015.62] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 02/20/2015] [Accepted: 02/21/2015] [Indexed: 01/01/2023]
Abstract
Inhibition of the enzyme fatty acid amide hydrolase (FAAH) counteracts reward-related effects of nicotine in rats, but it has not been tested for this purpose in non-human primates. Therefore, we studied the effects of the first- and second-generation O-arylcarbamate-based FAAH inhibitors, URB597 (cyclohexyl carbamic acid 3'-carbamoyl-3-yl ester) and URB694 (6-hydroxy-[1,1'-biphenyl]-3-yl-cyclohexylcarbamate), in squirrel monkeys. Both FAAH inhibitors: (1) blocked FAAH activity in brain and liver, increasing levels of endogenous ligands for cannabinoid and α-type peroxisome proliferator-activated (PPAR-α) receptors; (2) shifted nicotine self-administration dose-response functions in a manner consistent with reduced nicotine reward; (3) blocked reinstatement of nicotine seeking induced by reexposure to either nicotine priming or nicotine-associated cues; and (4) had no effect on cocaine or food self-administration. The effects of FAAH inhibition on nicotine self-administration and nicotine priming-induced reinstatement were reversed by the PPAR-α antagonist, MK886. Unlike URB597, which was not self-administered by monkeys in an earlier study, URB694 was self-administered at a moderate rate. URB694 self-administration was blocked by pretreatment with an antagonist for either PPAR-α (MK886) or cannabinoid CB1 receptors (rimonabant). In additional experiments in rats, URB694 was devoid of THC-like or nicotine-like interoceptive effects under drug-discrimination procedures, and neither of the FAAH inhibitors induced dopamine release in the nucleus accumbens shell--consistent with their lack of robust reinforcing effects in monkeys. Overall, both URB597 and URB694 show promise for the initialization and maintenance of smoking cessation because of their ability to block the rewarding effects of nicotine and prevent nicotine priming-induced and cue-induced reinstatement.
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Affiliation(s)
- Zuzana Justinova
- Preclinical Pharmacology Section, Behavioral Neuroscience Research Branch, Intramural Research Program, National Institute on Drug Abuse, NIH, DHHS, Baltimore, MD, USA,Preclinical Pharmacology Section, Intramural Research Program, National Institute on Drug Abuse, NIH, DHHS, 251 Bayview Boulevard, Baltimore, MD 21224, USA, Tel: +1 443 740 2522, Fax: +1 443 740 2733, E-mail:
| | - Leigh V Panlilio
- Preclinical Pharmacology Section, Behavioral Neuroscience Research Branch, Intramural Research Program, National Institute on Drug Abuse, NIH, DHHS, Baltimore, MD, USA
| | - Guillermo Moreno-Sanz
- Department of Anatomy and Neurobiology, University of California, Irvine, Irvine, CA, USA
| | - Godfrey H Redhi
- Preclinical Pharmacology Section, Behavioral Neuroscience Research Branch, Intramural Research Program, National Institute on Drug Abuse, NIH, DHHS, Baltimore, MD, USA
| | - Alessia Auber
- Preclinical Pharmacology Section, Behavioral Neuroscience Research Branch, Intramural Research Program, National Institute on Drug Abuse, NIH, DHHS, Baltimore, MD, USA
| | - Maria E Secci
- Preclinical Pharmacology Section, Behavioral Neuroscience Research Branch, Intramural Research Program, National Institute on Drug Abuse, NIH, DHHS, Baltimore, MD, USA
| | - Paola Mascia
- Preclinical Pharmacology Section, Behavioral Neuroscience Research Branch, Intramural Research Program, National Institute on Drug Abuse, NIH, DHHS, Baltimore, MD, USA
| | - Tiziano Bandiera
- Drug Discovery and Development, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Andrea Armirotti
- Drug Discovery and Development, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Rosalia Bertorelli
- Drug Discovery and Development, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Svetlana I Chefer
- Division of Clinical Research, National Institute of Allergy and Infectious Diseases, NIH, DHHS, Frederick, MD, USA
| | - Chanel Barnes
- Preclinical Pharmacology Section, Behavioral Neuroscience Research Branch, Intramural Research Program, National Institute on Drug Abuse, NIH, DHHS, Baltimore, MD, USA
| | - Sevil Yasar
- Department of Medicine, Division of Geriatric Medicine and Gerontology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Daniele Piomelli
- Department of Anatomy and Neurobiology, University of California, Irvine, Irvine, CA, USA,Drug Discovery and Development, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Steven R Goldberg
- Preclinical Pharmacology Section, Behavioral Neuroscience Research Branch, Intramural Research Program, National Institute on Drug Abuse, NIH, DHHS, Baltimore, MD, USA
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de Kloet SF, Mansvelder HD, De Vries TJ. Cholinergic modulation of dopamine pathways through nicotinic acetylcholine receptors. Biochem Pharmacol 2015. [PMID: 26208783 DOI: 10.1016/j.bcp.2015.07.014] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Nicotine addiction is highly prevalent in current society and is often comorbid with other diseases. In the central nervous system, nicotine acts as an agonist for nicotinic acetylcholine receptors (nAChRs) and its effects depend on location and receptor composition. Although nicotinic receptors are found in most brain regions, many studies on addiction have focused on the mesolimbic system and its reported behavioral correlates such as reward processing and reinforcement learning. Profound modulatory cholinergic input from the pedunculopontine and laterodorsal tegmentum to dopaminergic midbrain nuclei as well as local cholinergic interneuron projections to dopamine neuron axons in the striatum may play a major role in the effects of nicotine. Moreover, an indirect mesocorticolimbic feedback loop involving the medial prefrontal cortex may be involved in behavioral characteristics of nicotine addiction. Therefore, this review will highlight current understanding of the effects of nicotine on the function of mesolimbic and mesocortical dopamine projections in the mesocorticolimbic circuit.
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Affiliation(s)
- Sybren F de Kloet
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cogntive Research (CNCR), Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
| | - Huibert D Mansvelder
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cogntive Research (CNCR), Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands.
| | - Taco J De Vries
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cogntive Research (CNCR), Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands; Department of Anatomy and Neurosciences, Neuroscience Campus Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
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62
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Perkins KA, Karelitz JL, Michael VC, Fromuth M, Conklin CA, Chengappa KNR, Hope C, Lerman C. Initial Evaluation of Fenofibrate for Efficacy in Aiding Smoking Abstinence. Nicotine Tob Res 2015; 18:74-8. [PMID: 25895948 DOI: 10.1093/ntr/ntv085] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Accepted: 04/03/2015] [Indexed: 01/14/2023]
Abstract
INTRODUCTION Primate and rodent models show that peroxisome proliferator-activated receptor-alpha (PPAR-α) ligands, including fibrate medications, reduce nicotine reinforcement, reward, and related effects. We tested fenofibrate, the most common U.S. Food and Drug Administration-approved fibrate for lipid control versus placebo for initial evidence of efficacy in smoking cessation using a validated cross-over procedure for early Phase 2 evaluations. METHODS Adult dependent smokers (N = 38) in this 4-week within-subjects study were those already intending to try to quit in the next 2 months. All smoked ad libitum during weeks 1 (baseline) and 3 (washout) and began fenofibrate (160 mg/d; dosing approved for lipid control) or placebo near the end of weeks 1 and 3. Following each 4-day dose run-up, they were then instructed to try to quit for 4 days (Tuesday-Friday) during weeks 2 and 4, with the order of medication conditions counter-balanced and administered double-blind. Abstinence was verified daily in each 4-day quit period by self-report of no smoking in the prior 24 hours and carbon monoxide < 5 ppm. Secondary measures of acute smoking reinforcement and cue reactivity prior to quitting, and smoking reduction when trying to quit, were also assessed. RESULTS No differences between fenofibrate versus placebo were found on days quit (means ± SEM of 1.8±0.3 vs. 1.9±0.3, respectively). Similarly, there were no differences in any of the secondary measures (all P > .20). CONCLUSIONS Although higher dosing or other proliferator-activated receptor-alpha agonists may show efficacy, this study indicates that fenofibrate does not aid ability to stop smoking during a brief practice quit period in dependent smokers high in current quit interest.
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Affiliation(s)
| | | | | | - Margaret Fromuth
- Department of Psychiatry, University of Pittsburgh, Pittsburgh PA
| | | | | | - Chris Hope
- Department of Psychiatry, University of Pittsburgh, Pittsburgh PA
| | - Caryn Lerman
- Department of Psychiatry and Abramson Cancer Center, University of Pennsylvania, Philadelphia PA
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de Guglielmo G, Melis M, De Luca MA, Kallupi M, Li HW, Niswender K, Giordano A, Senzacqua M, Somaini L, Cippitelli A, Gaitanaris G, Demopulos G, Damadzic R, Tapocik J, Heilig M, Ciccocioppo R. PPARγ activation attenuates opioid consumption and modulates mesolimbic dopamine transmission. Neuropsychopharmacology 2015; 40:927-37. [PMID: 25311134 PMCID: PMC4330506 DOI: 10.1038/npp.2014.268] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 09/01/2014] [Accepted: 09/08/2014] [Indexed: 01/11/2023]
Abstract
PPARγ is one of the three isoforms identified for the peroxisome proliferator-activated receptors (PPARs) and is the receptor for the thiazolidinedione class of anti-diabetic medications including pioglitazone. PPARγ has been long studied for its role in adipogenesis and glucose metabolism, but the discovery of the localization in ventral tegmental area (VTA) neurons opens new vistas for a potential role in the regulation of reward processing and motivated behavior in drug addiction. Here, we demonstrate that activation of PPARγ by pioglitazone reduces the motivation for heroin and attenuates its rewarding properties. These effects are associated with a marked reduction of heroin-induced increase in phosphorylation of DARPP-32 protein in the nucleus accumbens (NAc) and with a marked and selective reduction of acute heroin-induced elevation of extracellular dopamine (DA) levels in the NAc shell, as measured by in vivo microdialysis. Through ex vivo electrophysiology in acute midbrain slices, we also show that stimulation of PPARγ attenuates opioid-induced excitation of VTA DA neurons via reduction of presynaptic GABA release from the rostromedial tegmental nucleus (RMTg). Consistent with this finding, site-specific microinjection of pioglitazone into the RMTg but not into the VTA reduced heroin taking. Our data illustrate that activation of PPARγ may represent a new pharmacotherapeutic option for the treatment of opioid addiction.
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Affiliation(s)
| | - Miriam Melis
- Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy
| | - Maria Antonietta De Luca
- Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy
- INN, National Institute of Neuroscience, Cagliari, Italy
| | - Marsida Kallupi
- School of Pharmacy, Pharmacology Unit, University of Camerino, Camerino, Italy
| | - Hong Wu Li
- School of Pharmacy, Pharmacology Unit, University of Camerino, Camerino, Italy
| | - Kevin Niswender
- Tennessee Valley Healthcare System, Nashville, TN, USA
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Antonio Giordano
- Department of Experimental and Clinical Medicine, Section of Neuroscience and Cell Biology, Università Politecnica delle Marche, Ancona, Italy
| | - Martina Senzacqua
- Department of Experimental and Clinical Medicine, Section of Neuroscience and Cell Biology, Università Politecnica delle Marche, Ancona, Italy
| | - Lorenzo Somaini
- Addiction Treatment Centre, Health Local Unit, ASL 12 Biella, Biella, Italy
| | - Andrea Cippitelli
- School of Pharmacy, Pharmacology Unit, University of Camerino, Camerino, Italy
| | | | | | - Ruslan Damadzic
- Laboratory of Clinical and Translational Studies, National Institute of Alcohol Abuse and Alcoholism (NIAAA), National Institutes of Health (NIH), Bethesda, MD, USA
| | - Jenica Tapocik
- Laboratory of Clinical and Translational Studies, National Institute of Alcohol Abuse and Alcoholism (NIAAA), National Institutes of Health (NIH), Bethesda, MD, USA
| | - Markus Heilig
- Laboratory of Clinical and Translational Studies, National Institute of Alcohol Abuse and Alcoholism (NIAAA), National Institutes of Health (NIH), Bethesda, MD, USA
| | - Roberto Ciccocioppo
- School of Pharmacy, Pharmacology Unit, University of Camerino, Camerino, Italy
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Enhanced endocannabinoid-mediated modulation of rostromedial tegmental nucleus drive onto dopamine neurons in Sardinian alcohol-preferring rats. J Neurosci 2014; 34:12716-24. [PMID: 25232109 DOI: 10.1523/jneurosci.1844-14.2014] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The progressive predominance of rewarding effects of addictive drugs over their aversive properties likely contributes to the transition from drug use to drug dependence. By inhibiting the activity of DA neurons in the VTA, GABA projections from the rostromedial tegmental nucleus (RMTg) are well suited to shift the balance between drug-induced reward and aversion. Since cannabinoids suppress RMTg inputs to DA cells and CB1 receptors affect alcohol intake in rodents, we hypothesized that the endocannabinoid system, by modulating this pathway, might contribute to alcohol preference. Here we found that RMTg afferents onto VTA DA neurons express CB1 receptors and display a 2-arachidonoylglycerol (2-AG)-dependent form of short-term plasticity, that is, depolarization-induced suppression of inhibition (DSI). Next, we compared rodents with innate opposite alcohol preference, the Sardinian alcohol-preferring (sP) and alcohol-nonpreferring (sNP) rats. We found that DA cells from alcohol-naive sP rats displayed a decreased probability of GABA release and a larger DSI. This difference was due to the rate of 2-AG degradation. In vivo, we found a reduced RMTg-induced inhibition of putative DA neurons in sP rats that negatively correlated with an increased firing. Finally, alcohol failed to enhance RMTg spontaneous activity and to prolong RMTg-induced silencing of putative DA neurons in sP rats. Our results indicate functional modifications of RMTg projections to DA neurons that might impact the reward/aversion balance of alcohol attributes, which may contribute to the innate preference observed in sP rats and to their elevated alcohol intake.
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65
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Maex R, Grinevich VP, Grinevich V, Budygin E, Bencherif M, Gutkin B. Understanding the role α7 nicotinic receptors play in dopamine efflux in nucleus accumbens. ACS Chem Neurosci 2014; 5:1032-40. [PMID: 25147933 PMCID: PMC4198061 DOI: 10.1021/cn500126t] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
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Neuronal nicotinic acetylcholine
receptors (NNRs) of the α7
subtype have been shown to contribute to the release of dopamine in
the nucleus accumbens. The site of action and the underlying mechanism,
however, are unclear. Here we applied a circuit modeling approach,
supported by electrochemical in vivo recordings, to clarify this issue.
Modeling revealed two potential mechanisms for the drop in accumbal
dopamine efflux evoked by the selective α7 partial agonist TC-7020.
TC-7020 could desensitize α7 NNRs located predominantly on dopamine
neurons or glutamatergic afferents to them or, alternatively, activate
α7 NNRs located on the glutamatergic afferents to GABAergic
interneurons in the ventral tegmental area. Only the model based on
desensitization, however, was able to explain the neutralizing effect
of coapplied PNU-120596, a positive allosteric modulator. According
to our results, the most likely sites of action are the preterminal
α7 NNRs controlling glutamate release from cortical afferents
to the nucleus accumbens. These findings offer a rationale for the
further investigation of α7 NNR agonists as therapy for diseases
associated with enhanced mesolimbic dopaminergic tone, such as schizophrenia
and addiction.
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Affiliation(s)
- Reinoud Maex
- Department
of Cognitive Sciences, École Normale Supérieure, Paris 75005, France
| | - Vladimir P. Grinevich
- Targacept Inc., Winston-Salem, North Carolina 27101, United States
- Wake Forest School of Medicine, Winston-Salem, North Carolina 27157, United States
| | - Valentina Grinevich
- Wake Forest School of Medicine, Winston-Salem, North Carolina 27157, United States
| | - Evgeny Budygin
- Wake Forest School of Medicine, Winston-Salem, North Carolina 27157, United States
- St. Petersburg State University, St. Petersburg 199034, Russia
| | | | - Boris Gutkin
- Department
of Cognitive Sciences, École Normale Supérieure, Paris 75005, France
- Center
for Cognition and Decision Making, National Research University Higher School of Economics, Moscow 101000, Russia
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66
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Melis M, Pistis M. Targeting the interaction between fatty acid ethanolamides and nicotinic receptors: Therapeutic perspectives. Pharmacol Res 2014; 86:42-9. [DOI: 10.1016/j.phrs.2014.03.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 03/06/2014] [Accepted: 03/24/2014] [Indexed: 12/22/2022]
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Role of nicotinic acetylcholine receptors in regulating dopamine neuron activity. Neuroscience 2014; 282:86-100. [PMID: 24881574 DOI: 10.1016/j.neuroscience.2014.05.040] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 05/20/2014] [Accepted: 05/21/2014] [Indexed: 01/04/2023]
Abstract
Midbrain dopamine (DA) neurons play a central role in a wide range of behaviors, from attention and motivation to motor control and reinforcement. The release of DA is modulated by a number of factors, and its deregulation has been implicated in multiple psychiatric disorders, such as addiction. In particular, nicotinic acetylcholine receptors (nAChRs) are key modulators of DA cells. Nicotine, the main addictive component in tobacco, strongly interacts with these receptors in the midbrain DA systems, resulting in reinforcing effects that are at the core of tobacco addiction. nAChRs are virtually expressed on every cell of the DA system, both at pre-, post- and extra-synaptic locations. The complex issue of interpreting the role of the large portfolio of different nAChR subtypes expressed on ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) neurons, and especially their role in defining functional DAergic subpopulations, is far from being solved. In this review we will try to provide the reader with an integrative view of the nicotinic modulation of DA neurons and its influence at the cellular, systemic and behavioral levels (exploratory behavior), as well as its implication in the reinforcing effects of nicotine.
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68
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Christensen MH, Ishibashi M, Nielsen ML, Leonard CS, Kohlmeier KA. Age-related changes in nicotine response of cholinergic and non-cholinergic laterodorsal tegmental neurons: implications for the heightened adolescent susceptibility to nicotine addiction. Neuropharmacology 2014; 85:263-83. [PMID: 24863041 DOI: 10.1016/j.neuropharm.2014.05.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Revised: 04/30/2014] [Accepted: 05/05/2014] [Indexed: 02/06/2023]
Abstract
The younger an individual starts smoking, the greater the likelihood that addiction to nicotine will develop, suggesting that neurobiological responses vary across age to the addictive component of cigarettes. Cholinergic neurons of the laterodorsal tegmental nucleus (LDT) are importantly involved in the development of addiction, however, the effects of nicotine on LDT neuronal excitability across ontogeny are unknown. Nicotinic effects on LDT cells across different age groups were examined using calcium imaging and whole-cell patch clamping. Within the youngest age group (P7-P15), nicotine induced larger intracellular calcium transients and inward currents. Nicotine induced a greater number of excitatory synaptic currents in the youngest animals, whereas larger amplitude inhibitory synaptic events were induced in cells from the oldest animals (P15-P34). Nicotine increased neuronal firing of cholinergic cells to a greater degree in younger animals, possibly linked to development associated differences found in nicotinic effects on action potential shape and afterhyperpolarization. We conclude that in addition to age-associated alterations of several properties expected to affect resting cell excitability, parameters affecting cell excitability are altered by nicotine differentially across ontogeny. Taken together, our data suggest that nicotine induces a larger excitatory response in cholinergic LDT neurons from the youngest animals, which could result in a greater excitatory output from these cells to target regions involved in development of addiction. Such output would be expected to be promotive of addiction; therefore, ontogenetic differences in nicotine-mediated increases in the excitability of the LDT could contribute to the differential susceptibility to nicotine addiction seen across age.
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Affiliation(s)
- Mark H Christensen
- University of Copenhagen, Department of Drug Design and Pharmacology, Faculty of Health Sciences, Universitetsparken 2, Copenhagen 2100, Denmark
| | - Masaru Ishibashi
- Department of Physiology, New York Medical College, Valhalla, NY 10595, USA
| | - Michael L Nielsen
- University of Copenhagen, Department of Drug Design and Pharmacology, Faculty of Health Sciences, Universitetsparken 2, Copenhagen 2100, Denmark
| | | | - Kristi A Kohlmeier
- University of Copenhagen, Department of Drug Design and Pharmacology, Faculty of Health Sciences, Universitetsparken 2, Copenhagen 2100, Denmark.
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69
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Palmitoylethanolamide in CNS health and disease. Pharmacol Res 2014; 86:32-41. [PMID: 24844438 DOI: 10.1016/j.phrs.2014.05.006] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 05/07/2014] [Accepted: 05/08/2014] [Indexed: 01/08/2023]
Abstract
The existence of acylethanolamides (AEs) in the mammalian brain has been known for decades. Among AEs, palmitoylethanolamide (PEA) is abundant in the central nervous system (CNS) and conspicuously produced by neurons and glial cells. Antihyperalgesic and neuroprotective properties of PEA have been mainly related to the reduction of neuronal firing and to control of inflammation. Growing evidence suggest that PEA may be neuroprotective during CNS neurodegenerative diseases. Advances in the understanding of the physiology and pharmacology of PEA have potentiated its interest as useful biological tool for disease management. Several rapid non-genomic and delayed genomic mechanisms of action have been identified for PEA as peroxisome proliferator-activated receptor (PPAR)-α dependent. First, an early molecular control, through Ca(+2)-activated intermediate- and/or big-conductance K(+) channels opening, drives to rapid neuronal hyperpolarization. This is reinforced by the increase of the inward Cl(-) currents due to the modulation of the gamma aminobutyric acid A receptor and by the desensitization of the transient receptor potential channel type V1. Moreover, the gene transcription-mediated mechanism sustains the long-term anti-inflammatory effects, by reducing pro-inflammatory enzyme expression and increasing neurosteroid synthesis. Overall, the integration of these different modes of action allows PEA to exert an immediate and prolonged efficacious control in neuron signaling either on inflammatory process or neuronal excitability, maintaining cellular homeostasis. In this review, we will discuss the effect of PEA on metabolism, behavior, inflammation and pain perception, related to the control of central functions and the emerging evidence demonstrating its therapeutic efficacy in several neurodegenerative diseases.
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70
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Brunzell DH, McIntosh JM, Papke RL. Diverse strategies targeting α7 homomeric and α6β2* heteromeric nicotinic acetylcholine receptors for smoking cessation. Ann N Y Acad Sci 2014; 1327:27-45. [PMID: 24730978 DOI: 10.1111/nyas.12421] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Preclinical studies suggest that a diversity of nicotinic acetylcholine receptors (nAChRs) with different sensitivities to nicotine may contribute to tobacco addiction. Using rodent intravenous nicotine self-administration as a preclinical model with good predictive validity for therapeutic efficacy for tobacco cessation, investigators have identified heteromeric α6β2* and homomeric α7 nAChRs as promising novel therapeutic targets to promote smoking abstinence (*denotes possible assembly with other subunits). The data suggest that diverse strategies that target these subclasses of nAChRs, namely inhibition of α6β2* nAChRs and stimulation of α7 nAChRs, will support tobacco cessation. α6β2* nAChRs, members of the high-affinity family of β2* nAChRs, function similarly to α4β2* nAChRs, the primary target of the FDA-approved drug varenicline, but have a much more selective neuroanatomical pattern of expression in catecholaminergic nuclei. Although activation of β2* nAChRs facilitates nicotine self-administration, stimulation of α7 nAChRs appears to negatively modulate both nicotine reinforcement and β2* nAChR function in the mesolimbic dopamine system. Although challenges and caveats must be considered in the development of therapeutics that target these nAChR subpopulations, an accumulation of data suggests that α7 nAChR agonists, partial agonists, or positive allosteric modulators and α6β2* nAChR antagonists, partial agonists, or negative allosteric modulators may prove to be effective therapeutics for tobacco cessation.
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Affiliation(s)
- Darlene H Brunzell
- Department of Pharmacology and Toxicology, Interdisciplinary Neuroscience Program and Institute for Drug and Alcohol Studies, Virginia Commonwealth University School of Medicine, Richmond, Virginia
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71
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Hansen HS. Role of anorectic N-acylethanolamines in intestinal physiology and satiety control with respect to dietary fat. Pharmacol Res 2014; 86:18-25. [PMID: 24681513 DOI: 10.1016/j.phrs.2014.03.006] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 03/17/2014] [Accepted: 03/18/2014] [Indexed: 02/06/2023]
Abstract
Anandamide is a well-known agonist for the cannabinoid receptors. Along with endogenous anandamide other non-endocannabinoid N-acylethanolamines are also formed, apparently in higher amounts. These include mainly oleoylethanolamide (OEA), palmitoyelethanolamide (PEA) and linoleoylethanolamide (LEA), and they have biological activity by themselves being anorectic and anti-inflammatory. It appears that the major effect of dietary fat on the level of these molecules is in the gastrointestinal system, where OEA, PEA and LEA in the enterocytes may function as homeostatic signals, which are decreased by prolonged consumption of a high-fat diet. These lipid amides appear to mediate their signaling activity via activation of PPARα in the enterocyte followed by activation of afferent vagal fibers leading to the brain. Through this mechanism OEA, PEA and LEA may both reduce the consumption of a meal as well as increase the reward value of the food. Thus, they may function as homeostatic intestinal signals involving hedonic aspects that contribute to the regulation of the amounts of dietary fat to be ingested.
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Affiliation(s)
- Harald S Hansen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark.
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72
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Fowler CD, Kenny PJ. Nicotine aversion: Neurobiological mechanisms and relevance to tobacco dependence vulnerability. Neuropharmacology 2014; 76 Pt B:533-44. [PMID: 24055497 PMCID: PMC3858456 DOI: 10.1016/j.neuropharm.2013.09.008] [Citation(s) in RCA: 125] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Revised: 09/04/2013] [Accepted: 09/05/2013] [Indexed: 11/22/2022]
Abstract
Nicotine stimulates brain reward circuitries, most prominently the mesocorticolimbic dopamine system, and this action plays a critical in establishing and maintaining the tobacco smoking habit. Compounds that attenuate nicotine reward are considered promising therapeutic candidates for tobacco dependence, but many of these agents have other actions that limit their potential utility. Nicotine is also highly noxious, particularly at higher doses, and aversive reactions to nicotine after initial exposure can decrease the likelihood of developing a tobacco habit in many first time smokers. Nevertheless, relatively little is known about the mechanisms of nicotine aversion. The purpose of this review is to present recent new insights into the neurobiological mechanisms that regulate avoidance of nicotine. First, the role of the mesocorticolimbic system, so often associated with nicotine reward, in regulating nicotine aversion is highlighted. Second, genetic variation that modifies noxious responses to nicotine and thereby influences vulnerability to tobacco dependence, in particular variation in the CHRNA5-CHRNA3-CHRNB4 nicotinic acetylcholine receptor (nAChR) subunit gene cluster, will be discussed. Third, the role of the habenular complex in nicotine aversion, primarily medial habenular projections to the interpeduncular nucleus (IPN) but also lateral habenular projections to rostromedial tegmental nucleus (RMTg) and ventral tegmental area (VTA) are reviewed. Forth, brain circuits that are enriched in nAChRs, but whose role in nicotine avoidance has not yet been assessed, will be identified. Finally, the feasibility of developing novel therapeutic agents for tobacco dependence that act not by blocking nicotine reward but by enhancing nicotine avoidance will be considered. This article is part of a Special Issue entitled 'NIDA 40th Anniversary Issue'.
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Affiliation(s)
- Christie D Fowler
- Laboratory of Behavioral and Molecular Neuroscience, Department of Molecular Therapeutics, The Scripps Research Institute, Jupiter, FL 33458, USA; Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA
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Melis M, De Felice M, Lecca S, Fattore L, Pistis M. Sex-specific tonic 2-arachidonoylglycerol signaling at inhibitory inputs onto dopamine neurons of Lister Hooded rats. Front Integr Neurosci 2013; 7:93. [PMID: 24416004 PMCID: PMC3867690 DOI: 10.3389/fnint.2013.00093] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Accepted: 11/24/2013] [Indexed: 01/08/2023] Open
Abstract
Addiction as a psychiatric disorder involves interaction of inherited predispositions and environmental factors. Similarly to humans, laboratory animals self-administer addictive drugs, whose appetitive properties result from activation and suppression of brain reward and aversive pathways, respectively. The ventral tegmental area (VTA) where dopamine (DA) cells are located is a key component of brain reward circuitry, whereas the rostromedial tegmental nucleus (RMTg) critically regulates aversive behaviors. Reduced responses to either aversive intrinsic components of addictive drugs or to negative consequences of compulsive drug taking might contribute to vulnerability to addiction. In this regard, female Lister Hooded (LH) rats are more vulnerable than male counterparts to cannabinoid self-administration. We, therefore, took advantage of sex differences displayed by LH rats, and studied VTA DA neuronal properties to unveil functional differences. Electrophysiological properties of DA cells were examined performing either single cell extracellular recordings in anesthetized rats or whole-cell patch-clamp recordings in slices. In vivo, DA cell spontaneous activity was similar, though sex differences were observed in RMTg-induced inhibition of DA neurons. In vitro, DA cells showed similar intrinsic and synaptic properties. However, females displayed larger depolarization-induced suppression of inhibition (DSI) than male LH rats. DSI, an endocannabinoid-mediated form of short term plasticity, was mediated by 2-arachidonoylglycerol (2-AG) activating type 1-cannabinoid (CB1) receptors. We found that sex-dependent differences in DSI magnitude were not ascribed to CB1 number and/or function, but rather to a tonic 2-AG signaling. We suggest that sex specific tonic 2-AG signaling might contribute to regulate responses to aversive intrinsic properties to cannabinoids, thus resulting in faster acquisition/initiation of cannabinoid taking and, eventually, in progression to addiction.
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Affiliation(s)
- Miriam Melis
- Division of Neuroscience and Clinical Pharmacology, Department of Biomedical Sciences, University of Cagliari, Cittadella Universitaria di Monserrato Monserrato, Italy
| | - Marta De Felice
- Division of Neuroscience and Clinical Pharmacology, Department of Biomedical Sciences, University of Cagliari, Cittadella Universitaria di Monserrato Monserrato, Italy
| | | | - Liana Fattore
- Institute of Neuroscience, National Research Council, Cagliari Italy
| | - Marco Pistis
- Division of Neuroscience and Clinical Pharmacology, Department of Biomedical Sciences, University of Cagliari, Cittadella Universitaria di Monserrato Monserrato, Italy ; Institute of Neuroscience, National Research Council, Cagliari Italy
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Puligheddu M, Pillolla G, Melis M, Lecca S, Marrosu F, De Montis MG, Scheggi S, Carta G, Murru E, Aroni S, Muntoni AL, Pistis M. PPAR-alpha agonists as novel antiepileptic drugs: preclinical findings. PLoS One 2013; 8:e64541. [PMID: 23724059 PMCID: PMC3664607 DOI: 10.1371/journal.pone.0064541] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Accepted: 04/15/2013] [Indexed: 11/24/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) are involved in seizure mechanisms. Hence, nocturnal frontal lobe epilepsy was the first idiopathic epilepsy linked with specific mutations in α4 or β2 nAChR subunit genes. These mutations confer gain of function to nAChRs by increasing sensitivity toward acetylcholine. Consistently, nicotine elicits seizures through nAChRs and mimics the excessive nAChR activation observed in animal models of the disease. Treatments aimed at reducing nicotinic inputs are sought as therapies for epilepsies where these receptors contribute to neuronal excitation and synchronization. Previous studies demonstrated that peroxisome proliferator-activated receptors-α (PPARα), nuclear receptor transcription factors, suppress nicotine-induced behavioral and electrophysiological effects by modulating nAChRs containing β2 subunits. On these bases, we tested whether PPARα agonists were protective against nicotine-induced seizures. To this aim we utilized behavioral and electroencephalographic (EEG) experiments in C57BL/J6 mice and in vitro patch clamp recordings from mice and rats. Convulsive doses of nicotine evoked severe seizures and bursts of spike-waves discharges in ∼100% of mice. A single dose of the synthetic PPARα agonist WY14643 (WY, 80 mg/kg, i.p.) or chronic administration of fenofibrate, clinically available for lipid metabolism disorders, in the diet (0.2%) for 14 days significantly reduced or abolished behavioral and EEG expressions of nicotine-induced seizures. Acute WY effects were reverted by the PPARα antagonist MK886 (3 mg/kg, i.p.). Since neocortical networks are crucial in the generation of ictal activity and synchrony, we performed patch clamp recordings of spontaneous inhibitory postsynaptic currents (sIPSCs) from frontal cortex layer II/III pyramidal neurons. We found that both acute and chronic treatment with PPARα agonists abolished nicotine-induced sIPSC increases. PPARα within the CNS are key regulators of neuronal activity through modulation of nAChRs. These effects might be therapeutically exploited for idiopathic or genetically determined forms of epilepsy where nAChRs play a major role.
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Affiliation(s)
- Monica Puligheddu
- Department of Public Health, Clinical and Molecular Medicine, University of Cagliari, Cagliari, Italy
| | - Giuliano Pillolla
- Department of Public Health, Clinical and Molecular Medicine, University of Cagliari, Cagliari, Italy
| | - Miriam Melis
- Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy
- C.N.R. Neuroscience Institute, Cagliari, Italy
| | - Salvatore Lecca
- Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy
| | - Francesco Marrosu
- Department of Public Health, Clinical and Molecular Medicine, University of Cagliari, Cagliari, Italy
| | | | - Simona Scheggi
- Department of Molecular and Developmental Medicine, University of Siena, Siena, Italy
| | - Gianfranca Carta
- Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy
| | - Elisabetta Murru
- Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy
| | - Sonia Aroni
- Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy
| | | | - Marco Pistis
- Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy
- C.N.R. Neuroscience Institute, Cagliari, Italy
- * E-mail:
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