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Abstract
The endogenous opioid peptide system, comprised of enkephalins, endorphins, dynorphins, and nociceptin, is a highly complex neurobiological system. Opioid peptides are derived from four precursor molecules and undergo several processing events yielding over 20 unique opioid peptides. This diversity together with low in vivo concentration and complex processing and release dynamics has challenged research into each peptide's unique function. Despite the subsequent challenges in detecting and quantifying opioid peptides in vivo, researchers have pioneered several techniques to directly or indirectly assay the roles of opioid peptides during behavioral manipulations. In this review, we describe the limitations of the traditional techniques used to study the role of endogenous opioid peptides in food and drug reward and bring focus to the wealth of new techniques to measure endogenous opioid peptides in reward processing.
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Pham H, Seeley SL, D'Souza MS. Pharmacological activation of kappa opioid receptors in the nucleus accumbens core and ventral tegmental area increases the aversive effects of nicotine. Behav Pharmacol 2022; 33:266-281. [PMID: 35256559 DOI: 10.1097/fbp.0000000000000675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Aversive effects of nicotine play an important role in the development of nicotine dependence. However, neural substrates and/or brain regions that play a role in the aversive effects of nicotine have not been fully identified. Previous work done in our laboratory showed that systemic administration of kappa opioid receptors (KORs) agonist ±U50488 increased the aversive effects of nicotine. In this study, we assessed the effects of KOR activation in specific brain regions, namely, the nucleus accumbens (NAcc) core and ventral tegmental area (VTA) on the aversive effects of nicotine using the conditioned taste aversion model. Separate groups of Wistar rats were implanted with cannulae above either the NAcc core or the VTA. KOR agonist (±U50488) was bilaterally infused in the NAcc core (0, 0.3, and 3 ug/0.5 ul/side) or VTA (0, 0.3, 1.5, and 3 ug/0.5 ul/side) prior to receiving nicotine (0.4 mg/kg, base; s.c.) during conditioning. Bilateral infusion of the KOR agonist (3 ug/0.5 ul/side) in the NAcc core or the VTA increased the aversive effects of nicotine compared with respective saline controls. Together, these results suggest that pharmacological activation of the KORs in the NAcc core and VTA dose dependently modulate the aversive effects of nicotine. Because aversive effects of nicotine determine susceptibility to development of nicotine dependence, we can conclude that KOR activity in the NAcc and VTA after administration of nicotine may determine susceptibility to the development of nicotine dependence.
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Affiliation(s)
- Han Pham
- Department of Pharmaceutical and Biomedical Sciences, The Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio, USA
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3
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Bodnar RJ. Endogenous opioid modulation of food intake and body weight: Implications for opioid influences upon motivation and addiction. Peptides 2019; 116:42-62. [PMID: 31047940 DOI: 10.1016/j.peptides.2019.04.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 03/04/2019] [Accepted: 04/08/2019] [Indexed: 12/12/2022]
Abstract
This review is part of a special issue dedicated to Opioid addiction, and examines the influential role of opioid peptides, opioid receptors and opiate drugs in mediating food intake and body weight control in rodents. This review postulates that opioid mediation of food intake was an example of "positive addictive" properties that provide motivational drives to maintain opioid-seeking behavior and that are not subject to the "negative addictive" properties associated with tolerance, dependence and withdrawal. Data demonstrate that opiate and opioid peptide agonists stimulate food intake through homeostatic activation of sensory, metabolic and energy-related In contrast, general, and particularly mu-selective, opioid receptor antagonists typically block these homeostatically-driven ingestive behaviors. Intake of palatable and hedonic food stimuli is inhibited by general, and particularly mu-selective, opioid receptor antagonists. The selectivity of specific opioid agonists to elicit food intake was confirmed through the use of opioid receptor antagonists and molecular knockdown (antisense) techniques incapacitating specific exons of opioid receptor genes. Further extensive evidence demonstrated that homeostatic and hedonic ingestive situations correspondingly altered the levels and expression of opioid peptides and opioid receptors. Opioid mediation of food intake was controlled by a distributed brain network intimately related to both the appetitive-consummatory sites implicated in food intake as well as sites intimately involved in reward and reinforcement. This emergent system appears to sustain the "positive addictive" properties providing motivational drives to maintain opioid-seeking behavior.
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology, Queens College, City University of New York, United States; Psychology Doctoral Program and CUNY Neuroscience Collaborative, The Graduate Center of the City University of New York, United States.
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Harb MR, Almeida OFX. Pavlovian conditioning and cross-sensitization studies raise challenges to the hypothesis that overeating is an addictive behavior. Transl Psychiatry 2014; 4:e387. [PMID: 24780921 PMCID: PMC4012290 DOI: 10.1038/tp.2014.28] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 03/11/2014] [Accepted: 03/18/2014] [Indexed: 12/31/2022] Open
Abstract
Elevated glucocorticoid levels and sign tracking (ST) in Pavlovian conditioning are potential biomarkers of compulsive behaviors such as addiction. As overeating is sometimes viewed as a form of addictive behavior, we hypothesized that murine Pavlovian sign trackers would have a greater propensity to overeat and develop obesity. Using a food reward in the classical conditioning paradigm, we show that ST behavior is a robust conditioned response but not a predictor of eating and growth trajectories in mice, thus challenging the view that the development of obesity and drug addiction depend on identical mechanisms. This interpretation was supported by experiments which showed that overweight mice do not display cross-sensitization to an addictive drug (morphine), and conversely, that overweight morphine-sensitized animals do not overconsume a highly rewarding food. Although the rewarding/motivational effects of both food and drugs of abuse are mediated by similar neurochemical mechanisms, obesity and drug addiction represent a summation of other dysfunctional input and output pathways that lead to the emergence of two distinct disorders, each of which would deserve a specific pharmacotherapeutic approach.
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Affiliation(s)
- M R Harb
- NeuroAdaptations Group, Max Planck Institute of Psychiatry, Munich, Germany,Institute of Life & Health Sciences (ICVS), University of Minho, Braga, Portugal
| | - O F X Almeida
- NeuroAdaptations Group, Max Planck Institute of Psychiatry, Munich, Germany,Max Planck Institute of Psychiatry, Kraepelinstrasse 2–10, 80804 Munich, Germany. E-mail:
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Wise RA. Dual roles of dopamine in food and drug seeking: the drive-reward paradox. Biol Psychiatry 2013; 73:819-26. [PMID: 23044182 PMCID: PMC3548035 DOI: 10.1016/j.biopsych.2012.09.001] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Revised: 09/04/2012] [Accepted: 09/04/2012] [Indexed: 11/26/2022]
Abstract
The question of whether (or to what degree) obesity reflects addiction to high-energy foods often narrows to the question of whether the overeating of these foods causes the same long-term neuroadaptations as are identified with the late stages of addiction. Of equal or perhaps greater interest is the question of whether common brain mechanisms mediate the acquisition and development of eating and drug-taking habits. The earliest evidence on this question is rooted in early studies of brain stimulation reward. Lateral hypothalamic electrical stimulation can be reinforcing in some conditions and can motivate feeding in others. That stimulation of the same brain region should be both reinforcing and drive inducing is paradoxical; why should an animal work to induce a drive-like state such as hunger? This is known as the drive-reward paradox. Insights into the substrates of the drive-reward paradox suggest an answer to the controversial question of whether the dopamine system--a system downstream from the stimulated fibers of the lateral hypothalamus--is more critically involved in wanting or in liking of various rewards including food and addictive drugs. That the same brain circuitry is implicated in the motivation for and the reinforcement by both food and addictive drugs extends the argument for a common mechanism underlying compulsive overeating and compulsive drug taking.
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Affiliation(s)
- Roy A. Wise
- Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, 251 Bayview Blvd., Baltimore, MD 21224, tel: 443-740-2468, fax: 443-740-2827
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Miner P, Shimonova L, Khaimov A, Borukhova Y, Ilyayeva E, Ranaldi R, Bodnar RJ. General, kappa, delta and mu opioid receptor antagonists 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 2012; 1443:34-51. [DOI: 10.1016/j.brainres.2012.01.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Revised: 12/16/2011] [Accepted: 01/07/2012] [Indexed: 10/14/2022]
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Fulton S. Appetite and reward. Front Neuroendocrinol 2010; 31:85-103. [PMID: 19822167 DOI: 10.1016/j.yfrne.2009.10.003] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Revised: 10/06/2009] [Accepted: 10/06/2009] [Indexed: 12/14/2022]
Abstract
The tendency to engage in or maintain feeding behaviour is potently influenced by the rewarding properties of food. Affective and goal-directed behavioural responses for food have been assessed in response to various physiological, pharmacological and genetic manipulations to provide much insight into the neural mechanisms regulating motivation for food. In addition, several lines of evidence tie the actions of metabolic signals, neuropeptides and neurotransmitters to the modulation of the reward-relevant circuitry including midbrain dopamine neurons and corticolimbic nuclei that encode emotional and cognitive aspects of feeding. Along these lines, this review pulls together research describing the peripheral and central signalling molecules that modulate the rewarding effects of food and the underlying neural pathways.
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Affiliation(s)
- Stephanie Fulton
- CRCHUM and Montreal Diabetes Research Center, Department of Nutrition, Faculty of Medicine, University of Montreal, Montreal, QC, Canada.
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Narayanan NS, Guarnieri DJ, DiLeone RJ. Metabolic hormones, dopamine circuits, and feeding. Front Neuroendocrinol 2010; 31:104-12. [PMID: 19836414 PMCID: PMC2813908 DOI: 10.1016/j.yfrne.2009.10.004] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2009] [Revised: 10/12/2009] [Accepted: 10/13/2009] [Indexed: 10/20/2022]
Abstract
Recent evidence has emerged demonstrating that metabolic hormones such as ghrelin and leptin can act on ventral tegmental area (VTA) midbrain dopamine neurons to influence feeding. The VTA is the origin of mesolimbic dopamine neurons that project to the nucleus accumbens (NAc) to influence behavior. While blockade of dopamine via systemic antagonists or targeted gene delete can impair food intake, local NAc dopamine manipulations have little effect on food intake. Notably, non-dopaminergic manipulations in the VTA and NAc produce more consistent effects on feeding and food choice. More recent genetic evidence supports a role for the substantia nigra-striatal dopamine pathways in food intake, while the VTA-NAc circuit is more likely involved in higher-order aspects of food acquisition, such as motivation and cue associations. This rich and complex literature should be considered in models of how peripheral hormones influence feeding behavior via action on the midbrain circuits.
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Bruijnzeel AW. kappa-Opioid receptor signaling and brain reward function. BRAIN RESEARCH REVIEWS 2009; 62:127-46. [PMID: 19804796 PMCID: PMC2787673 DOI: 10.1016/j.brainresrev.2009.09.008] [Citation(s) in RCA: 146] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2009] [Revised: 09/28/2009] [Accepted: 09/28/2009] [Indexed: 02/06/2023]
Abstract
The dynorphin-like peptides have profound effects on the state of the brain reward system and human and animal behavior. The dynorphin-like peptides affect locomotor activity, food intake, sexual behavior, anxiety-like behavior, and drug intake. Stimulation of kappa-opioid receptors, the endogenous receptor for the dynorphin-like peptides, inhibits dopamine release in the striatum (nucleus accumbens and caudate putamen) and induces a negative mood state in humans and animals. The administration of drugs of abuse increases the release of dopamine in the striatum and mediates the concomitant release of dynorphin-like peptides in this brain region. The reviewed studies suggest that chronic drug intake leads to an upregulation of the brain dynorphin system in the striatum and in particular in the dorsal part of the striatum/caudate putamen. This might inhibit drug-induced dopamine release and provide protection against the neurotoxic effects of high dopamine levels. After the discontinuation of chronic drug intake these neuroadaptations remain unopposed which has been suggested to contribute to the negative emotional state associated with drug withdrawal and increased drug intake. kappa-Opioid receptor agonists have also been shown to inhibit calcium channels. Calcium channel inhibitors have antidepressant-like effects and inhibit the release of norepinephrine. This might explain that in some studies kappa-opioid receptor agonists attenuate nicotine and opioid withdrawal symptomatology. A better understanding of the role of dynorphins in the regulation of brain reward function might contribute to the development of novel treatments for mood disorders and other disorders that stem from a dysregulation of the brain reward system.
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Affiliation(s)
- Adrie W Bruijnzeel
- Department of Psychiatry, McKnight Brain Institute, University of Florida, Gainesville, 32610, USA.
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Chiu CT, Ma T, Ho IK. Methamphetamine-induced behavioral sensitization in mice: alterations in mu-opioid receptor. J Biomed Sci 2006; 13:797-811. [PMID: 16847721 PMCID: PMC2925105 DOI: 10.1007/s11373-006-9102-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2006] [Accepted: 06/21/2006] [Indexed: 11/28/2022] Open
Abstract
We had previously demonstrated that opioid receptors contribute to the induction and expression of behavioral sensitization induced by repeated daily injection with 2.5 mg/kg of methamphetamine for 7 days. Using the same regimen, the present study investigated the alterations in mu-opioid receptor during the induction (on days 2, 5, and 8) and expression (on days 11 and 21) periods of behavioral sensitization. Radioligand binding revealed that the maximal binding of mu-opioid receptor was not changed on days 2 and 5, but down-regulated on day 8. After cessation of drug treatment, the maximal binding of mu-opioid receptor gradually and time-dependently returned to normal level on day 11 and up-regulated on day 21. In contrast, no changes in delta- and kappa-opioid receptors were detectable on any given day examined. The potency of DAMGO for [(35)S]-GTPgammaS coupling was enhanced on days 2, 5, 11, and 21. Moreover, 1 muM of naltrexone or beta-chlornaltrexamine significantly suppressed the basal [(35)S]-GTPgammaS coupling on days 2, 11, and 21. These findings indicate enhanced responsiveness and elevated constitutive activity of mu-opioid receptor. In summary, our data clearly demonstrate that alterations in mu-opioid receptor are involved in and may contribute to the sensitization to locomotor stimulating effect of methamphetamine.
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Affiliation(s)
| | | | - Ing K. Ho
- To whom correspondence should be addressed. Fax +1-601-984-1637,
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Bodnar RJ, Lamonte N, Israel Y, Kandov Y, Ackerman TF, Khaimova E. Reciprocal opioid-opioid interactions between the ventral tegmental area and nucleus accumbens regions in mediating mu agonist-induced feeding in rats. Peptides 2005; 26:621-9. [PMID: 15752577 DOI: 10.1016/j.peptides.2004.11.007] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2004] [Revised: 11/04/2004] [Accepted: 11/08/2004] [Indexed: 11/17/2022]
Abstract
Feeding elicited by the mu-selective agonist, [D-Ala2, M-Phe4, Gly-ol5]-encephalin administered into the nucleus accumbens is blocked by accumbal pre-treatment with mu, delta1, delta2 and kappa, but not mu1 opioid antagonists. Correspondingly, mu-agonist-induced feeding elicited from the ventral tegmental area is blocked by ventral tegmental area pre-treatment with mu and kappa, but not delta opioid antagonists. A bi-directional opioid-opioid feeding interaction has been firmly established such that mu-agonist-induced feeding elicited from the ventral tegmental area is blocked by accumbal naltrexone, and that accumbal mu-agonist-induced feeding is blocked by naltrexone pre-treatment in the ventral tegmental area. To determine which opioid receptor subtypes mediate the regional bi-directional opioid-opioid feeding interactions between these two sites, the present study examined the dose-dependent ability of either general (naltrexone), mu (beta-funaltrexamine), kappa (nor-binaltorphamine) or delta (naltrindole) opioid antagonists administered into one site to block mu-agonist-induced feeding elicited from the other site. General, mu and kappa, but not delta opioid receptor antagonist pre-treatment in the ventral tegmental area dose-dependently reduced mu-agonist-induced feeding elicited from the nucleus accumbens. General, mu and delta, and to a lesser degree kappa, opioid receptor antagonist pre-treatment in the nucleus accumbens dose-dependently reduced mu-agonist-induced feeding elicited from the ventral tegmental area. Thus, multiple, but different opioid receptor subtypes are involved in mediating opioid-opioid feeding interactions between the nucleus accumbens and ventral tegmental area regions.
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, 65-30 Kissena Blvd., Flushing, NY 11367, USA.
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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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Bodnar RJ. Endogenous opioids and feeding behavior: a 30-year historical perspective. Peptides 2004; 25:697-725. [PMID: 15165728 DOI: 10.1016/j.peptides.2004.01.006] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2004] [Revised: 01/15/2004] [Accepted: 01/16/2004] [Indexed: 11/25/2022]
Abstract
This invited review, based on the receipt of the Third Gayle A. Olson and Richard D. Olson Prize for the publication of the outstanding behavioral article published in the journal Peptides in 2002, examines the 30-year historical perspective of the role of the endogenous opioid system in feeding behavior. The review focuses on the advances that this field has made over the past 30 years as a result of the timely discoveries that were made concerning this important neuropeptide system, and how these discoveries were quickly applied to the analysis of feeding behavior and attendant homeostatic processes. The discoveries of the opioid receptors and opioid peptides, and the establishment of their relevance to feeding behavior were pivotal in studies performed in the 1970s. The 1980s were characterized by the establishment of opioid receptor subtype agonists and antagonists and their relevance to the modulation of feeding behavior as well as by the use of general opioid antagonists in demonstrating the wide array of ingestive situations and paradigms involving the endogenous opioid system. The more recent work from the 1990s to the present, utilizes the advantages created by the cloning of the opioid receptor genes, the development of knockout and knockdown techniques, the systematic utilization of a systems neuroscience approach, and establishment of the reciprocity of how manipulations of opioid peptides and receptors affect feeding behavior with how feeding states affect levels of opioid peptides and receptors. The role of G-protein effector systems in opioid-mediated feeding responses, which was the subject of the prize-winning article, is then reviewed.
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Subprogram, Queens College, City University of New York, 65-30 Kissena Blvd., Flushing, NY 11367, USA.
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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: 0.6] [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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Paolone G, Burdino R, Badiani A. Dissociation in the modulatory effects of environmental novelty on the locomotor, analgesic, and eating response to acute and repeated morphine in the rat. Psychopharmacology (Berl) 2003; 166:146-55. [PMID: 12545329 DOI: 10.1007/s00213-002-1321-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2002] [Accepted: 10/16/2002] [Indexed: 10/20/2022]
Abstract
RATIONALE We have previously shown that environmental novelty can potentiate the activating effects of morphine and the development of sensitization to this effect. OBJECTIVES. Our main goal was to determine whether environmental novelty can also modulate the prophagic (time spent eating and food intake; experiment 1) and/or the analgesic (tail-flick test; experiments 2 and 3) effect of morphine, as well as the development of tolerance or sensitization to these effects. METHODS In experiment 1, two groups of rats were administered seven intraperitoneal (i.p.) injections of either saline or morphine (4.0 mg/kg) either in their home cages (home groups) or in a distinct environment (novelty groups). After 7 days of withdrawal, both groups underwent a morphine challenge (4.0 mg/kg, i.p.). In experiment 2, home and novelty rats were administered four doses of morphine (0.0, 2.0, 4.0, and 8.0 mg/kg, i.p.) following a counterbalanced order. In experiment 3, home and novelty rats were administered eight intraperitoneal (i.p.) injections of either saline or morphine (8.0 mg/kg) and then given a morphine challenge (4.0 mg/kg). RESULTS Environmental novelty enhanced the locomotor activating effect of morphine and the expression of sensitization to this effect (even after a period of withdrawal). Environmental novelty had relatively little effect on morphine-induced eating, and no effect on morphine-induced analgesia. CONCLUSIONS Environmental context can have very different consequences on distinct drug effects as well as on distinct neurobehavioral adaptations to the same drug treatment (e.g., psychomotor sensitization versus analgesic tolerance).
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Affiliation(s)
- Giovanna Paolone
- Department of Human Physiology and Pharmacology Vittorio Erspamer, University of Rome La Sapienza, Rome, Italy
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Echo JA, Lamonte N, Ackerman TF, Bodnar RJ. Alterations in food intake elicited by GABA and opioid agonists and antagonists administered into the ventral tegmental area region of rats. Physiol Behav 2002; 76:107-16. [PMID: 12175594 DOI: 10.1016/s0031-9384(02)00690-x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Food intake is significantly increased following administration of mu-selective opioid agonists into the ventral tegmental area (VTA) region acting through multiple local opioid receptor subtypes. Since GABA receptor agonists in the VTA region are capable of eliciting feeding, the present study investigated whether feeding elicited by the mu-selective opioid agonist [D-Ala(2), NMe(4), Gly-ol(5)]-enkephalin (DAMGO) in the VTA region was altered by pretreatment into the same site with equimolar doses of either GABA(A) (bicuculline) or GABA(B) (saclofen) antagonists, and further, whether pretreatment with either general opioid or selective GABA receptor antagonists decreased feeding elicited by GABA(A) (muscimol) or GABA(B) (baclofen) agonists in the VTA region. DAMGO-induced feeding in the VTA region was dose-dependently decreased following pretreatment with either GABA(A) or GABA(B) antagonists in the absence of significant alterations in food intake by the antagonists per se. However, the presence of short-lived seizures following bicuculline in the VTA region suggests that this ingestive effect was caused by nonspecific actions. In contrast, GABA(B) receptors are involved in the full expression of mu-opioid agonist-induced feeding in this region since saclofen failed to elicit either seizure activity or a conditioned taste aversion. Pretreatment with naltrexone in the VTA region reduced intake elicited by baclofen, but not muscimol. Finally, baclofen-induced feeding was significantly reduced by saclofen, but not bicuculline, pretreatment in the VTA region. Therefore, possible coregulation between GABA(B) and opioid receptors in the VTA region, as suggested by immunocytochemical evidence, is supported by these behavioral effects upon ingestion.
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Affiliation(s)
- Joyce A Echo
- 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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17
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Lamonte N, Echo JA, Ackerman TF, Christian G, Bodnar RJ. Analysis of opioid receptor subtype antagonist effects upon mu opioid agonist-induced feeding elicited from the ventral tegmental area of rats. Brain Res 2002; 929:96-100. [PMID: 11852035 DOI: 10.1016/s0006-8993(01)03382-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The present study examined opioid receptor(s) mediation of feeding elicited by mu opioid agonists in the ventral tegmental area using general or selective opioid antagonist pretreatment. Naltrexone as well as equimolar doses of selective mu and kappa, but not delta opioid antagonists in the ventral tegmental area significantly reduced mu agonist-induced feeding, indicating a pivotal role for these receptor subtypes in the full expression of this response.
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MESH Headings
- Animals
- Appetite Regulation/drug effects
- Appetite Regulation/physiology
- Dose-Response Relationship, Drug
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/pharmacology
- Feeding Behavior/drug effects
- Feeding Behavior/physiology
- Male
- Naltrexone/analogs & derivatives
- Naltrexone/pharmacology
- Narcotic Antagonists/pharmacology
- Narcotics/pharmacology
- Neural Pathways/drug effects
- Neural Pathways/metabolism
- Neurons/drug effects
- Neurons/metabolism
- Nucleus Accumbens/drug effects
- Nucleus Accumbens/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptors, Opioid, delta/agonists
- Receptors, Opioid, delta/antagonists & inhibitors
- Receptors, Opioid, delta/metabolism
- Receptors, Opioid, kappa/agonists
- Receptors, Opioid, kappa/antagonists & inhibitors
- Receptors, Opioid, kappa/metabolism
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/antagonists & inhibitors
- Receptors, Opioid, mu/metabolism
- Synaptic Transmission/drug effects
- Synaptic Transmission/physiology
- Ventral Tegmental Area/drug effects
- Ventral Tegmental Area/metabolism
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Affiliation(s)
- Nicole Lamonte
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, 65-30 Kissena Blvd., Flushing, NY 11367, USA
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18
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Ragnauth A, Ruegg H, Bodnar RJ. Evaluation of opioid receptor subtype antagonist effects in the ventral tegmental area upon food intake under deprivation, glucoprivic and palatable conditions. Brain Res 1997; 767:8-16. [PMID: 9365010 DOI: 10.1016/s0006-8993(97)00539-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Opioid receptor subtype antagonists differentially alter food intake under deprivation (24 h), glucoprivic (2-deoxy-D-glucose, 500 mg/kg, i.p.) or palatable (10% sucrose) conditions with mu (beta-funaltrexamine) and kappa (nor-binaltorphamine), but not delta1 ([D-Ala2,Leu5,Cys6]enkephalin) opioid antagonists reducing each form of intake following ventricular microinjection. Both mu and kappa opioid antagonists microinjected into either the hypothalamic paraventricular nucleus or the nucleus accumbens reduce intake under deprivation and glucoprivic conditions. Palatable intake is reduced by both antagonists in the paraventricular nucleus, but only mu antagonists are active in the accumbens. Food intake is stimulated by mu and delta, but not kappa, opioid agonists microinjected into the ventral tegmental area. The present study examined whether food intake under either deprivation, glucoprivic or palatable conditions was altered by bilateral administration of general (naltrexone), mu, kappa, delta1 or delta2 (naltrindole isothiocyanate) opioid antagonists into the ventral tegmental area. Deprivation (24 h)-induced feeding was significantly reduced by high (50 microg), but not lower (10-20 microg) doses of naltrexone (21%), and by delta2 (4 microg, 19%) antagonism in the ventral tegmental area. 2-Deoxy-D-glucose (500 mg/kg, i.p.)-induced hyperphagia was significantly reduced by high (50 microg), but not lower (20 microg) doses of naltrexone (64%), and by delta2 (4 microg, 27%) antagonism in the ventral tegmental area. Sucrose (10%) intake was significantly reduced by naltrexone (20-50 microg, 25-39%) and delta2 (4 microg, 25%) antagonism in the ventral tegmental area. Neither mu, kappa nor delta1 antagonists were effective in reducing any form of intake following microinjection into the ventral tegmental area. These data indicate that the ventral tegmental area plays a relatively minor role in the elicitation of these forms of food intake, and that delta2, rather than mu, kappa or delta1 opioid receptors appear responsible for mediation of these forms of intake by this nucleus.
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Affiliation(s)
- A Ragnauth
- Department of Psychology, City University of New York, Flushing 11367, USA
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19
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Abstract
This study examined the effects of specific antagonists to kappa- and mu-opioid receptors on the feeding induced by injecting galanin into the lateral cerebral ventricle (LCV). Galanin injected into the lateral cerebral ventricle of sated rats stimulated the consumption of high-fat diet when compared to controls injected with saline vehicle. The mu-opioid receptor antagonist, CTOP, completely abolished galanin-induced feeding in sated rats whereas the kappa-opioid receptor antagonist, nor-BNI, had no effect on galanin-induced feeding. Neither CTOP nor nor-BNI alone produced any change in food consumption in sated rats. In fasted rats, on the other hand, nor-BNI significantly decreased consumption of a high-fat diet (> 83%) when compared to animals treated with the saline vehicle, whereas CTOP had no significant effect. These findings suggest that galanin-induced feeding of a high-fat diet is selectively modulated by a pathway involving mu-opioid receptors whereas feeding induced by fasting is dependent on a pathway mediated by kappa-opioid receptors. These data also suggest that galanin does not mediate the feeding response after fasting.
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MESH Headings
- Animals
- Dietary Fats/pharmacology
- Eating/drug effects
- Fasting
- Galanin/pharmacology
- Male
- Naltrexone/analogs & derivatives
- Naltrexone/pharmacology
- Narcotic Antagonists/pharmacology
- Rats
- Rats, Sprague-Dawley
- Receptors, Opioid/drug effects
- Receptors, Opioid/physiology
- Receptors, Opioid, kappa/drug effects
- Receptors, Opioid, kappa/physiology
- Receptors, Opioid, mu/drug effects
- Receptors, Opioid, mu/physiology
- Somatostatin/analogs & derivatives
- Somatostatin/pharmacology
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Affiliation(s)
- C Barton
- Pennington Biomedical Research Center, Louisiana State University, Baton Rouge 70808-4124, USA
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20
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Badiani A, Leone P, Noel MB, Stewart J. Ventral tegmental area opioid mechanisms and modulation of ingestive behavior. Brain Res 1995; 670:264-76. [PMID: 7743190 DOI: 10.1016/0006-8993(94)01281-l] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In this paper we report on the effects of intra-VTA infusion of opioid agonists on rat ingestive behavior in a variety of experimental contexts. When the animals were tested outside of their home cages surrounded only by food-pellets (Experiment 1), the injection of the mu-opioid agonist DAMGO, but not the kappa-opioid agonist U-50,488H, into the ventral tegmental area facilitated food-related behaviors, decreasing the latency to feed and increasing the number of interactions with food. When, as in Experiment 2, gnawable objects and a drinking tube were also available, intra-VTA DAMGO gnawing and drinking behaviors, whereas the effects on feeding were negligible. These effects intra-VTA DAMGO increased were greatly enhanced in rats that underwent repeated treatments with amphetamine. On the other hand, when food-related behaviors were studied in a home-cage, where access to the food supply was achieved by entry into a tunnel, latency to feed and total food-intake were not enhanced in tests made during either the dark or the light phase (Experiment 3 and 4). This was true whether powdered standard lab chow or a highly palatable food was available. It appears that when a number of alternative incentive stimuli are available, increases in dopamine transmission such as that induced by intra-VTA DAMGO may ultimately have the effect of interfering with behavior normally directed primarily to one of these stimuli, by enhancing the salience of others. These effects bears some resemblance to the effects of tail-pinch and electrical brain stimulation of the medial forebrain bundle-lateral hypothalamic area on the responses to natural incentive stimuli.
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MESH Headings
- 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer
- Analysis of Variance
- Animals
- Endorphins/agonists
- Endorphins/physiology
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
- Enkephalin, D-Penicillamine (2,5)-
- Enkephalins/pharmacology
- Feeding Behavior/drug effects
- Feeding Behavior/physiology
- Male
- Pyrrolidines/pharmacology
- Rats
- Receptors, Opioid, delta/agonists
- Receptors, Opioid, kappa/agonists
- Receptors, Opioid, mu/agonists
- Ventral Tegmental Area/physiology
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Affiliation(s)
- A Badiani
- Center for Studies in Behavioral Neurobiology, Concordia University, Montréal, Québec, Canada
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21
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Hawkins MF, Fuller RD, Baumeister AA, McCallum MD. Effects in the rat of intranigral morphine and DAGO on eating and gnawing induced by stress. Pharmacol Biochem Behav 1994; 49:737-40. [PMID: 7862730 DOI: 10.1016/0091-3057(94)90094-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Stress produced by pinching the tail is known to increase feeding behavior in rats, and endogenous opioids have been implicated in the mediation of this effect. We have reported previously that a nonspecific opioid antagonist and a mu-selective antagonist decrease this stress-induced eating (SIE) when they are microinjected into the substantia nigra (SN). The present study investigated the possibility that activation of opioid receptors in the SN might also alter SIE. Because oral stereotypy and nociception are affected by opioid mechanisms in the SN, measurements of gnawing and of tail flick and hot plate response latencies were also made. Bilateral injection of morphine (0.1-20 nmol) and the mu-selective agonist D-Ala2,N-Me-Phe4,Gly5-ol-enkephalin (DAGO; 0.03-1 nmol) increased response latency on the hot plate test and decreased gnawing produced by tail pinch. Tail flick latency and SIE were not affected. It is concluded that activation of opioid receptors in the SN does not produce an alteration in SIE as has been seen with opioid antagonists.
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Affiliation(s)
- M F Hawkins
- Louisiana State University, Department of Psychology, Baton Rouge 70803
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22
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Nencini P, Valeri P. The role of opioid mechanisms in the anorectic effects of stimulants: U50,488H enhances amphetamine inhibition of free feeding in rats. Pharmacol Biochem Behav 1994; 48:63-8. [PMID: 7913232 DOI: 10.1016/0091-3057(94)90499-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The influences of the kappa-opiate agonist U50,488H (U50; 4 mg/kg IP), the neuroleptic haloperidol (HAL; 0.3 mg/kg IP), and MK-801 (0.2 mg/kg IP), a noncompetitive antagonist for NMDA receptors, were compared on the effects of nine days of d-amphetamine (AMPH) treatment (3 mg/kg IP) on food and water intake and urine output. AMPH prevented feeding stimulation produced by U50 during the first 2 h, whereas U50 inhibited the hyperphagic phase that rats showed between 2 and 5 h after AMPH administration. Tolerance did not develop to the first 2-h suppression of feeding; in contrast, the late hyperphagic phase slowly recovered across the nine days of treatment. Combined administration of the two drugs barely affected water intake but considerably increased urine output. Unlike U50, HAL left the late hyperphagic response to AMPH unchanged and delayed the development of hyperdipsia. In our study MK-801 had one effect only: It significantly reduced amphetamine diuresis. These results suggest that by inhibiting the late hyperphagic response U50 enhances the anorectic effects of AMPH, but that dopamine probably has no direct role in this interaction.
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Affiliation(s)
- P Nencini
- Institute of Medical Pharmacology, University of Rome La Sapienza, Italy
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23
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Carr KD, Papadouka V. The role of multiple opioid receptors in the potentiation of reward by food restriction. Brain Res 1994; 639:253-60. [PMID: 8205479 DOI: 10.1016/0006-8993(94)91738-8] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Chronic food restriction and weight loss were previously shown to produce a naltrexone-reversible facilitation of perifornical lateral hypothalamic self-stimulation. In the present study, high affinity receptor-selective antagonists were used to determine the particular opioid receptor type(s) that mediates the facilitation of reward by food restriction. Separate groups of food-restricted and ad libitum fed rats were used to conduct i.c.v. dose-response studies with TCTAP (mu), norbinaltorphimine (kappa), and naltrindole (delta). The highest dose of naltrindole (50.0 nmol) raised self-stimulation threshold independently of feeding condition. This suggests that delta opioid activity is involved in self-stimulation under basal conditions and may explain previous findings that high systemic doses of naloxone or naltrexone reduce self-stimulation. The highest doses of TCTAP and norbinaltorphimine (5.0 and 50.0 nmol, respectively) reversed the lowering of self-stimulation threshold produced by food restriction while having no effect on thresholds of ad libitum fed rats. These results suggest that state-dependent mu and kappa opioid activity facilitate reward. Since food restriction is known to increase the rewarding effect of food and drugs of abuse, the opioid mechanism identified in the present study may mediate adaptive behavior and, under some circumstances, pathological behavior. The possible relation of state-dependent opioid activity to Anorexia Nervosa, binge eating, and the high comorbidity of eating disorders and substance abuse is discussed.
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MESH Headings
- Animals
- Behavior, Animal/drug effects
- Brain/physiology
- Conditioning, Operant/drug effects
- Dose-Response Relationship, Drug
- Food Deprivation/physiology
- Injections, Intraventricular
- Male
- Naltrexone/analogs & derivatives
- Naltrexone/pharmacology
- Narcotic Antagonists
- Oligopeptides/pharmacology
- Rats
- Rats, Sprague-Dawley
- Receptors, Opioid/drug effects
- Receptors, Opioid/physiology
- Receptors, Opioid, delta/antagonists & inhibitors
- Receptors, Opioid, delta/physiology
- Receptors, Opioid, kappa/antagonists & inhibitors
- Receptors, Opioid, kappa/physiology
- Receptors, Opioid, mu/antagonists & inhibitors
- Receptors, Opioid, mu/physiology
- Reward
- Self Stimulation
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Affiliation(s)
- K D Carr
- Millhauser Laboratories, Department of Psychiatry, New York University Medical Center, New York 10016
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24
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Pickel VM, Chan J, Sesack SR. Cellular substrates for interactions between dynorphin terminals and dopamine dendrites in rat ventral tegmental area and substantia nigra. Brain Res 1993; 602:275-89. [PMID: 8095430 DOI: 10.1016/0006-8993(93)90693-h] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Dynorphin and other kappa opioid agonists are thought to elicit aversive actions and changes in motor activity through direct or indirect modulation of dopamine neurons in ventral tegmental area (VTA) and substantia nigra (SN), respectively. We comparatively examined the immunoperoxidase localization of anti-dynorphin A antiserum in sections through the VTA and SN of adult rat brain to assess whether there were common or differential distributions of this opioid peptide relative to the dopamine neurons. We also more directly examined the relationship between dynorphin terminals and dopamine neurons in VTA and SN by combining immunoperoxidase labeling of rabbit dynorphin antiserum and immunogold-silver detection of mouse antibodies against tyrosine hydroxylase (TH) in single sections through the VTA and SN. Light microscopy showed dynorphin-like immunoreactivity (DY-LI) in varicose processes. These were relatively sparse in VTA and were unevenly distributed in the SN, with little labeling in the pars compacta (pcSN) and the highest density of DY-LI in the medial and lateral pars reticulata (prSN). Electron microscopy established that the regional differences were attributed to differences in density (number/unit area) of immunoreactive profiles. The profiles containing DY-LI were designated as axon terminals based on having diameters greater than 0.1 micron, few microtubules and many synaptic vesicles. In both the VTA and SN, the dynorphin-labeled terminals contained primarily small (35-40 nm) clear vesicles. These vesicles were rimmed with peroxidase immunoreactivity and were often seen clustered above axodendritic synapses. These synaptic specializations were usually symmetric; however a few asymmetric densities also were formed by immunoreactive terminals in both VTA and SN. Additionally, most of the dynorphin-labeled terminals contained 1-2, but occasionally 7 or more intensely peroxidase positive dense core vesicles (DCVs). Approximately 60% of the DCVs were located near axolemmal surfaces. The axolemmal surfaces contacted by immunoreactive DCVs were more often apposed to dendrites in the VTA; while in the SN other axon terminals were the most commonly apposed neuronal profiles. In both regions, a substantial proportion of the plasmalemmal surface in contact with the labeled DCVs was apposed to astrocytic processes.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- V M Pickel
- Department of Neurology and Neuroscience, Cornell University Medical College, New York, NY 10021
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25
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Kalivas PW. Neurotransmitter regulation of dopamine neurons in the ventral tegmental area. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 1993; 18:75-113. [PMID: 8096779 DOI: 10.1016/0165-0173(93)90008-n] [Citation(s) in RCA: 571] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Over the last 10 years there has been important progress towards understanding how neurotransmitters regulate dopaminergic output. Reasonable estimates can be made of the synaptic arrangement of afferents to dopamine and non-dopamine cells in the ventral tegmental area (VTA). These models are derived from correlative findings using a variety of techniques. In addition to improved lesioning and pathway-tracing techniques, the capacity to measure mRNA in situ allows the localization of transmitters and receptors to neurons and/or axon terminals in the VTA. The application of intracellular electrophysiology to VTA tissue slices has permitted great strides towards understanding the influence of transmitters on dopamine cell function, as well as towards elucidating relative synaptic organization. Finally, the advent of in vivo dialysis has verified the effects of transmitters on dopamine and gamma-aminobutyric acid transmission in the VTA. Although reasonable estimates can be made of a single transmitter's actions under largely pharmacological conditions, our knowledge of how transmitters work in concert in the VTA to regulate the functional state of dopamine cells is only just emerging. The fact that individual transmitters can have seemingly opposite effects on dopaminergic function demonstrates that the actions of neurotransmitters in the VTA are, to some extent, state-dependent. Thus, different transmitters perform similar functions or the same transmitter may perform opposing functions when environmental circumstances are altered. Understanding the dynamic range of a transmitter's action and how this couples in concert with other transmitters to modulate dopamine neurons in the VTA is essential to defining the role of dopamine cells in the etiology and maintenance of neuropsychiatric disorders. Further, it will permit a more rational exploration of drugs possessing utility in treating disorders involving dopamine transmission.
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Affiliation(s)
- P W Kalivas
- Alcohol and Drug Abuse Program, Washington State University, Pullman 99164-6530
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26
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Schindler CW, Goldberg SR, Katz JL. Pharmacological specificity of enhanced sensitivity to naltrexone in rats. Psychopharmacology (Berl) 1993; 110:60-8. [PMID: 7870900 DOI: 10.1007/bf02246951] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Rats treated weekly with cumulative doses (1-100 mg/kg, IP) of naltrexone develop an enhanced sensitivity to the operant response-rate decreasing effect of naltrexone. In the present experiment the pharmacological specificity of that enhanced sensitivity was determined by testing a variety of drugs for cross-sensitivity to naltrexone. Cross-sensitivity was evaluated with two procedures. In one, dose-effect functions were determined for each of the test compounds before and after the development of enhanced sensitivity to naltrexone in a single group of rats. In the second procedure, one group of rats was made sensitive to naltrexone, while a second was not. Test compounds were then evaluated in both groups. For both procedures, a shift to the left in the dose-effect functions similar to naltrexone was considered evidence of cross-sensitivity. Of the opioid antagonists tested, only naloxone showed clear cross-sensitivity to naltrexone, although MR 2266 and diprenorphine also showed evidence of cross-sensitivity. The opioid antagonist quadazocine did not show cross-sensitivity to naltrexone on the day of testing, although some evidence of cross-sensitivity was evident 24 h later. In addition, the dose-effect function for d-amphetamine was significantly changed following naltrexone treatment. No evidence of cross-sensitivity was observed for the optical isomer of naloxone, d-naloxone, or for naloxone's quaternary derivative, naloxone methiodide. None of the opioid agonists or agonist-antagonists tested showed cross-sensitivity to naltrexone (i.e. morphine, U-50, 488H, ethylketocyclazocine, N-allylnormetazocine and pentazocine). The non-opioid drugs chlordiazepoxide and phencyclidine also failed to show evidence of cross-sensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- C W Schindler
- Preclinical Pharmacology Laboratory, National Institute on Drug Abuse, Baltimore, MD 21224
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27
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Badiani A, Stewart J. Enhancement of the prophagic but not of the antidipsogenic effect of U-50, 488H after chronic amphetamine. Pharmacol Biochem Behav 1993; 44:77-86. [PMID: 8430131 DOI: 10.1016/0091-3057(93)90283-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Two groups of rats were treated with seven daily injections of either saline or d-amphetamine (3 mg/kg IP). On the 2 days following the last injection, rats were tested according to a counterbalanced experimental design, each animal receiving, immediately prior to the beginning of the dark phase, saline on one day and the highly selective kappa-opioid agonist trans- +/- 3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]-benzene- acetamide methanesulfonate hydrate [U-50,488H (U50)] on the other. A microcomputer-controlled data acquisition system was used for the structural analysis of the feeding and drinking responses to amphetamine and U50. U50 enhanced feeding and depressed drinking in the first hour. The increased food intake was probably the result of the effect of U50 on the development of satiation and duration of satiety. Chronic amphetamine potentiated the prophagic effect but not the antidipsogenic effect of U50. The structural analysis demonstrated that the characteristics of the prophagic effect of U50 were amplified but not changed.
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Affiliation(s)
- A Badiani
- Department of Psychology, Concordia University, Montréal, Québec, Canada
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28
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Nencini P, Valeri P, Pimpinella G. The α1-blocker dapiprazole inhibits diuresis but not drinking and feeding induced by U-50,488H. Brain Res Bull 1992; 29:401-5. [PMID: 1356599 DOI: 10.1016/0361-9230(92)90075-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To further explore the interaction between opiates and catecholamines in the control of water balance, we studied the effects of the alpha 1-adrenoceptor antagonist dapiprazole on the modifications in drinking and diuresis produced by U-50,488H (a selective kappa-opiate agonist), morphine, naloxone, and amphetamine in rats. Because animals were maintained in a free-feeding paradigm and water intake is also controlled by feeding (prandial drinking), food intake was also measured. At doses administered (3-6 mg/kg, IP), dapiprazole had no effect on basal food and water intake or on diuresis. Nor did it modify changes in feeding and drinking produced by U-50,488H, morphine, naloxone, and amphetamine. It did, however, antagonize the diuretic effect of both U-50,488H and amphetamine. In addition, suppression of diuresis was obtained by combining doses of dapiprazole and morphine or naloxone that were devoid of antidiuretic effects when administered independently. A further experiment showed that diuresis produced by water load was also prevented by dapiprazole. alpha 1-Adrenoceptors thus appear to play a role in the regulation of water balance in a condition of free access to water, inhibiting diuresis without affecting drinking.
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Affiliation(s)
- P Nencini
- Institute of Medical Pharmacology, University of Rome La Sapienza, Italy
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29
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Abstract
This paper, an examination of works published during 1990, is thirteenth in a series of our annual reviews of the research involving the behavioral, nonanalgesic, effects of the endogenous opiate peptides. The specific topics this year include stress; tolerance and dependence, eating; drinking; gastrointestinal, renal, and hepatic functions; mental illness; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; electrical-related activity; locomotor activity; sex, pregnancy, development, and aging; immunological responses; and other behavior.
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Affiliation(s)
- G A Olson
- Department of Psychology, University of New Orleans, LA 70148
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