1
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Orexin-1 receptor blockade differentially affects spatial and visual discrimination memory facilitation by intracranial self-stimulation. Neurobiol Learn Mem 2020; 169:107188. [PMID: 32061874 DOI: 10.1016/j.nlm.2020.107188] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 02/06/2020] [Accepted: 02/11/2020] [Indexed: 01/07/2023]
Abstract
Intracranial self-stimulation (ICSS) of the medial forebrain bundle is an effective treatment to facilitate memory. Performance in both explicit and implicit memory tasks has been improved by ICSS, and this treatment has even been capable of recovering loss of memory function due to lesions or old age. Several neurochemical systems have been studied in regard to their role in ICSS effects on memory, however the possible involvement of the orexinergic system in this facilitation has yet to be explored. The present study aims to examine the relationship between the OX1R and the facilitative effects of ICSS on two different types of memory tasks, both carried out in the Morris Water Maze: spatial and visual discrimination. Results show that the OX1R blockade, by intraventricular administration of SB-334867, partially negates the facilitating effect of ICSS on spatial memory, whereas it hinders ICSS facilitation of the discrimination task. However, ICSS treatment was capable of compensating for the severe detrimental effects of OX1R blockade on both memory paradigms. These results suggest different levels of involvement of the orexinergic system in the facilitation of memory by ICSS, depending on the memory task.
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2
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Role of orexin-1 and -2 receptors within the nucleus accumbens in the acquisition of sensitization to morphine in rats. Behav Brain Res 2019; 373:112090. [PMID: 31325517 DOI: 10.1016/j.bbr.2019.112090] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 07/14/2019] [Accepted: 07/16/2019] [Indexed: 12/18/2022]
Abstract
It has been reported that orexins A and B are involved in the mediation of drug reward. In addition, the nucleus accumbens (NAc) has an important role in the development of morphine-conditioned place preference (CPP) and morphine sensitization. In the present study, we aimed to evaluate the role of orexin receptors within the NAc in morphine sensitization using CPP paradigm. Adult male Wistar rats were used and were bilaterally implanted by two cannulae in the NAc. The animals received intra-accumbal administration of OX1 or OX2 receptor antagonists, SB-334867 (0.1, 1, and 10 nM/side) or TCS OX2 29 (2, 10, and 20 nM/side), 10 min before morphine injection during the sensitization period, during which the animals received repeated administration of morphine (5 mg/kg; s.c.) once daily for three days followed by 5 morphine injection-free days. Then the CPP paradigm was conducted for the evaluation of morphine rewarding properties by injecting a sub-threshold dose of morphine (0.5 mg/kg; s.c.). The results showed that bilateral administration of OX1 receptor antagonist into the NAc reduced acquisition of morphine sensitization in a dose-dependent manner, but OX2 receptor antagonist produced similar effect only at its highest dose, indicating that OX1 and OX2 receptors within the NAc are involved in the acquisition of morphine sensitization.
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Abstract
Narcolepsy is the most common neurological cause of chronic sleepiness. The discovery about 20 years ago that narcolepsy is caused by selective loss of the neurons producing orexins (also known as hypocretins) sparked great advances in the field. Here, we review the current understanding of how orexin neurons regulate sleep-wake behaviour and the consequences of the loss of orexin neurons. We also summarize the developing evidence that narcolepsy is an autoimmune disorder that may be caused by a T cell-mediated attack on the orexin neurons and explain how these new perspectives can inform better therapeutic approaches.
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Affiliation(s)
- Carrie E Mahoney
- Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
| | - Andrew Cogswell
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL, USA
| | - Igor J Koralnik
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL, USA
| | - Thomas E Scammell
- Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA.
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4
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Matzeu A, Martin-Fardon R. Drug Seeking and Relapse: New Evidence of a Role for Orexin and Dynorphin Co-transmission in the Paraventricular Nucleus of the Thalamus. Front Neurol 2018; 9:720. [PMID: 30210441 PMCID: PMC6121102 DOI: 10.3389/fneur.2018.00720] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Accepted: 08/08/2018] [Indexed: 01/19/2023] Open
Abstract
The long-lasting vulnerability to relapse remains the main challenge for the successful treatment of drug addiction. Neural systems that are involved in processing natural rewards and drugs of abuse overlap. However, neuroplasticity that is caused by drug exposure may be responsible for maladaptive, compulsive, and addictive behavior. The orexin (Orx) system participates in regulating numerous physiological processes, including energy metabolism, arousal, and feeding, and is recruited by drugs of abuse. The Orx system is differentially recruited by drugs and natural rewards. Specifically, we found that the Orx system is more engaged by drugs than by non-drugs, such as sweetened condensed milk (SCM) or a glucose saccharin solution (GSS), in an operant model of reward seeking. Although stimuli (S+) that are conditioned to cocaine (COC), ethanol, and SCM/GSS equally elicited reinstatement, Orx receptor blockade reversed conditioned reinstatement for drugs vs. non-drugs. Moreover, the hypothalamic recruitment of Orx cells was greater in rats that were tested with the COC S+ vs. SCM S+, indicating of a preferential role for the Orx system in perseverative, compulsive-like COC seeking and not behavior that is motivated by palatable food. Accumulating evidence indicates that the paraventricular nucleus of the thalamus (PVT), which receives major Orx projections, mediates drug-seeking behavior. All Orx neurons contain dynorphin (Dyn), and Orx and Dyn are co-released. In the VTA, they play opposing roles in reward and motivation. To fully understand the physiological and behavioral roles of Orx transmission in the PVT, one important consideration is that Orx neurons that project to the PVT may co-release Orx with another peptide, such as Dyn. The PVT expresses both Orx receptors and κ opioid receptors, suggesting that Orx and Dyn act in tandem when released in the PVT, in addition to the VTA. The present review discusses recent findings that suggest the maladaptive recruitment of Orx/Dyn-PVT neurotransmission by drugs of abuse vs. a highly palatable food reward.
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Affiliation(s)
- Alessandra Matzeu
- Department of Neuroscience, The Scripps Research Institute, La Jolla, CA, United States
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5
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Tyree SM, Borniger JC, de Lecea L. Hypocretin as a Hub for Arousal and Motivation. Front Neurol 2018; 9:413. [PMID: 29928253 PMCID: PMC5997825 DOI: 10.3389/fneur.2018.00413] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 05/18/2018] [Indexed: 01/01/2023] Open
Abstract
The lateral hypothalamus is comprised of a heterogeneous mix of neurons that serve to integrate and regulate sleep, feeding, stress, energy balance, reward, and motivated behavior. Within these populations, the hypocretin/orexin neurons are among the most well studied. Here, we provide an overview on how these neurons act as a central hub integrating sensory and physiological information to tune arousal and motivated behavior accordingly. We give special attention to their role in sleep-wake states and conditions of hyper-arousal, as is the case with stress-induced anxiety. We further discuss their roles in feeding, drug-seeking, and sexual behavior, which are all dependent on the motivational state of the animal. We further emphasize the application of powerful techniques, such as optogenetics, chemogenetics, and fiber photometry, to delineate the role these neurons play in lateral hypothalamic functions.
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Affiliation(s)
- Susan M Tyree
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA, United States
| | - Jeremy C Borniger
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA, United States
| | - Luis de Lecea
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA, United States
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6
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Steiner N, Rossetti C, Sakurai T, Yanagisawa M, de Lecea L, Magistretti PJ, Halfon O, Boutrel B. Hypocretin/orexin deficiency decreases cocaine abuse liability. Neuropharmacology 2018; 133:395-403. [PMID: 29454841 DOI: 10.1016/j.neuropharm.2018.02.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 01/12/2018] [Accepted: 02/12/2018] [Indexed: 12/13/2022]
Abstract
Compelling evidence indicates that hypocretin/orexin signaling regulates arousal, stress and reward-seeking behaviors. However, most studies on drug reward-related processes have so far described the effects of pharmacological blockers disrupting hypocretin/orexin transmission. We report here an extensive study on cocaine-related behaviors in hypocretin/orexin-deficient mice (KO) and their heterozygous (HET) and wildtype (WT) littermates. We evaluated behavioral sensitization following repeated administrations and preference for an environment repeatedly paired with cocaine injections (15 mg/kg). Mice were also trained to self-administer cocaine (0.5-1.5 mg/kg/infusion). Our observations show that whereas all mice exhibited quite similar responses to acute administration of cocaine, only Hcrt KO mice exhibited reduced cocaine-seeking behaviors following a period of abstinence or extinction, and reduced cocaine incubation craving. Further, if the present findings confirm that Hcrt deficient mice may display a hypoactive phenotype, possibly linked to a reduced alertness concomitant to a decreased exploration of their environment, hypocretin/orexin defiency did not cause any attentional deficit. We thus report that innate disruption of hypocretin/orexin signaling moderately alters cocaine reward but significantly reduces long-term affective dependence that may explain the lack of relapse for cocaine seeking seen in Hcrt KO mice. Overall, with blunted cocaine intake at the highest concentration and reduced responsiveness to cocaine cues after prolonged abstinence, our findings suggest that hypocretin deficient mice may display signs of resilience to cocaine addiction.
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Affiliation(s)
- Nadia Steiner
- Center for Psychiatric Neuroscience, Department of Psychiatry, Lausanne University Hospital, Switzerland
| | - Clara Rossetti
- Center for Psychiatric Neuroscience, Department of Psychiatry, Lausanne University Hospital, Switzerland
| | - Takeshi Sakurai
- Department of Molecular Neuroscience and Integrative Physiology, Faculty of Medicine, Kanazawa University, Japan; International Institute for Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Japan
| | - Masashi Yanagisawa
- International Institute for Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Japan
| | - Luis de Lecea
- Dept. of Psychiatry and Behavioral Sciences, Stanford University, USA
| | - Pierre J Magistretti
- Center for Psychiatric Neuroscience, Department of Psychiatry, Lausanne University Hospital, Switzerland
| | - Olivier Halfon
- Division of Adolescent and Child Psychiatry, Department of Psychiatry, Lausanne University Hospital, Switzerland
| | - Benjamin Boutrel
- Center for Psychiatric Neuroscience, Department of Psychiatry, Lausanne University Hospital, Switzerland; Division of Adolescent and Child Psychiatry, Department of Psychiatry, Lausanne University Hospital, Switzerland.
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7
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Barson JR, Leibowitz SF. Orexin/Hypocretin System: Role in Food and Drug Overconsumption. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2017; 136:199-237. [PMID: 29056152 DOI: 10.1016/bs.irn.2017.06.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The neuropeptide orexin/hypocretin (OX), while largely transcribed within the hypothalamus, is released throughout the brain to affect complex behaviors. Primarily through the hypothalamus itself, OX homeostatically regulates adaptive behaviors needed for survival, including food intake, sleep-wake regulation, mating, and maternal behavior. However, through extrahypothalamic limbic brain regions, OX promotes seeking and intake of rewarding substances of abuse, like palatable food, alcohol, nicotine, and cocaine. This neuropeptide, in turn, is stimulated by the intake of or early life exposure to these substances, forming a nonhomeostatic, positive feedback loop. The specific OX receptor involved in these behaviors, whether adaptive behavior or substance seeking and intake, is dependent on the particular brain region that contributes to them. Thus, we propose that, while the primary function of OX is to maintain arousal for the performance of adaptive behaviors, this neuropeptide system is readily co-opted by rewarding substances that involve positive feedback, ultimately promoting their abuse.
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Affiliation(s)
- Jessica R Barson
- Drexel University College of Medicine, Philadelphia, PA, United States
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8
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James MH, Mahler SV, Moorman DE, Aston-Jones G. A Decade of Orexin/Hypocretin and Addiction: Where Are We Now? Curr Top Behav Neurosci 2017; 33:247-281. [PMID: 28012090 PMCID: PMC5799809 DOI: 10.1007/7854_2016_57] [Citation(s) in RCA: 122] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
One decade ago, our laboratory provided the first direct evidence linking orexin/hypocretin signaling with drug seeking by showing that activation of these neurons promotes conditioned morphine-seeking behavior. In the years since, contributions from many investigators have revealed roles for orexins in addiction for all drugs of abuse tested, but only under select circumstances. We recently proposed that orexins play a fundamentally unified role in coordinating "motivational activation" under numerous behavioral conditions, and here we unpack this hypothesis as it applies to drug addiction. We describe evidence collected over the past 10 years that elaborates the role of orexin in drug seeking under circumstances where high levels of effort are required to obtain the drug, or when motivation for drug reward is augmented by the presence of external stimuli like drug-associated cues/contexts or stressors. Evidence from studies using traditional self-administration and reinstatement models, as well as behavioral economic analyses of drug demand elasticity, clearly delineates a role for orexin in modulating motivational, rather than the primary reinforcing aspects of drug reward. We also discuss the anatomical interconnectedness of the orexin system with wider motivation and reward circuits, with a particular focus on how orexin modulates prefrontal and other glutamatergic inputs onto ventral tegmental area dopamine neurons. Last, we look ahead to the next decade of the research in this area, highlighting the recent FDA approval of the dual orexin receptor antagonist suvorexant (Belsomra®) for the treatment of insomnia as a promising sign of the potential clinical utility of orexin-based therapies for the treatment of addiction.
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Affiliation(s)
- Morgan H James
- Brain Health Institute, Rutgers University/Rutgers Biomedical and Health Sciences, Piscataway, NJ, 08854, USA
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC, 2337, Australia
| | - Stephen V Mahler
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA, 92967, USA
| | - David E Moorman
- Department of Psychological and Brain Sciences & Neuroscience and Behavior Graduate Program, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Gary Aston-Jones
- Brain Health Institute, Rutgers University/Rutgers Biomedical and Health Sciences, Piscataway, NJ, 08854, USA.
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9
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Valdivia S, Cornejo MP, Reynaldo M, De Francesco PN, Perello M. Escalation in high fat intake in a binge eating model differentially engages dopamine neurons of the ventral tegmental area and requires ghrelin signaling. Psychoneuroendocrinology 2015; 60:206-16. [PMID: 26186250 DOI: 10.1016/j.psyneuen.2015.06.018] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Revised: 06/02/2015] [Accepted: 06/29/2015] [Indexed: 10/23/2022]
Abstract
Binge eating is a behavior observed in a variety of human eating disorders. Ad libitum fed rodents daily and time-limited exposed to a high-fat diet (HFD) display robust binge eating events that gradually escalate over the initial accesses. Intake escalation is proposed to be part of the transition from a controlled to a compulsive or loss of control behavior. Here, we used a combination of behavioral and neuroanatomical studies in mice daily and time-limited exposed to HFD to determine the neuronal brain targets that are activated--as indicated by the marker of cellular activation c-Fos--under these circumstances. Also, we used pharmacologically or genetically manipulated mice to study the role of orexin or ghrelin signaling, respectively, in the modulation of this behavior. We found that four daily and time-limited accesses to HFD induce: (i) a robust hyperphagia with an escalating profile, (ii) an activation of different sub-populations of the ventral tegmental area dopamine neurons and accumbens neurons that is, in general, more pronounced than the activation observed after a single HFD consumption event, and (iii) an activation of the hypothalamic orexin neurons, although orexin signaling blockage fails to affect escalation of HFD intake. In addition, we found that ghrelin receptor-deficient mice fail to both escalate the HFD consumption over the successive days of exposure and fully induce activation of the mesolimbic pathway in response to HFD consumption. Current data suggest that the escalation in high fat intake during repeated accesses differentially engages dopamine neurons of the ventral tegmental area and requires ghrelin signaling.
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Affiliation(s)
- Spring Valdivia
- Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE-CONICET/CICPBA), La Plata, Argentina
| | - María P Cornejo
- Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE-CONICET/CICPBA), La Plata, Argentina
| | - Mirta Reynaldo
- Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE-CONICET/CICPBA), La Plata, Argentina
| | - Pablo N De Francesco
- Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE-CONICET/CICPBA), La Plata, Argentina
| | - Mario Perello
- Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE-CONICET/CICPBA), La Plata, Argentina.
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10
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Hypocretin (orexin) facilitates reward by attenuating the antireward effects of its cotransmitter dynorphin in ventral tegmental area. Proc Natl Acad Sci U S A 2014; 111:E1648-55. [PMID: 24706819 DOI: 10.1073/pnas.1315542111] [Citation(s) in RCA: 186] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Hypocretin (orexin) and dynorphin are neuropeptides with opposing actions on motivated behavior. Orexin is implicated in states of arousal and reward, whereas dynorphin is implicated in depressive-like states. We show that, despite their opposing actions, these peptides are packaged in the same synaptic vesicles within the hypothalamus. Disruption of orexin function blunts the rewarding effects of lateral hypothalamic (LH) stimulation, eliminates cocaine-induced impulsivity, and reduces cocaine self-administration. Concomitant disruption of dynorphin function reverses these behavioral changes. We also show that orexin and dynorphin have opposing actions on excitability of ventral tegmental area (VTA) dopamine neurons, a prominent target of orexin-containing neurons, and that intra-VTA orexin antagonism causes decreases in cocaine self-administration and LH self-stimulation that are reversed by dynorphin antagonism. Our findings identify a unique cellular process by which orexin can occlude the reward threshold-elevating effects of coreleased dynorphin and thereby act in a permissive fashion to facilitate reward.
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11
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Boutrel B, Steiner N, Halfon O. The hypocretins and the reward function: what have we learned so far? Front Behav Neurosci 2013; 7:59. [PMID: 23781178 PMCID: PMC3680710 DOI: 10.3389/fnbeh.2013.00059] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Accepted: 05/19/2013] [Indexed: 01/15/2023] Open
Abstract
A general consensus acknowledges that drug consumption (including alcohol, tobacco, and illicit drugs) constitutes the leading cause of preventable death worldwide. But the global burden of drug abuse extends the mortality statistics. Indeed, the comorbid long-term debilitating effects of the disease also significantly deteriorate the quality of life of individuals suffering from addiction disorders. Despite the large body of evidence delineating the cellular and molecular adaptations induced by chronic drug consumption, the brain mechanisms responsible for drug craving and relapse remain insufficiently understood, and even the most recent developments in the field have not brought significant improvement in the management of drug dependence. Though, recent preclinical evidence suggests that disrupting the hypocretin (orexin) system may serve as an anticraving medication therapy. Here, we discuss how the hypocretins, which orchestrate normal wakefulness, metabolic health and the execution of goal-oriented behaviors, may be compromised and contribute to elicit compulsive drug seeking. We propose an overview on the most recent studies demonstrating an important role for the hypocretin neuropeptide system in the regulation of drug reward and the prevention of drug relapse, and we question the relevance of disrupting the hypocretin system to alleviate symptoms of drug addiction.
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Affiliation(s)
- Benjamin Boutrel
- Department of Psychiatry, Center for Psychiatric Neuroscience, Lausanne University Hospital Lausanne, Switzerland ; Department of Psychiatry, Division of Child and Adolescent Psychiatry, Lausanne University Hospital Lausanne, Switzerland
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12
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α GABAA subunit-orexin receptor interactions activate learning/motivational pathways in the goldfish. Behav Brain Res 2012; 234:349-56. [DOI: 10.1016/j.bbr.2012.07.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 07/04/2012] [Accepted: 07/08/2012] [Indexed: 10/28/2022]
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13
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Hollander JA, Pham D, Fowler CD, Kenny PJ. Hypocretin-1 receptors regulate the reinforcing and reward-enhancing effects of cocaine: pharmacological and behavioral genetics evidence. Front Behav Neurosci 2012; 6:47. [PMID: 22837742 PMCID: PMC3402880 DOI: 10.3389/fnbeh.2012.00047] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2012] [Accepted: 07/05/2012] [Indexed: 11/13/2022] Open
Abstract
Considerable evidence suggests that transmission at hypocretin-1 (orexin-1) receptors (Hcrt-R1) plays an important role in the reinstatement of extinguished cocaine-seeking behaviors in rodents. However, far less is known about the role for hypocretin transmission in regulating ongoing cocaine-taking behavior. Here, we investigated the effects of the selective Hcrt-R1 antagonist SB-334867 on cocaine intake, as measured by intravenous (IV) cocaine self-administration in rats. The stimulatory effects of cocaine on brain reward systems contribute to the establishment and maintenance of cocaine-taking behaviors. Therefore, we also assessed the effects of SB-334867 on the reward-enhancing properties of cocaine, as measured by cocaine-induced lowering of intracranial self-stimulation (ICSS) thresholds. Finally, to definitively establish a role for Hcrt-R1 in regulating cocaine intake, we assessed IV cocaine self-administration in Hcrt-R1 knockout mice. We found that SB-334867 (1-4 mg/kg) dose-dependently decreased cocaine (0.5 mg/kg/infusion) self-administration in rats but did not alter responding for food rewards under the same schedule of reinforcement. This suggests that SB-334867 decreased cocaine reinforcement without negatively impacting operant performance. SB-334867 (1-4 mg/kg) also dose-dependently attenuated the stimulatory effects of cocaine (10 mg/kg) on brain reward systems, as measured by reversal of cocaine-induced lowering of ICSS thresholds in rats. Finally, we found that Hcrt-R1 knockout mice self-administered far less cocaine than wildtype mice across the entire dose-response function. These data demonstrate that Hcrt-R1 play an important role in regulating the reinforcing and reward-enhancing properties of cocaine and suggest that hypocretin transmission is likely essential for establishing and maintaining the cocaine habit in human addicts.
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Affiliation(s)
- Jonathan A Hollander
- Laboratory of Behavioral and Molecular Neuroscience, Department of Molecular Therapeutics, The Scripps Research Institute, Jupiter FL, USA
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14
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Mahler SV, Smith RJ, Moorman DE, Sartor GC, Aston-Jones G. Multiple roles for orexin/hypocretin in addiction. PROGRESS IN BRAIN RESEARCH 2012; 198:79-121. [PMID: 22813971 PMCID: PMC3643893 DOI: 10.1016/b978-0-444-59489-1.00007-0] [Citation(s) in RCA: 154] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Orexins/hypocretins are hypothalamic peptides involved in arousal and wakefulness, but also play a critical role in drug addiction and reward-related behaviors. Here, we review the roles played by orexins in a variety of animal models of drug addiction, emphasizing both commonalities and differences for orexin's involvement in seeking of the major classes of abused drugs, as well as food. One common theme that emerges is an involvement of orexins in drug seeking triggered by external stimuli (e.g., cues, contexts or stressors). We also discuss the functional neuronal circuits in which orexins are embedded, and how these circuits mediate addiction-related behaviors, with particular focus on the role of orexin and glutamate interactions within the ventral tegmental area. Finally, we attempt to contextualize the role of orexins in reward by discussing ways in which these peptides, expressed in only a few thousand neurons in the brain, can have such wide-ranging effects on behavior.
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Affiliation(s)
- Stephen V. Mahler
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC, USA
| | - Rachel J. Smith
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC, USA
| | - David E. Moorman
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC, USA
| | - Gregory C. Sartor
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC, USA
| | - Gary Aston-Jones
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC, USA
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