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Sadee W. Ligand-Free Signaling of G-Protein-Coupled Receptors: Physiology, Pharmacology, and Genetics. Molecules 2023; 28:6375. [PMID: 37687205 PMCID: PMC10489045 DOI: 10.3390/molecules28176375] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Revised: 08/28/2023] [Accepted: 08/30/2023] [Indexed: 09/10/2023] Open
Abstract
G-protein-coupled receptors (GPCRs) are ubiquitous sensors and regulators of cellular functions. Each GPCR exists in complex aggregates with multiple resting and active conformations. Designed to detect weak stimuli, GPCRs can also activate spontaneously, resulting in basal ligand-free signaling. Agonists trigger a cascade of events leading to an activated agonist-receptor G-protein complex with high agonist affinity. However, the ensuing signaling process can further remodel the receptor complex to reduce agonist affinity, causing rapid ligand dissociation. The acutely activated ligand-free receptor can continue signaling, as proposed for rhodopsin and μ opioid receptors, resulting in robust receptor activation at low agonist occupancy with enhanced agonist potency. Continued receptor stimulation can further modify the receptor complex, regulating sustained ligand-free signaling-proposed to play a role in opioid dependence. Basal, acutely agonist-triggered, and sustained elevated ligand-free signaling could each have distinct functions, reflecting multi-state conformations of GPCRs. This review addresses basal and stimulus-activated ligand-free signaling, its regulation, genetic factors, and pharmacological implications, focusing on opioid and serotonin receptors, and the growth hormone secretagogue receptor (GHSR). The hypothesis is proposed that ligand-free signaling of 5-HT2A receptors mediate therapeutic effects of psychedelic drugs. Research avenues are suggested to close the gaps in our knowledge of ligand-free GPCR signaling.
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Affiliation(s)
- Wolfgang Sadee
- Cancer Biology and Genetics, College of Medicine, The Ohio State University, Columbus, OH 43210, USA;
- Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158, USA
- Aether Therapeutics Inc., Austin, TX 78756, USA
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2
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Zia FZ, Baumann MH, Belouin SJ, Dworkin RH, Ghauri MH, Hendricks PS, Henningfield JE, Lanier RK, Ross S, Berger A. Are psychedelic medicines the reset for chronic pain? Preliminary findings and research needs. Neuropharmacology 2023; 233:109528. [PMID: 37015315 DOI: 10.1016/j.neuropharm.2023.109528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 03/24/2023] [Accepted: 03/28/2023] [Indexed: 04/06/2023]
Abstract
Chronic pain is a leading cause of disability, reduced productivity, healthcare seeking, and a contributor to opioid overdose in the United States. For many people, pain can be satisfactorily managed by existing medicines and comprehensive psychosocial treatments. For others, available treatments are either ineffective or not acceptable due to side effects and concerns about risks. Preliminary evidence suggests that some psychedelics may be effective for certain types of pain and/or improved quality of life with increased functionality and reduced disability and distress in people whose pain may never be completely relieved. Efficacy in these quality-of-life related outcomes would be consistent with the "reset in thinking" about chronic pain management increasingly called for as a more realistic goal for some people than complete elimination of pain. This commentary summarizes the rationale for conducting more basic research and clinical trials to further explore the potential for psychedelics in chronic pain management. And, if shown to be effective, to determine whether the effects of psychedelics are primarily due to direct antinociceptive or anti-inflammatory mechanisms, or via increased tolerability, acceptance, and sense of spirituality, that appear to at least partially mediate the therapeutic effects of psychedelics observed in psychiatric disorders such as major depression. This commentary represents a collaboration of clinical and more basic scientists examining these issues and developing recommendations for research ranging from neuropharmacology to the biopsychosocial treatment factors that appear to be as important in pain management as in depression and other disorders in which psychedelic medicines are under development.
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Affiliation(s)
- Farah Z Zia
- Department of Health and Human Services, National Institutes of Health, National Cancer Institute, Division of Cancer Treatment and Diagnosis, OCCAM 9609 Medical Center Drive, Suite 1W-706, Rockville, MD, 20850, USA.
| | - Michael H Baumann
- Designer Drug Research Unit (DDRU) Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 333 Cassell Drive, Suite 4400, Baltimore, MD, USA
| | - Sean J Belouin
- United States Public Health Service, Germantown, MD, USA; Substance Abuse and Mental Health Services Administration (SAMHSA), Rockville, MD, USA
| | - Robert H Dworkin
- University of Rochester School of Medicine and Dentistry, Rochester, NY, USA; Department of Anesthesiology, Critical Care and Pain Management, Hospital for Special Surgery Research Institute, New York, NY, USA
| | - Majid H Ghauri
- Spine and Pain Clinics of North America, Fair Oaks Medical Building, 4001 Fair Ridge Drive, Suite 202, Fairfax, VA, USA; University of Virginia (UVA) Health System, Departments of Anesthesiology and Pain Management, 1215 Lee Street, Charlottesville, VA, 22903, USA
| | - Peter S Hendricks
- Department of Health Behavior, School of Public Health, University of Alabama at Birmingham, 1665 University Blvd Birmingham, AL 3522, USA
| | - Jack E Henningfield
- PineyAssociates, Inc, 4800 Montgomery Lane, Suite 400, Bethesda, MD, USA; Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Ryan K Lanier
- PineyAssociates, Inc, 4800 Montgomery Lane, Suite 400, Bethesda, MD, USA
| | - Stephen Ross
- NYU Langone Center for Psychedelic Medicine, NYU Grossman School of Medicine, One Park Ave, New York, NY, 10016, USA
| | - Ann Berger
- Pain and Palliative Care, National Institutes of Health Clinical Center, Bethesda, MD, USA
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Glynos NG, Pierce J, Davis AK, McAfee J, Boehnke KF. Knowledge, Perceptions, and Use of Psychedelics among Individuals with Fibromyalgia. J Psychoactive Drugs 2023; 55:73-84. [PMID: 35001856 DOI: 10.1080/02791072.2021.2022817] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Fibromyalgia (FM) is a difficult to treat chronic pain condition for which there is strong interest in alternative treatments. There is growing interest in the potential of psychedelic substances (e.g., psilocybin) in conjunction with psychotherapy to treat chronic pain. Via a cross-sectional, anonymous, online survey, we aimed to characterize knowledge, perceptions, and past use of serotonergic ("classic") and non-serotonergic psychedelics among a population of individuals with FM, and to investigate interest in psychedelic-based FM treatments. Among a North American population of 354 participants with FM, 29.9% reported past use of a psychedelic, with lysergic acid diethylamide (LSD) and psilocybin mushrooms being most commonly used. Perceptions of benefit from psychedelic use were generally neutral (59.4%) or positive (36.8%), with <3% reporting negative impacts on overall health or pain symptoms. Among 12 participants who used psychedelics with intentions of treating chronic pain, 11 reported improved symptoms. Regardless of past use, the majority of participants believed that psychedelics have potential for chronic pain treatments and would be willing to participate in a psychedelic-based clinical trial for their pain. These findings support the need for additional studies to understand the potential and effectiveness of psychedelic substances in managing FM symptoms.
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Affiliation(s)
- Nicolas G Glynos
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, USA.,Center for Consciousness Science, University of Michigan, Ann Arbor, MI, USA
| | - Jennifer Pierce
- Anesthesiology Department, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Alan K Davis
- College of Social Work and Department of Psychiatry, Ohio State University, Columbus, OH, USA.,Center for Psychedelic and Consciousness Research, Johns Hopkins University, Baltimore, MD, USA
| | - Jenna McAfee
- Anesthesiology Department, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Kevin F Boehnke
- Anesthesiology Department, University of Michigan Medical School, Ann Arbor, MI, USA
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4
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Buchborn T, Lyons T, Song C, Feilding A, Knöpfel T. The serotonin 2A receptor agonist 25CN-NBOH increases murine heart rate and neck-arterial blood flow in a temperature-dependent manner. J Psychopharmacol 2020; 34:786-794. [PMID: 32048564 PMCID: PMC7488829 DOI: 10.1177/0269881120903465] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
BACKGROUND Serotonin 2A receptors, the molecular target of psychedelics, are expressed by neuronal and vascular cells, both of which might contribute to brain haemodynamic characteristics for the psychedelic state. AIM Aiming for a systemic understanding of psychedelic vasoactivity, here we investigated the effect of N-(2-hydroxybenzyl)-2,5-dimethoxy-4-cyanophenylethylamine - a new-generation agonist with superior serotonin 2A receptor selectivity - on brain-supplying neck-arterial blood flow. METHODS We recorded core body temperature and employed non-invasive, collar-sensor based pulse oximetry in anesthetised mice to extract parameters of local blood perfusion, oxygen saturation, heart and respiration rate. Hypothesising an overlap between serotonergic pulse- and thermoregulation, recordings were done under physiological and elevated pad temperatures. RESULTS N-(2-hydroxybenzyl)-2,5-dimethoxy-4-cyanophenylethylamine (1.5 mg/kg, subcutaneous) significantly increased the frequency of heart beats accompanied by a slight elevation of neck-arterial blood flow. Increasing the animal-supporting heat-pad temperature from 37°C to 41°C enhanced the drug's effect on blood flow while counteracting tachycardia. Additionally, N-(2-hydroxybenzyl)-2,5-dimethoxy-4-cyanophenylethylamine promoted bradypnea, which, like tachycardia, quickly reversed at the elevated pad temperature. The interrelatedness of N-(2-hydroxybenzyl)-2,5-dimethoxy-4-cyanophenylethylamine's respiro-cardiovascular effects and thermoregulation was further corroborated by the drug selectively increasing the core body temperature at the elevated pad temperature. Arterial oxygen saturation was not affected by N-(2-hydroxybenzyl)-2,5-dimethoxy-4-cyanophenylethylamine at either temperature. CONCLUSIONS Our findings imply that selective serotonin 2A receptor activation modulates systemic cardiovascular functioning in orchestration with thermoregulation and with immediate relevance to brain-imminent neck (most likely carotid) arteries. As carotid branching is a critical last hub to channel cardiovascular output to or away from the brain, our results might have implications for the brain haemodynamics associated with psychedelia.
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Affiliation(s)
- Tobias Buchborn
- Laboratory for Neuronal Circuit Dynamics, Department of Medicine, Imperial College, London, UK,Centre for Psychedelic Research, Department of Medicine, Imperial College, London, UK,Tobias Buchborn, Laboratory for Neuronal Circuit Dynamics, Department of Medicine, Imperial College, Du Cane Road, Burlington Danes, London, W12 0NN, UK.
| | - Taylor Lyons
- Laboratory for Neuronal Circuit Dynamics, Department of Medicine, Imperial College, London, UK,Centre for Psychedelic Research, Department of Medicine, Imperial College, London, UK
| | - Chenchen Song
- Laboratory for Neuronal Circuit Dynamics, Department of Medicine, Imperial College, London, UK
| | | | - Thomas Knöpfel
- Laboratory for Neuronal Circuit Dynamics, Department of Medicine, Imperial College, London, UK,Centre for Neurotechnology, Institute of Biomedical Engineering, Imperial College, London, UK
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5
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Castellanos JP, Woolley C, Bruno KA, Zeidan F, Halberstadt A, Furnish T. Chronic pain and psychedelics: a review and proposed mechanism of action. Reg Anesth Pain Med 2020; 45:486-494. [DOI: 10.1136/rapm-2020-101273] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 04/01/2020] [Accepted: 04/06/2020] [Indexed: 12/22/2022]
Abstract
The development of chronic pain is a complex mechanism that is still not fully understood. Multiple somatic and visceral afferent pain signals, when experienced over time, cause a strengthening of certain neural circuitry through peripheral and central sensitization, resulting in the physical and emotional perceptual chronic pain experience. The mind-altering qualities of psychedelics have been attributed, through serotonin 2A (5-HT2A) receptor agonism, to ‘reset’ areas of functional connectivity (FC) in the brain that play prominent roles in many central neuropathic states. Psychedelic substances have a generally favorable safety profile, especially when compared with opioid analgesics. Clinical evidence to date for their use for chronic pain is limited; however, several studies and reports over the past 50 years have shown potential analgesic benefit in cancer pain, phantom limb pain and cluster headache. While the mechanisms by which the classic psychedelics may provide analgesia are not clear, several possibilities exist given the similarity between 5-HT2A activation pathways of psychedelics and the nociceptive modulation pathways in humans. Additionally, the alterations in FC seen with psychedelic use suggest a way that these agents could help reverse the changes in neural connections seen in chronic pain states. Given the current state of the opioid epidemic and limited efficacy of non-opioid analgesics, it is time to consider further research on psychedelics as analgesics in order to improve the lives of patients with chronic pain conditions.
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Serotonin 2A receptors are a stress response system: implications for post-traumatic stress disorder. Behav Pharmacol 2020; 30:151-162. [PMID: 30632995 DOI: 10.1097/fbp.0000000000000459] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Serotonin, one of the first neurotransmitters to be identified, is an evolutionarily old molecule that is highly conserved across the animal kingdom, and widely used throughout the brain. Despite this, ascribing a specific set of functions to brain serotonin and its receptors has been difficult and controversial. The 2A subtype of serotonin receptors (5-HT2A receptor) is the major excitatory serotonin receptor in the brain and has been linked to the effects of drugs that produce profound sensory and cognitive changes. Numerous studies have shown that this receptor is upregulated by a broad variety of stressors, and have related 5-HT2A receptor function to associative learning. This review proposes that stress, particularly stress related to danger and existential threats, increases the expression and function of 5-HT2A receptors. It is argued that this is a neurobiological adaptation to promote learning and avoidance of danger in the future. Upregulation of 5-HT2A receptors during stressful events forms associations that tune the brain to environmental cues that signal danger. It is speculated that life-threatening situations may activate this system and contribute to the symptoms associated with post-traumatic stress disorder (PTSD). 3,4-Methylenedioxymethamphetamine, which activates 5-HT2A receptors, has been successful in the treatment of PTSD and has recently achieved status as a breakthrough therapy. An argument is presented that 3,4-methylenedioxymethamphetamine may paradoxically act through these same 5-HT2A receptors to ameliorate the symptoms of PTSD. The central thematic contention is that a key role of serotonin may be to function as a stress detection and response system.
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7
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Effects of the synthetic psychedelic 2,5-dimethoxy-4-iodoamphetamine (DOI) on ethanol consumption and place conditioning in male mice. Psychopharmacology (Berl) 2019; 236:3567-3578. [PMID: 31309240 PMCID: PMC6895420 DOI: 10.1007/s00213-019-05328-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Accepted: 07/08/2019] [Indexed: 12/27/2022]
Abstract
RATIONALE Approximately 20 million adults in the USA have an alcohol use disorder (AUD). There are clinical and preclinical data suggesting that psychedelics may have benefits for AUD. OBJECTIVE To investigate the effects of the synthetic psychedelic 2,5-dimethoxy-4-iodoamphetamine (DOI) on the behavioral effects of ethanol. METHODS The effects of DOI were examined using ethanol-induced place conditioning (1.8 g/kg ethanol) and 2-bottle choice ethanol drinking (20% v/v), using a dose of DOI (3 mg/kg) that produced the maximal response in the serotonin 2A (5-HT2A) receptor-dependent head-twitch assay. Interactions between DOI and ethanol (3 g/kg) were examined using the ethanol-induced loss of righting reflex procedure and blood-ethanol analysis. To examine additional mechanisms by which psychedelics may interact with ethanol, we determined whether DOI reverses ethanol-induced nitric oxide release in macrophages, a marker of inflammation. RESULTS DOI significantly attenuated ethanol-induced place conditioning and ethanol drinking. DOI-induced suppression of alcohol drinking depended upon 5-HT2A receptors, was selective for alcohol over water, and was selective for high alcohol-preferring subjects. DOI had no apparent pharmacokinetic interactions with ethanol, and DOI reduced ethanol-induced nitric oxide release. CONCLUSIONS Our findings demonstrate that DOI blocks ethanol place conditioning and selectively reduces voluntary ethanol consumption. This may be related to modulation of the effects of ethanol in the reward circuitry of the brain, ethanol-induced neuroinflammation, or a combination of both. Additional studies to elucidate the mechanisms through which psychedelics attenuate the effects of ethanol would inform the pathophysiology of AUD and potentially provide new treatment options.
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Benvenga MJ, Chaney SF, Baez M, Britton TC, Hornback WJ, Monn JA, Marek GJ. Metabotropic Glutamate 2 Receptors Play a Key Role in Modulating Head Twitches Induced by a Serotonergic Hallucinogen in Mice. Front Pharmacol 2018; 9:208. [PMID: 29599719 PMCID: PMC5862811 DOI: 10.3389/fphar.2018.00208] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 02/23/2018] [Indexed: 11/29/2022] Open
Abstract
There is substantial evidence that glutamate can modulate the effects of 5-hydroxytryptamine2A (5-HT2A) receptor activation through stimulation of metabotropic glutamate2/3 (mGlu2/3) receptors in the prefrontal cortex. Here we show that constitutive deletion of the mGlu2 gene profoundly attenuates an effect of 5-HT2A receptor activation using the mouse head twitch response (HTR). MGlu2 and mGlu3 receptor knockout (KO) as well as age-matched ICR (CD-1) wild type (WT) mice were administered (±)1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) and observed for head twitch activity. DOI failed to produce significant head twitches in mGlu2 receptor KO mice at a dose 10-fold higher than the peak effective dose in WT or mGlu3 receptor KO mice. In addition, the mGlu2/3 receptor agonist LY379268, and the mGlu2 receptor positive allosteric modulator (PAM) CBiPES, potently blocked the HTR to DOI in WT and mGlu3 receptor KO mice. Conversely, the mGlu2/3 receptor antagonist LY341495 (10 mg/kg) increased the HTR produced by DOI (3 mg/kg) in mGlu3 receptor KO mice. Finally, the mGlu2 receptor potentiator CBiPES was able to attenuate the increase in the HTR produced by LY341495 in mGlu3 receptor KO mice. Taken together, all of these results are consistent with the hypothesis that that DOI-induced head twitches are modulated by mGlu2 receptor activation. These results also are in keeping with a critical autoreceptor function for mGlu2 receptors in the prefrontal cortex with differential effects of acute vs. chronic perturbation (e.g., constitutive mGlu2 receptor KO mice). The robust attenuation of DOI-induced head twitches in the mGlu2 receptor KO mice appears to reflect the critical role of glutamate in ongoing regulation of 5-HT2A receptors in the prefrontal cortex. Future experiments with inducible knockouts for the mGlu2 receptor and/or selective mGlu3 receptor agonists/PAMs/antagonists could provide an important tools in understanding glutamatergic modulation of prefrontal cortical 5-HT2A receptor function.
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Affiliation(s)
- Mark J Benvenga
- Neuroscience Discovery Research, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, United States.,Lilly Corporate Center, Eli Lilly and Company, Indianapolis, IN, United States
| | - Stephen F Chaney
- Neuroscience Discovery Research, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, United States
| | - Melvyn Baez
- Neuroscience Discovery Research, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, United States
| | - Thomas C Britton
- Discovery Chemistry Research, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, United States
| | - William J Hornback
- Discovery Chemistry Research, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, United States
| | - James A Monn
- Discovery Chemistry Research, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, United States
| | - Gerard J Marek
- Neuroscience Discovery Research, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, United States
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9
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Schindler EAD, Wallace RM, Sloshower JA, D'Souza DC. Neuroendocrine Associations Underlying the Persistent Therapeutic Effects of Classic Serotonergic Psychedelics. Front Pharmacol 2018; 9:177. [PMID: 29545753 PMCID: PMC5838010 DOI: 10.3389/fphar.2018.00177] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 02/16/2018] [Indexed: 12/12/2022] Open
Abstract
Recent reports on the effects of psychedelic-assisted therapies for mood disorders and addiction, as well as the effects of psychedelics in the treatment of cluster headache, have demonstrated promising therapeutic results. In addition, the beneficial effects appear to persist well after limited exposure to the drugs, making them particularly appealing as treatments for chronic neuropsychiatric and headache disorders. Understanding the basis of the long-lasting effects, however, will be critical for the continued use and development of this drug class. Several mechanisms, including biological and psychological ones, have been suggested to explain the long-lasting effects of psychedelics. Actions on the neuroendocrine system are some such mechanisms that warrant further investigation in the study of persisting psychedelic effects. In this report, we review certain structural and functional neuroendocrinological pathologies associated with neuropsychiatric disorders and cluster headache. We then review the effects that psychedelic drugs have on those systems and provide preliminary support for potential long-term effects. The circadian biology of cluster headache is of particular relevance in this area. We also discuss methodologic considerations for future investigations of neuroendocrine system involvement in the therapeutic benefits of psychedelic drugs.
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Affiliation(s)
- Emmanuelle A D Schindler
- Department of Neurology, Yale School of Medicine, New Haven, CT, United States.,Department of Neurology, VA Connecticut Healthcare System, West Haven, CT, United States
| | - Ryan M Wallace
- Department of Psychiatry, Yale School of Medicine, New Haven, CT, United States
| | - Jordan A Sloshower
- Department of Psychiatry, Yale School of Medicine, New Haven, CT, United States.,Department of Psychiatry, VA Connecticut Healthcare System, West Haven, CT, United States
| | - Deepak C D'Souza
- Department of Psychiatry, Yale School of Medicine, New Haven, CT, United States.,Department of Psychiatry, VA Connecticut Healthcare System, West Haven, CT, United States
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The renaissance in psychedelic research: What do preclinical models have to offer. PROGRESS IN BRAIN RESEARCH 2018; 242:25-67. [DOI: 10.1016/bs.pbr.2018.08.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Pisano VD, Putnam NP, Kramer HM, Franciotti KJ, Halpern JH, Holden SC. The association of psychedelic use and opioid use disorders among illicit users in the United States. J Psychopharmacol 2017; 31:606-613. [PMID: 28196428 DOI: 10.1177/0269881117691453] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
BACKGROUND Preliminary studies show psychedelic compounds administered with psychotherapy are potentially effective and durable substance misuse interventions. However, little is known about the association between psychedelic use and substance misuse in the general population. This study investigated the association between psychedelic use and past year opioid use disorders within illicit opioid users. METHODS While controlling for socio-demographic covariates and the use of other substances, the relationship between classic psychedelic use and past year opioid use disorders was analyzed within 44,000 illicit opioid users who completed the National Survey on Drug Use and Health from 2008 to 2013. RESULTS Among respondents with a history of illicit opioid use, psychedelic drug use is associated with 27% reduced risk of past year opioid dependence (weighted risk ratio = 0.73 (0.60-0.89) p = 0.002) and 40% reduced risk of past year opioid abuse (weighted risk ratio = 0.60 (0.41-0.86) p = 0.006). Other than marijuana use, which was associated with 55% reduced risk of past year opioid abuse (weighted risk ratio = 0.45 (0.30-0.66) p < 0.001), no other illicit drug was associated with reduced risk of past year opioid dependence or abuse. CONCLUSION Experience with psychedelic drugs is associated with decreased risk of opioid abuse and dependence. Conversely, other illicit drug use history is largely associated with increased risk of opioid abuse and dependence. These findings suggest that psychedelics are associated with positive psychological characteristics and are consistent with prior reports suggesting efficacy in treatment of substance use disorders.
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Affiliation(s)
- Vincent D Pisano
- 1 Laboratory for Integrative Psychiatry, McLean Hospital, Belmont, USA.,2 Touro College of Osteopathic Medicine, New York, USA
| | | | - Hannah M Kramer
- 4 Multidisciplinary Association of Psychedelic Studies, Santa Cruz, USA
| | | | - John H Halpern
- 6 The Boston Center for Addiction Treatment, A Recovery Center of America Company, Danvers, USA.,7 Harvard Medical School, Laboratory for Integrative Psychiatry, Division of Alcohol and Drug Abuse, McLean Hospital, Belmont, USA
| | - Selma C Holden
- 8 University of New England, School of Osteopathic Medicine, Beth Israel Deaconess Medical Center, Boston, USA.,9 Beth Israel Deaconess Medical Center, Boston, USA
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Abstract
Classic hallucinogens share pharmacology as serotonin 5-HT2A, 5-HT2B, and 5-HT2C receptor agonists. Unique among most other Schedule 1 drugs, they are generally non-addictive and can be effective tools in the treatment of addiction. Mechanisms underlying these attributes are largely unknown. However, many preclinical studies show that 5-HT2C agonists counteract the addictive effects of drugs from several classes, suggesting this pharmacological property of classic hallucinogens may be significant. Drawing from a comprehensive analysis of preclinical behavior, neuroanatomy, and neurochemistry studies, this review builds rationale for this hypothesis, and also proposes a testable, neurobiological framework. 5-HT2C agonists work, in part, by modulating dopamine neuron activity in the ventral tegmental area-nucleus accumbens (NAc) reward pathway. We argue that activation of 5-HT2C receptors on NAc shell, GABAergic, medium spiny neurons inhibits potassium Kv1.x channels, thereby enhancing inhibitory activity via intrinsic mechanisms. Together with experiments that show that addictive drugs, such as cocaine, potentiate Kv1.x channels, thereby suppressing NAc shell GABAergic activity, this hypothesis provides a mechanism by which classic hallucinogen-mediated stimulation of 5-HT2C receptors could thwart addiction. It also provides a potential reason for the non-addictive nature of classic hallucinogens.
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Affiliation(s)
- Clinton E Canal
- Center for Drug Discovery, Department of Pharmaceutical Sciences, Northeastern University, Boston, USA
| | - Kevin S Murnane
- Department of Pharmaceutical Sciences, Mercer University College of Pharmacy, Mercer University Health Sciences Center, Atlanta, USA
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13
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Wyskiel DR, Andrade R. Serotonin excites hippocampal CA1 GABAergic interneurons at the stratum radiatum-stratum lacunosum moleculare border. Hippocampus 2016; 26:1107-14. [PMID: 27328460 PMCID: PMC4996712 DOI: 10.1002/hipo.22611] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/15/2016] [Indexed: 11/07/2022]
Abstract
The hippocampus receives robust serotonergic innervation that is thought to control the excitability of both pyramidal cells and GABAergic interneurons. Previous work has addressed serotonergic regulation of pyramidal cells but considerable gaps remain in our understanding of how serotonin regulates different interneuron subclasses. 5-HT2A receptors (5-HT2A Rs) appear to localize predominantly, if not solely, on interneurons in the hippocampus and have been implicated in the regulation of hippocampal function including mnemonic and novelty recognition processes. Interneurons are functionally diverse. Therefore in the current work, we have used a BAC transgenic mouse line expressing EGFP under the control of the 5-HT2A R promoter to identify the interneuron subtype(s) regulated by serotonin via 5-HT2A Rs. We find that EGFP expression in this mouse identifies a group of interneurons that resides predominantly along the border of the stratum radiatum (SR) and stratum lacunosum moleculare (SLM) of the CA1 region. We then show that these cells are depolarized and excited by serotonin acting through 5-HT2A Rs and appear to belong predominantly to the perforant pathway-associated and Schaffer collateral/commissural pathway-associated subtypes. These results indicate that serotonin interneurons expressing 5-HT2A Rs are localized primarily along the SR-SLM border of the CA1 region and represent a newly identified target for serotonin regulation in the hippocampus. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Daniel R Wyskiel
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, Michigan
| | - Rodrigo Andrade
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, Michigan
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Abstract
Psychedelics (serotonergic hallucinogens) are powerful psychoactive substances that alter perception and mood and affect numerous cognitive processes. They are generally considered physiologically safe and do not lead to dependence or addiction. Their origin predates written history, and they were employed by early cultures in many sociocultural and ritual contexts. After the virtually contemporaneous discovery of (5R,8R)-(+)-lysergic acid-N,N-diethylamide (LSD)-25 and the identification of serotonin in the brain, early research focused intensively on the possibility that LSD and other psychedelics had a serotonergic basis for their action. Today there is a consensus that psychedelics are agonists or partial agonists at brain serotonin 5-hydroxytryptamine 2A receptors, with particular importance on those expressed on apical dendrites of neocortical pyramidal cells in layer V. Several useful rodent models have been developed over the years to help unravel the neurochemical correlates of serotonin 5-hydroxytryptamine 2A receptor activation in the brain, and a variety of imaging techniques have been employed to identify key brain areas that are directly affected by psychedelics. Recent and exciting developments in the field have occurred in clinical research, where several double-blind placebo-controlled phase 2 studies of psilocybin-assisted psychotherapy in patients with cancer-related psychosocial distress have demonstrated unprecedented positive relief of anxiety and depression. Two small pilot studies of psilocybin-assisted psychotherapy also have shown positive benefit in treating both alcohol and nicotine addiction. Recently, blood oxygen level-dependent functional magnetic resonance imaging and magnetoencephalography have been employed for in vivo brain imaging in humans after administration of a psychedelic, and results indicate that intravenously administered psilocybin and LSD produce decreases in oscillatory power in areas of the brain's default mode network.
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Affiliation(s)
- David E Nichols
- Eschelman School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina
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15
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Buchborn T, Schröder H, Dieterich DC, Grecksch G, Höllt V. Tolerance to LSD and DOB induced shaking behaviour: differential adaptations of frontocortical 5-HT(2A) and glutamate receptor binding sites. Behav Brain Res 2015; 281:62-8. [PMID: 25513973 DOI: 10.1016/j.bbr.2014.12.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2014] [Revised: 12/04/2014] [Accepted: 12/06/2014] [Indexed: 12/20/2022]
Abstract
Serotonergic hallucinogens, such as lysergic acid diethylamide (LSD) and dimethoxy-bromoamphetamine (DOB), provoke stereotype-like shaking behaviour in rodents, which is hypothesised to engage frontocortical glutamate receptor activation secondary to serotonin2A (5-HT2A) related glutamate release. Challenging this hypothesis, we here investigate whether tolerance to LSD and DOB correlates with frontocortical adaptations of 5-HT2A and/or overall-glutamate binding sites. LSD and DOB (0.025 and 0.25 mg/kg, i.p.) induce a ketanserin-sensitive (0.5 mg/kg, i.p., 30-min pretreatment) increase in shaking behaviour (including head twitches and wet dog shakes), which with repeated application (7× in 4 ds) is undermined by tolerance. Tolerance to DOB, as indexed by DOB-sensitive [(3)H]spiroperidol and DOB induced [(35)S]GTP-gamma-S binding, is accompanied by a frontocortical decrease in 5-HT2A binding sites and 5-HT2 signalling, respectively; glutamate-sensitive [(3)H]glutamate binding sites, in contrast, remain unchanged. As to LSD, 5-HT2 signalling and 5-HT2A binding, respectively, are not or only marginally affected, yet [(3)H]glutamate binding is significantly decreased. Correlation analysis interrelates tolerance to DOB to the reduced 5-HT2A (r=.80) as well as the unchanged [(3)H]glutamate binding sites (r=.84); tolerance to LSD, as opposed, shares variance with the reduction in [(3)H]glutamate binding sites only (r=.86). Given that DOB and LSD both induce tolerance, one correlating with 5-HT2A, the other with glutamate receptor adaptations, it might be inferred that tolerance can arise at either level. That is, if a hallucinogen (like LSD in our study) fails to induce 5-HT2A (down-)regulation, glutamate receptors (activated postsynaptic to 5-HT2A related glutamate release) might instead adapt and thus prevent further overstimulation of the cortex.
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Affiliation(s)
- Tobias Buchborn
- Institute of Pharmacology and Toxicology, Otto-von-Guericke University, 39120 Magdeburg, Germany.
| | - Helmut Schröder
- Institute of Pharmacology and Toxicology, Otto-von-Guericke University, 39120 Magdeburg, Germany.
| | - Daniela C Dieterich
- Institute of Pharmacology and Toxicology, Otto-von-Guericke University, 39120 Magdeburg, Germany; Leibniz Institute for Neurobiology, Magdeburg, Germany; Center for Behavioral Brain Sciences (CBBS), Magdeburg, Germany.
| | - Gisela Grecksch
- Institute of Pharmacology and Toxicology, Otto-von-Guericke University, 39120 Magdeburg, Germany.
| | - Volker Höllt
- Institute of Pharmacology and Toxicology, Otto-von-Guericke University, 39120 Magdeburg, Germany.
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Halberstadt AL. Recent advances in the neuropsychopharmacology of serotonergic hallucinogens. Behav Brain Res 2015; 277:99-120. [PMID: 25036425 PMCID: PMC4642895 DOI: 10.1016/j.bbr.2014.07.016] [Citation(s) in RCA: 191] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Revised: 07/07/2014] [Accepted: 07/08/2014] [Indexed: 12/12/2022]
Abstract
Serotonergic hallucinogens, such as (+)-lysergic acid diethylamide, psilocybin, and mescaline, are somewhat enigmatic substances. Although these drugs are derived from multiple chemical families, they all produce remarkably similar effects in animals and humans, and they show cross-tolerance. This article reviews the evidence demonstrating the serotonin 5-HT2A receptor is the primary site of hallucinogen action. The 5-HT2A receptor is responsible for mediating the effects of hallucinogens in human subjects, as well as in animal behavioral paradigms such as drug discrimination, head twitch response, prepulse inhibition of startle, exploratory behavior, and interval timing. Many recent clinical trials have yielded important new findings regarding the psychopharmacology of these substances. Furthermore, the use of modern imaging and electrophysiological techniques is beginning to help unravel how hallucinogens work in the brain. Evidence is also emerging that hallucinogens may possess therapeutic efficacy.
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Affiliation(s)
- Adam L Halberstadt
- Department of Psychiatry, University of California San Diego, La Jolla, CA, United States.
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18
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Abstract
Only time will tell if serotonergic hallucinogen-assisted psychotherapy treatment paradigms for SUDs will prove to be safe and effective in double-blind, placebo-controlled clinical trials. If they are, they would truly constitute a novel psychopharmacologic-psychosocial treatment paradigm to treat addictive disorders, although the risk of adverse psychological events would have to be controlled through a careful screening process and the risk of misuse of the substances or developing use syndromes would have to be considered, although the overall risk would be low because, as mentioned, SHs are unlike all other drugs of abuse in that they do not appear to produce dependence syndromes. There effects on the NA and DA range from inhibition to slight activation, all this without producing addiction. The ability of these medicinal tools to treat a range of addictive, psychiatric, and existential disorders is remarkable in scope and possibility. They truly represent a potential paradigmatic shift within the field of psychiatry, too interesting to not explore further.
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Affiliation(s)
- Stephen Ross
- Division of Alcoholism and Drug Abuse, Bellevue Hospital Center and the New York University School of Medicine, New York, NY 10016, USA.
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Nijenhuis CM, Horst PGJT, Berg LTWDJVD, Wilffert B. Disturbed development of the enteric nervous system after in utero exposure of selective serotonin re-uptake inhibitors and tricyclic antidepressants. Part 1: Literature review. Br J Clin Pharmacol 2012; 73:16-26. [PMID: 21815911 DOI: 10.1111/j.1365-2125.2011.04075.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The increase in selective serotonin re-uptake inhibitor (SSRI) use during pregnancy, questions concerning abnormal development of the enteric nervous system (ENS), increase in laxative use in children and the association of fluoxetine with infantile hypertrophic pyloric stenosis (IHPS) gave rise to this pharmacological literature review. The role of 5-HT and the NE uptake in ontogeny of the ENS and the effects SSRIs and TCAs might have on the development of the ENS were investigated. The literature study showed that SSRIs may influence the development of the ENS in two ways. Blockage of the serotonin re-uptake transporter (SERT) during foetal development could influence migration, differentiation and survival of cells. This could lead to abnormal development in the first trimester of pregnancy. The other way is that 5-HT seems to be a growth factor in the primitive ENS. This growth factor like action is mediated through the 5-HT(2B) receptor and stimulation of this receptor by SSRIs influences the fate of late-developing enteric neurons. This could lead to abnormal development in the second and third trimester. TCAs could influence the development of the ENS, besides through inhibition of the SERT, through inhibition of the norepinephrine transporter (NET). Expression of the NET seems to be essential for a full development of enteric neurons and especially for serotonergic neurons. In addition the NET was detected early in ontogeny and precedes neuronal differentiation, which suggests that TCAs might influence development of the ENS when exposed early in pregnancy. The insights of this study gave rise to hypotheses which will be tested in an epidemiological cohort study.
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Affiliation(s)
- Cynthia M Nijenhuis
- Department of Pharmaco-epidemiology and Pharmaco-economy, University of Groningen, Groningen, The Netherlands
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21
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Halberstadt AL, Geyer MA. Multiple receptors contribute to the behavioral effects of indoleamine hallucinogens. Neuropharmacology 2011; 61:364-81. [PMID: 21256140 PMCID: PMC3110631 DOI: 10.1016/j.neuropharm.2011.01.017] [Citation(s) in RCA: 236] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2010] [Revised: 12/03/2010] [Accepted: 01/10/2011] [Indexed: 10/18/2022]
Abstract
Serotonergic hallucinogens produce profound changes in perception, mood, and cognition. These drugs include phenylalkylamines such as mescaline and 2,5-dimethoxy-4-methylamphetamine (DOM), and indoleamines such as (+)-lysergic acid diethylamide (LSD) and psilocybin. Despite their differences in chemical structure, the two classes of hallucinogens produce remarkably similar subjective effects in humans, and induce cross-tolerance. The phenylalkylamine hallucinogens are selective 5-HT(2) receptor agonists, whereas the indoleamines are relatively non-selective for serotonin (5-HT) receptors. There is extensive evidence, from both animal and human studies, that the characteristic effects of hallucinogens are mediated by interactions with the 5-HT(2A) receptor. Nevertheless, there is also evidence that interactions with other receptor sites contribute to the psychopharmacological and behavioral effects of the indoleamine hallucinogens. This article reviews the evidence demonstrating that the effects of indoleamine hallucinogens in a variety of animal behavioral paradigms are mediated by both 5-HT(2) and non-5-HT(2) receptors.
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Affiliation(s)
- Adam L Halberstadt
- Department of Psychiatry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, United States.
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22
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Dougherty JP, Aloyo VJ. Pharmacological and behavioral characterization of the 5-HT2A receptor in C57BL/6N mice. Psychopharmacology (Berl) 2011; 215:581-93. [PMID: 21340474 DOI: 10.1007/s00213-011-2207-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Accepted: 01/27/2011] [Indexed: 11/30/2022]
Abstract
RATIONALE The serotonin (5-HT) 2A receptor is implicated in numerous psychiatric disorders, making it an important, clinically relevant target. Despite the availability of transgenic mouse lines, the native mouse 5-HT(2A) receptor is not well-characterized. OBJECTIVES The goals of the current study were to determine 5-HT(2A) and 5-HT(2C) receptor densities in mouse cortex, establish a pharmacological profile of the mouse 5-HT(2A) receptor, and determine the effects of chronic drug treatment on 5-HT(2A) receptor density and 5-HT(2A) receptor-mediated behavior. METHODS Receptor densities were determined in cortex and frontal cortex via saturation binding assays using [(3)H]ketanserin or [(3)H]mesulergine. A pharmacological profile was established by displacing [(3)H]ketanserin binding with several ligands. Chronic treatment with 5-HT(2A/2C) receptor agonist, 2,5-dimethoxy-4-iodoamphetamine (DOI), 5-HT(2A) receptor antagonist, MDL 11939, or vehicle was followed by 5-HT(2A) receptor density determination. Head twitch responses (HTRs) were counted on select days. RESULTS Mice had high 5-HT(2A), but low 5-HT(2C) receptor densities. Ligand binding affinities for mouse 5-HT(2A) receptors correlated with rat, but not rabbit or human, affinities. Chronically DOI-treated mice displayed reduced HTRs and 5-HT(2A) receptor density compared to saline-treated mice. Receptor density was unchanged following chronic treatment with MDL 11939. CONCLUSIONS The current study provides some basic information about mouse 5-HT(2A) and 5-HT(2C) receptors and provides comparisons to rats, rabbits, and humans. The current chronic agonist treatment study demonstrated an important similarity between the 5-HT(2A) receptor in mice, rats, and rabbits, while antagonist treatment revealed an interesting difference from previous studies in rabbits.
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Affiliation(s)
- John P Dougherty
- Drexel University College of Medicine, Philadelphia, PA 19102, USA.
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Nic Dhonnchadha B, Fox R, Stutz S, Rice KC, Cunningham K. Blockade of the serotonin 5-HT2A receptor suppresses cue-evoked reinstatement of cocaine-seeking behavior in a rat self-administration model. Behav Neurosci 2009; 123:382-96. [PMID: 19331461 PMCID: PMC3830454 DOI: 10.1037/a0014592] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The serotonin 5-HT2A receptor (5-HT-sub(2A)R) may play a role in reinstatement of drug-seeking. This study investigated the ability of a selective 5-HT-sub(2A)R antagonist to suppress reinstatement evoked by exposure to cues conditioned to cocaine self-administration. Cocaine self-administration (0.75 mg/kg/0.1 mL/6 s infusion; FR 4) was trained in naïve, free-fed rats to allow interpretation of results independent from changes related to food deprivation stress. Pretreatment with the selective 5-HT-sub(2A)R antagonist M100907 (volinanserin) failed to reduce rates of operant responding for cocaine infusions. On the other hand, M100907 (0.001-0.8 mg/kg ip) significantly suppressed the cue-induced reinstatement of cocaine-seeking behavior following extinction; effective M100907 doses did not alter operant responding for cues previously associated with sucrose self-administration. Importantly, a greater magnitude of active lever presses on the initial extinction session (high extinction responders) predicted the maximal susceptibility to M100907-induced suppression of cue-evoked reinstatement. The findings indicate that blockade of the 5-HT-sub(2A)R attenuates the incentive-motivational effects of cocaine-paired cues, particularly in high extinction responders, and suggests that M100907 may afford a therapeutic advance in suppression of cue-evoked craving and/or relapse.
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Affiliation(s)
- B.Á. Nic Dhonnchadha
- Center for Addiction Research, Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - R.G. Fox
- Center for Addiction Research, Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - S.J. Stutz
- Center for Addiction Research, Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - K. C. Rice
- Chemical Biology Research Branch, Drug Design and Synthesis Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Bethesda, MD 20892, USA
| | - K.A. Cunningham
- Center for Addiction Research, Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX 77555, USA
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Reissig CJ, Eckler JR, Rabin RA, Rice KC, Winter JC. The stimulus effects of 8-OH-DPAT: evidence for a 5-HT2A receptor-mediated component. Pharmacol Biochem Behav 2007; 88:312-7. [PMID: 17936346 DOI: 10.1016/j.pbb.2007.09.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2007] [Revised: 08/29/2007] [Accepted: 09/06/2007] [Indexed: 10/22/2022]
Abstract
A previous investigation in our laboratory found that the stimulus effects of the 5-HT2A agonist, LSD, are potentiated by 5-HT1A receptor agonists including the prototypic agonist, 8-OH-DPAT. Also suggestive of behaviorally relevant interactions between 5-HT1A and 5-HT2A receptors are behavioral analyses of locomotor activity, head-twitch response, forepaw treading and production of the serotonin syndrome; in some instances effects are augmented, in other, diminished. These observations led us in the present investigation to test the hypothesis that stimulus control by 8-OH-DPAT [0.2 mg/kg; 15 min pretreatment time] is modulated by 5-HT2A ligands. Stimulus control was established with 8-OH-DPAT in a group of 10 rats. A two-lever, fixed ratio 10, positively reinforced task with saline controls was employed. As shown previously, stimulus control by 8-OH-DPAT and the generalization of 8-OH-DPAT to the 5-HT1A partial agonist, buspirone, was completely blocked by the selective 5-HT1A antagonist, WAY-100635. In contrast, antagonism by the selective 5-HT2A antagonist, M100907 [0.1 mg/kg; 30 min pretreatment time], of 8-OH-DPAT and of the generalization of 8-OH-DPAT to buspirone was statistically significant but less than complete. In light of our previous conclusions regarding the interactions of 5-HT1A agonists with LSD-induced stimulus control, the present data suggest that the interaction between 5-HT1A and 5-HT2A receptors is bidirectional in drug discrimination studies.
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Affiliation(s)
- C J Reissig
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14214-3000, USA
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Fantegrossi WE, Murnane KS, Reissig CJ. The behavioral pharmacology of hallucinogens. Biochem Pharmacol 2007; 75:17-33. [PMID: 17977517 DOI: 10.1016/j.bcp.2007.07.018] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2007] [Revised: 07/11/2007] [Accepted: 07/13/2007] [Indexed: 11/25/2022]
Abstract
Until very recently, comparatively few scientists were studying hallucinogenic drugs. Nevertheless, selective antagonists are available for relevant serotonergic receptors, the majority of which have now been cloned, allowing for reasonably thorough pharmacological investigation. Animal models sensitive to the behavioral effects of the hallucinogens have been established and exploited. Sophisticated genetic techniques have enabled the development of mutant mice, which have proven useful in the study of hallucinogens. The capacity to study post-receptor signaling events has lead to the proposal of a plausible mechanism of action for these compounds. The tools currently available to study the hallucinogens are thus more plentiful and scientifically advanced than were those accessible to earlier researchers studying the opioids, benzodiazepines, cholinergics, or other centrally active compounds. The behavioral pharmacology of phenethylamine, tryptamine, and ergoline hallucinogens are described in this review, paying particular attention to important structure activity relationships which have emerged, receptors involved in their various actions, effects on conditioned and unconditioned behaviors, and in some cases, human psychopharmacology. As clinical interest in the therapeutic potential of these compounds is once again beginning to emerge, it is important to recognize the wealth of data derived from controlled preclinical studies on these compounds.
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Affiliation(s)
- William E Fantegrossi
- Division of Neuroscience, Yerkes National Primate Research Center, Emory University, 954 Gatewood Road NE, Atlanta, GA 30322, USA.
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Dave KD, Harvey JA, Aloyo VJ. The Time-Course for Up- and Down-Regulation of the Cortical 5-Hydroxytryptamine (5-HT)2A Receptor Density Predicts 5-HT2A Receptor-Mediated Behavior in the Rabbit. J Pharmacol Exp Ther 2007; 323:327-35. [PMID: 17640952 DOI: 10.1124/jpet.107.121707] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
5-Hydroxytryptamine (serotonin; 5-HT)2 receptor agonists such as (+/-)-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) injected systemically or directly into frontal cortex, elicit stereotyped head movements that are mediated by 5-HT2A receptors. Chronic administration of 5-HT2A receptor antagonists can produce either a down-regulation, e.g., d-2-bromolysergic acid diethylamide (BOL) or an up-regulation, e.g., alpha-phenyl-10(2-phenylethyl)-4-piperidinemethanol (MDL11,939) of cortical 5-HT2A receptors in the rabbit with no change in the density of the 5-HT2C receptor. We examined the degree to which the time course for the onset and offset of changes in cortical 5-HT2A receptor density was correlated with functional changes as measured by the magnitude of DOI elicited, 5-HT2A receptor-mediated head movements (head bobs). First, the magnitude of DOI-elicited head bobs was measured over 1 to 8 days after chronic BOL (5.8 micromol/kg), MDL11,939 (10 micromol/kg), or vehicle administration. Second, rabbits were injected with BOL, MDL11,939, or vehicle once daily for 8 days, and then, 1 to 8 days after the cessation of drug or vehicle, DOI-elicited head bobs were determined. Samples of frontal cortex were obtained for each animal immediately following behavioral testing, and 5-HT2A receptor density was measured using [3H]ketanserin. Thus, each animal provided a value for receptor density and number of head bobs, and these two measures showed a high degree of correlation between 0.94 for BOL and 0.95 for MDL11,939. This study establishes that the density of 5-HT2A receptors in cortex reflects their functional status.
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Affiliation(s)
- Kuldip D Dave
- Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 N. 15th Street, 8th Floor, NCB, Mail stop 488, Philadelphia, PA 19102, USA.
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Hanff LM, Gupta S, MaassenVanDenBrink A, Steegers EAP, Saxena PR, Vulto AG, Visser W. The effect of maternal ketanserin treatment on foetal 5-HT receptor function in umbilical cord artery of pre-eclamptic patients. Neonatology 2007; 92:240-7. [PMID: 17556842 DOI: 10.1159/000103742] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2006] [Accepted: 01/29/2007] [Indexed: 11/19/2022]
Abstract
BACKGROUND Maternal treatment with the 5-HT(2A) receptor antagonist ketanserin (KT) in pre-eclamptic patients is associated with a high placental transmission of KT, resulting in pharmacologically active levels of KT in the umbilical cord artery (UCA) and the neonate. Prolonged exposure to a 5-HT receptor antagonist may influence the functionality of foetal 5-HT receptors and compromise foetal development. OBJECTIVE To study whether exposure to KT influences the characteristics of foetal 5-HT receptors, functional studies were performed on 5-HT(2A) and 5-HT(1B/1D) receptors in UCA from pre-eclamptic patients treated with KT. METHODS UCAs were obtained, immediately after delivery, from pre-eclamptic patients (n = 7), treated antenatally with intravenous KT. Pre-eclamptic patients (n = 13), not treated with KT (non-KT), were included as a control group. Segments of UCA were prepared and mounted in tissue baths and isometric force changes were determined. Cumulative concentration response curves to 5-HT and to the 5-HT(1B/1D )receptor agonist sumatriptan were constructed in the absence or presence of the 5-HT(2A) receptor antagonist KT or the 5-HT(1B/1D) receptor antagonist GR125743, respectively. RESULTS All UCA segments showed contractile responses to both 5-HT and sumatriptan, and the concentration response curves showed a rightward shift with increasing concentrations of KT and GR125743, respectively, indicating the presence of functional 5-HT(2A) and 5-HT(1B/1D) receptors in the foetal tissue. No significant differences were found in maximum response (E(max))(expressed in percent of response on 100 mM KCl) or potency (pEC(50)) of 5-HT in both groups (E(max) = 141 +/- 7.7%, pEC(50) = 7.67 +/- 0.26 in KT-treated group and E(max) = 162 +/- 12.6%, pEC(50) = 7.69 +/- 0.14 in non-KT treated group, respectively). No significant differences were found in the potency of the antagonist KT in both study groups (pK(b) = 7.65 +/- 0.31 in KT group and 7.46 +/- 0.17 in non-KT group, respectively). Similarly, with sumatriptan, no significant differences were found between KT-treated patients and non-KT treated patients (E(max) = 142 +/- 16.2 and 140 +/- 14.7%, respectively, pEC(50) = 6.17 +/- 0.37 and 6.41 +/- 0.28 respectively, pK(b) of GR125743 = 7.83 +/- 0.48 and 8.43 +/- 0.29, respectively). CONCLUSION Foetal exposure to KT in pre-eclamptic patients does not seem to influence the functional characteristics of 5-HT(2A) and 5-HT(1B/1D) receptors in the UCA.
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Affiliation(s)
- L M Hanff
- Department of Hospital Pharmacy, Erasmus University Medical Centre, Rotterdam, The Netherlands.
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Hayslett RL, Tizabi Y. Effects of donepezil, nicotine and haloperidol on the central serotonergic system in mice: implications for Tourette's syndrome. Pharmacol Biochem Behav 2005; 81:879-86. [PMID: 16045972 DOI: 10.1016/j.pbb.2005.06.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2005] [Revised: 06/08/2005] [Accepted: 06/14/2005] [Indexed: 02/04/2023]
Abstract
We have previously reported that acute and chronic donepezil and nicotine administration significantly attenuate DOI-induced head twitch response (HTR) in mice. This behavior, primarily mediated by stimulation of 5-HT2A receptors, has been proposed to model tic symptoms seen in Tourette's syndrome (TS). Haloperidol, a drug widely used to treat symptoms of TS, has also been reported to reduce DOI-induced head shakes in rodents when administered acutely. These findings suggest an inhibitory interaction of these drugs with 5-HT2A receptors. To test this hypothesis, we evaluated the effects of chronic donepezil, nicotine and haloperidol on expression levels of 5-HT2A mRNA and 5-HT2A receptor density in select brain regions. Initially, we established a dose-response relationship for the acute and chronic haloperidol and DOI-induced HTR. Male ICR mice were treated twice daily with donepezil (0.1 mg/kg), nicotine (0.5 mg/kg), and once daily with haloperidol (0.4 mg/kg) for 14 days and were sacrificed 16-18 h after the last injection. These drug regimens were chosen because of their significant effects on DOI-induced HTR. Donepezil significantly increased 5-HT2A mRNA level, but not the receptor density in the striatum. In the midbrain, donepezil significantly decreased the receptor density without affecting the 5-HT2A mRNA level. In the frontal cortex, only haloperidol significantly reduced the 5-HT2A receptor density. The cortex was the only area where donepezil, nicotine and haloperidol significantly reduced the 5-HT2A receptor density. The results suggest that the anti-tic properties of donepezil, nicotine and haloperidol in this paradigm might be due to antagonism of cortical 5-HT2A receptors. Thus, further investigation of involvement of cortical 5-HT2A receptors in TS as well as evaluation of selective 5-HT2A receptor antagonists in this disorder is warranted.
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MESH Headings
- Amphetamines/pharmacology
- Animals
- Behavior, Animal/drug effects
- Binding, Competitive/drug effects
- Cerebral Cortex/drug effects
- Cerebral Cortex/metabolism
- Corpus Striatum/drug effects
- Corpus Striatum/metabolism
- Donepezil
- Dose-Response Relationship, Drug
- Frontal Lobe/drug effects
- Frontal Lobe/metabolism
- Gene Expression/drug effects
- Haloperidol/pharmacology
- Humans
- Indans/pharmacology
- Ketanserin/pharmacology
- Male
- Mesencephalon/drug effects
- Mesencephalon/metabolism
- Mice
- Mice, Inbred ICR
- Nicotine/pharmacology
- Piperidines/pharmacology
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptor, Serotonin, 5-HT2A/genetics
- Receptor, Serotonin, 5-HT2A/metabolism
- Receptors, Serotonin/genetics
- Receptors, Serotonin/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Serotonin Antagonists/pharmacology
- Tourette Syndrome/drug therapy
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Affiliation(s)
- Renee L Hayslett
- Department of Pharmacology, Howard University College of Medicine, 520 W Street N.W., Washington, DC 20059, USA
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29
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Gresch PJ, Smith RL, Barrett RJ, Sanders-Bush E. Behavioral tolerance to lysergic acid diethylamide is associated with reduced serotonin-2A receptor signaling in rat cortex. Neuropsychopharmacology 2005; 30:1693-702. [PMID: 15756304 DOI: 10.1038/sj.npp.1300711] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Tolerance is defined as a decrease in responsiveness to a drug after repeated administration. Tolerance to the behavioral effects of hallucinogens occurs in humans and animals. In this study, we used drug discrimination to establish a behavioral model of lysergic acid diethylamide (LSD) tolerance and examined whether tolerance to the stimulus properties of LSD is related to altered serotonin receptor signaling. Rats were trained to discriminate 60 microg/kg LSD from saline in a two-lever drug discrimination paradigm. Two groups of animals were assigned to either chronic saline treatment or chronic LSD treatment. For chronic treatment, rats from each group were injected once per day with either 130 microg/kg LSD or saline for 5 days. Rats were tested for their ability to discriminate either saline or 60 microg/kg LSD, 24 h after the last chronic injection. Rats receiving chronic LSD showed a 44% reduction in LSD lever selection, while rats receiving chronic vehicle showed no change in percent choice on the LSD lever. In another group of rats receiving the identical chronic LSD treatment, LSD-stimulated [35S]GTPgammaS binding, an index of G-protein coupling, was measured in the rat brain by autoradiography. After chronic LSD, a significant reduction in LSD-stimulated [35S]GTPgammaS binding was observed in the medial prefrontal cortex and anterior cingulate cortex. Furthermore, chronic LSD produced a significant reduction in 2,5-dimethoxy-4-iodoamphetamine-stimulated [35S]GTPgammaS binding in medial prefrontal cortex and anterior cingulate cortex, which was blocked by MDL 100907, a selective 5-HT2A receptor antagonist, but not SB206553, a 5-HT2C receptor antagonist, indicating a reduction in 5-HT2A receptor signaling. 125I-LSD binding to 5-HT2A receptors was reduced in cortical regions, demonstrating a reduction in 5-HT2A receptor density. Taken together, these results indicate that adaptive changes in LSD-stimulated serotonin receptor signaling may mediate tolerance to the discriminative stimulus effects of LSD.
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Affiliation(s)
- Paul J Gresch
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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30
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Doat-Meyerhoefer MM, Hard R, Winter JC, Rabin RA. Effects of clozapine and 2,5-dimethoxy-4-methylamphetamine [DOM] on 5-HT2A receptor expression in discrete brain areas. Pharmacol Biochem Behav 2005; 81:750-7. [PMID: 15972234 PMCID: PMC1351091 DOI: 10.1016/j.pbb.2005.05.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2005] [Revised: 05/10/2005] [Accepted: 05/23/2005] [Indexed: 11/19/2022]
Abstract
Activation of 5-HT2A receptors has been shown to be an essential component of the discriminative stimulus effects of indoleamine and phenethylamine hallucinogens. The objective of the present study was to determine the neuroanatomical location of the 5HT2A receptors which may be responsible for the stimulus effects of the phenethylamine hallucinogen [-]2,5-dimethoxy-4-methylamphetamine (DOM). It was hypothesized that brain areas containing altered 5-HT2A receptor expression in the context of a similar alteration in DOM-induced stimulus control might be important in mediating the stimulus effects of DOM. Fisher 344 rats were treated with either clozapine (25 mg/kg/day) or DOM (2 mg/kg/day) for 7 days, and the consequences of these drug treatment regimens on DOM-induced stimulus control and on 5-HT2A receptor expression in several brain areas were determined. Chronic administration of clozapine was associated with a wide-spread decrease in levels of 5-HT2A/2C receptors. Conversely, treatment with DOM had varied effects including a neuroanatomically selective decrease in 5-HT2A/2C receptor levels that was restricted to the olfactory nucleus. Both chronic treatment with DOM and clozapine decreased the stimulus effects of DOM. The present findings suggest a role for the olfactory nucleus in producing the stimulus effects of DOM.
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Affiliation(s)
| | - R Hard
- Department of Pathology and Anatomical Sciences, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY 14214
| | - JC Winter
- Department of Pharmacology and Toxicology, and
| | - RA Rabin
- Department of Pharmacology and Toxicology, and
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31
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Abstract
Hallucinogens (psychedelics) are psychoactive substances that powerfully alter perception, mood, and a host of cognitive processes. They are considered physiologically safe and do not produce dependence or addiction. Their origin predates written history, and they were employed by early cultures in a variety of sociocultural and ritual contexts. In the 1950s, after the virtually contemporaneous discovery of both serotonin (5-HT) and lysergic acid diethylamide (LSD-25), early brain research focused intensely on the possibility that LSD or other hallucinogens had a serotonergic basis of action and reinforced the idea that 5-HT was an important neurotransmitter in brain. These ideas were eventually proven, and today it is believed that hallucinogens stimulate 5-HT(2A) receptors, especially those expressed on neocortical pyramidal cells. Activation of 5-HT(2A) receptors also leads to increased cortical glutamate levels presumably by a presynaptic receptor-mediated release from thalamic afferents. These findings have led to comparisons of the effects of classical hallucinogens with certain aspects of acute psychosis and to a focus on thalamocortical interactions as key to understanding both the action of these substances and the neuroanatomical sites involved in altered states of consciousness (ASC). In vivo brain imaging in humans using [(18)F]fluorodeoxyglucose has shown that hallucinogens increase prefrontal cortical metabolism, and correlations have been developed between activity in specific brain areas and psychological elements of the ASC produced by hallucinogens. The 5-HT(2A) receptor clearly plays an essential role in cognitive processing, including working memory, and ligands for this receptor may be extremely useful tools for future cognitive neuroscience research. In addition, it appears entirely possible that utility may still emerge for the use of hallucinogens in treating alcoholism, substance abuse, and certain psychiatric disorders.
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Affiliation(s)
- David E Nichols
- Department of Medicinal Chemistry and Molecular Pharmacology, School of Pharmacy and Pharmacal Sciences, Purdue University, West Lafayette, IN 47907-2091, USA.
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32
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Regina MJ, Winter JC, Rabin RA. Characterization of a novel effect of serotonin 5-HT1A and 5-HT2A receptors: increasing cGMP levels in rat frontal cortex. Neuropharmacology 2004; 45:1041-9. [PMID: 14614947 DOI: 10.1016/s0028-3908(03)00287-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Elucidating the mechanisms of action of hallucinogens has become an increasingly important area of research as their abuse has grown in recent years. Although serotonin receptors appear to play a role in the behavioral effects of the phenethylamine and indoleamine hallucinogens, the signaling pathways activated by these agents are unclear. Here it is shown that administration of serotonin (5-hydroxytryptamine, 5-HT) increased cyclic guanosine monophosphate (cGMP) production in frontal cortical slices of rat brain. The effect of 5-HT was greater than that of N-methyl-D-aspartate (NMDA), a stimulant of cGMP formation in the central nervous system. The 5-HT(2A/2C) receptor phenethylamine agonist, 2,5-dimethoxy-4-methylamphetamine (DOM), increased cGMP content in the slices. Additionally 8-hydroxy-2-(di-n-propylamino)tetralin (DPAT), a 5-(HT1A/7) receptor agonist also increased cGMP production. Stimulation of cGMP formation by DOM was prevented by a 5-HT(2A/2C) receptor antagonist, pirenperone, as well as by a 5-HT2A receptor selective antagonist, MDL100907. A 5-HT2C receptor antagonist, SB242084, did not block the effect of DOM. Stimulation of cGMP production by DPAT was blocked by the 5-HT1A receptor antagonist, WAY100635. Stimulation of cGMP formation by serotonin could be prevented by pirenperone or WAY100635. In summary, activation of serotonin 5-HT1A and 5-HT2A receptors increase brain cGMP levels.
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Affiliation(s)
- Meredith J Regina
- SUNY-Buffalo, Department of Pharmacology and Toxicology, 102 Farber Hall, Buffalo, NY 14214-3000, USA
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33
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Enguix MJ, Sánchez L, Villazón M, Brea J, Tristán H, Caruncho HJ, Cadavid MI, Loza MI. Differential regulation of rat peripheral 5-HT(2A) and 5-HT(2B) receptor systems: influence of drug treatment. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2003; 368:79-90. [PMID: 12861437 DOI: 10.1007/s00210-003-0775-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2002] [Accepted: 05/08/2003] [Indexed: 10/26/2022]
Abstract
Most studies of 5-HT(2) receptor regulation have been carried out on the central nervous system (CNS) (which expresses 5-HT(2A) and 5-HT(2C) receptors); very few in vitro studies have addressed the peripheral receptors 5-HT(2A) and 5-HT(2B). The aim of this investigation was to compare the possible short- and long-term processes regulating these peripheral receptors in the rat. The in vitro contractile response elicited by serotonin (5-HT, 10 micro M) in the rat gastric fundus (5-HT(2B) receptor system) was rapid and followed by a partial fade to a steady state, in contrast with the rat thoracic aorta response (5-HT(2A) receptor system), which was more stable, slower and sustained. To characterize drug-receptor interactions, cumulative concentration/response curves (CCRCs) for 5-HT were constructed ex vivo for rat tissues treated with drugs acting at these receptors. Rats were examined 4 or 24 h after a single, i.p. administration of (+/-)1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane [(+/-)DOI, 1 or 2.5 mg/kg], clozapine, cyproheptadine or rauwolscine (10 mg/kg), 48 h after a single i.p. administration of (+/-)DOI (2.5 mg/kg), clozapine or cyproheptadine (10 mg/kg) or 24 h after the last of with 15 daily i.p. administrations of (+/-)DOI (1 or 2.5 mg/kg), clozapine, cyproheptadine or rauwolscine (10 mg/kg). In the aorta, E(max) (the maximum response elicited by 5-HT) was unchanged 4 h after a single dose of any of the drugs tested. However, 24 h after a single dose, E(max) was lower in animals treated with (+/-)DOI (2.5 mg/kg), clozapine or cyproheptadine than in controls, whilst 48 h after a single dose of (+/-)DOI (2.5 mg/kg), clozapine or cyproheptadine there was no difference in E(max) between experimental and control animals. After chronic treatment with (+/-)DOI (2.5 mg/kg), clozapine and cyproheptadine, E(max) was lower than in controls. In the gastric fundus, E(max) 4 h after a single dose of each drug was lower than in controls, and the response recovered by 24 or 48 h. Following chronic treatment, E(max) was significantly lower than in controls for each drug used. These findings suggest first, that regulation of peripheral 5-HT(2) receptors (5-HT(2A) and 5-HT(2B)) is a functionally significant phenomenon in vivo, and occurs after administration of both agonists and antagonists. Second, the kinetics of peripheral 5-HT(2) receptor regulation were similar in both in vivo and ex vivo experiments. The 5-HT(2B) receptors in rat gastric fundus are more sensitive to drug-induced regulation than the 5-HT(2A) rat aortic receptors. Finally, long-term regulation of both receptors stabilizes short-term desensitization for longer.
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MESH Headings
- Amphetamines/pharmacology
- Animals
- Antipsychotic Agents/pharmacology
- Aorta, Thoracic/drug effects
- Aorta, Thoracic/metabolism
- Aorta, Thoracic/physiology
- Clozapine/pharmacology
- Cyproheptadine/pharmacology
- Gastric Fundus/drug effects
- Gastric Fundus/metabolism
- Gastric Fundus/physiology
- In Vitro Techniques
- Ligands
- Male
- Muscle Contraction/drug effects
- Muscle, Smooth/drug effects
- Muscle, Smooth/metabolism
- Muscle, Smooth/physiology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/physiology
- Rats
- Rats, Sprague-Dawley
- Receptor, Serotonin, 5-HT2A/drug effects
- Receptor, Serotonin, 5-HT2A/metabolism
- Receptor, Serotonin, 5-HT2B/drug effects
- Receptor, Serotonin, 5-HT2B/metabolism
- Serotonin/metabolism
- Serotonin Antagonists/pharmacology
- Serotonin Receptor Agonists/pharmacology
- Yohimbine/pharmacology
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Affiliation(s)
- M J Enguix
- School of Pharmacy, University of Santiago de Compostela, 15782, Santiago de Compostela, Spain
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34
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Eckler JR, Chang-Fong J, Rabin RA, Smith C, Teitler M, Glennon RA, Winter JC. Behavioral characterization of 2-O-desmethyl and 5-O-desmethyl metabolites of the phenylethylamine hallucinogen DOM. Pharmacol Biochem Behav 2003; 75:845-52. [PMID: 12957227 DOI: 10.1016/s0091-3057(03)00159-x] [Citation(s) in RCA: 7] [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: 11/29/2022]
Abstract
The present investigation was undertaken to test the hypothesis that known metabolites of the phenylethylamine hallucinogen 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM) are pharmacologically active. This hypothesis was tested by evaluating the ability of racemic DOM metabolites 2-O-desmethyl DOM (2-DM-DOM) and 5-O-desmethyl DOM (5-DM-DOM) to substitute for the stimulus properties of (+)lysergic acid diethylamide (LSD). The data indicate that both metabolites are active in LSD-trained subjects and are significantly inhibited by the selective 5-HT(2A) receptor antagonist M100907. Full generalization of LSD to both 2-DM-DOM and 5-DM-DOM occurred, and 5-DM-DOM was slightly more potent than 2-DM-DOM. Similarly, 5-DM-DOM had a slightly higher affinity than 2-DM-DOM for both 5-HT(2A) and 5-HT(2C) receptors. Additionally, it was of interest to determine if the formation of active metabolite(s) resulted in a temporal delay associated with maximal stimulus effects of DOM. We postulated that if metabolite formation resulted in the aforementioned delay, direct administration of the metabolites might result in maximally stable stimulus effects at an earlier pretreatment time. This hypothesis was tested by evaluating (1) the time point at which DOM produces the greatest degree of LSD-appropriate responding, (2) the involvement of 5-HT(2A) receptor in the stimulus effects of DOM at various pretreatment times by administration of M100907 and (3) the ability of 2-DM-DOM and 5-DM-DOM to substitute for the stimulus properties of LSD using either 15- or 75-min pretreatment time. The data indicate that (a) the DOM stimulus produces the greatest degree of LSD-appropriate responding at the 75-min time point in comparison with earlier pretreatment times and (b) the stimulus effects of DOM are differentially antagonized by M100907 and this effect is a function of DOM pretreatment time prior to testing. Both 2-DM-DOM and 5-DM-DOM were found to be most active, at all doses tested, using a 75-min versus a 15-min pretreatment time. The present data do not permit unequivocal acceptance or rejection of the hypothesis that active metabolites of (-)-DOM provide a full explanation of the observed discrepancy between brain levels of (-)-DOM and maximal stimulus effects.
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Affiliation(s)
- J R Eckler
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, 14214-3000, USA.
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35
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Eckler JR, Rabin RA, Winter JC. Nefazodone in the rat: mimicry and antagonism of [-]-DOM-induced stimulus control. Pharmacol Biochem Behav 2003; 75:405-10. [PMID: 12873632 DOI: 10.1016/s0091-3057(03)00132-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Nefazodone is presently marketed as an antidepressant that inhibits both serotonin (5-hydroxytryptamine, 5-HT) and norepinephrine reuptake while antagonizing pirenpirone (5-HT2) receptors. This 5-HT receptor type is believed to play a prominent role in the underlying mechanism of action of serotonergic hallucinogens. Antidepressant medications now represent the most commonly prescribed psychoactive medications in the world and are likely to be ingested in the presence of hallucinogens with increased frequency; the consequences are largely unknown. The present investigation examined the interaction between the serotonergic phenethylamine hallucinogen [-]-2,5-dimethoxy-4-methylamphetamine ([-]-DOM), and nefazodone, in rats trained with [-]-DOM [0.6 mg/kg; 75 min pretreatment time] as a discriminative stimulus. The data indicate that maximal substitution of nefazodone for the [-]-DOM stimulus was present using a 45-min pretreatment time before testing. Using this pretreatment time, a dose of nefazodone of 12.0 mg/kg administered alone resulted in 76% DOM-appropriate responding. When a range of doses of nefazodone was combined with the training dose of [-]-DOM, a pattern of responding compatible with partial agonism was observed. The intermediate degree of [-]-DOM generalization to nefazodone was significantly antagonized by the 5-HT antagonists, 5-HT2, SR 46349B (5HT2A/2C), and M100907 (5-HT2A). Taken together, the present data suggest that (a) nefazodone acts as a partial agonist and (b) these effects are mediated by the 5-HT2A receptor.
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Affiliation(s)
- J R Eckler
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, 102 Farber Hall, Buffalo, NY 14214-3000, USA.
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36
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Van Oekelen D, Luyten WHML, Leysen JE. 5-HT2A and 5-HT2C receptors and their atypical regulation properties. Life Sci 2003; 72:2429-49. [PMID: 12650852 DOI: 10.1016/s0024-3205(03)00141-3] [Citation(s) in RCA: 148] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The 5-HT(2A) and 5-HT(2C) receptors belong to the G-protein-coupled receptor (GPCR) superfamily. GPCRs transduce extracellular signals to the interior of cells through their interaction with G-proteins. The 5-HT(2A) and 5-HT(2C) receptors mediate effects of a large variety of compounds affecting depression, schizophrenia, anxiety, hallucinations, dysthymia, sleep patterns, feeding behaviour and neuro-endocrine functions. Binding of such compounds to either 5-HT(2) receptor subtype induces processes that regulate receptor sensitivity. In contrast to most other receptors, chronic blockade of 5-HT(2A) and 5-HT(2C) receptors leads not to an up- but to a (paradoxical) down-regulation. This review deals with published data involving such non-classical regulation of 5-HT(2A) and 5-HT(2C) receptors obtained from in vivo and in vitro studies. The underlying regulatory processes of the agonist-induced regulation of 5-HT(2A) and 5-HT(2C) receptors, commonly thought to be desensitisation and resensitisation, are discussed. The atypical down-regulation of both 5-HT(2) receptor subtypes by antidepressants, antipsychotics and 5-HT(2) antagonists is reviewed. The possible mechanisms of this paradoxical down-regulation are discussed, and a new hypothesis on possible heterologous regulation of 5-HT(2A) receptors is proposed.
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Affiliation(s)
- Dirk Van Oekelen
- Johnson and Johnson Pharmaceutical, p/a Janssen Pharmaceutica, Turnhoutseweg 30, B-2340 Beerse, Belgium
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37
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Van Oekelen D, Megens A, Meert T, Luyten WHML, Leysen JE. Role of 5-HT(2) receptors in the tryptamine-induced 5-HT syndrome in rats. Behav Pharmacol 2002; 13:313-8. [PMID: 12218512 DOI: 10.1097/00008877-200207000-00008] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We distinguished the functions of the different 5-hydroxytryptamine-2 (5-HT(2)) receptor (5-HT(2)R) subtypes in the tryptamine-induced 5-HT syndrome in rats using (1) the 5-HT(2A)R antagonist R93274 (N-[(3-p-fluorophenyl-1-propyl)-4-methyl-4-piperidinyl]-4-amino-5-iodo-2-methoxybenzamide), the 5-HT(2A/C)R antagonist R99647 (2-(dimethylaminomethyl)2,3,3a,8-tetrahydrodibenzo[c,f]isoxazolo[2,3-a]azepine), the 5-HT(2B/C)R antagonist SB-242084 (6-chloro-5-methyl-1-[[2-[(2-methyl-3-pyridyl)oxy]-5-pyridyl]carbamoyl]-indoline), and several 5-HT(2)R antagonists (ketanserin, risperidone, pipamperone and mianserin); and (2) chronic 5-HT(2)R activation by 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM). In contrast to SB-242084, the selective 5-HT(2A)R antagonist R93274 as well as the non-selective 5-HT(2A)R antagonists (R99647, ketanserin, risperidone, pipamperone and mianserin) significantly inhibited tryptamine-induced forepaw treading and tremors, and reversed peripherally mediated cyanosis into hyperaemia; only the 5-HT(2A/C)R antagonists R99647 and mianserin inhibited the tryptamine-induced hunched back. Intermittent DOM administration (intravenously every 48 h for 12 days) did not change the centrally mediated tryptamine-induced forepaw treading, tremors and hunched back at 1, 4 or 7 days after the last DOM pretreatment. The DOM-induced head twitch response, measured immediately after every DOM injection, was not affected. In contrast, peripherally mediated cyanosis was reversed into hyperaemia in 75, 11 and 20% of all pretreated rats at 1, 4 and 7 days, respectively, after the last DOM administration. Taken together, these finding suggest that central 5-HT(2A)Rs mediate tryptamine-induced forepaw treading and tremors, that peripheral 5-HT Rs mediate tryptamine-induced cyanosis, and that 5-HT(2A)Rs mediate tryptamine-induced hunched back. Peripheral 5-HT(2C)Rs are more sensitive to desensitization after intermittent treatment with an agonist than central 5-HT(2A)Rs.
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MESH Headings
- DOM 2,5-Dimethoxy-4-Methylamphetamine/pharmacology
- Animals
- Behavior, Animal/drug effects
- Behavior, Animal/physiology
- Brain/drug effects
- Brain/metabolism
- Male
- Rats
- Rats, Wistar
- Receptor, Serotonin, 5-HT2A
- Receptor, Serotonin, 5-HT2B
- Receptor, Serotonin, 5-HT2C
- Receptors, Serotonin/drug effects
- Receptors, Serotonin/metabolism
- Serotonin Antagonists/administration & dosage
- Serotonin Antagonists/pharmacology
- Serotonin Receptor Agonists/pharmacology
- Serotonin Syndrome/chemically induced
- Serotonin Syndrome/metabolism
- Tryptamines
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Affiliation(s)
- D Van Oekelen
- Discovery Research, Janssen Research Foundation, Beerse, Belgium
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38
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Gray JA, Roth BL. Paradoxical trafficking and regulation of 5-HT(2A) receptors by agonists and antagonists. Brain Res Bull 2001; 56:441-51. [PMID: 11750789 DOI: 10.1016/s0361-9230(01)00623-2] [Citation(s) in RCA: 210] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
5-Hydroxytryptamine(2A) (serotonin(2A), 5-HT(2A)) receptors are important for many physiologic processes including platelet aggregation, smooth muscle contraction, and the modulation of mood and perception. A large number of pharmaceutical agents mediate their actions, at least in part, by modulating the number and/or activity of 5-HT(2A) receptors. Drugs with action at 5-HT(2A) receptors are used in the treatment of many disorders, including schizophrenia, depression, and anxiety disorders. This review summarizes over two decades of research on the regulation of 5-HT(2A) receptors and provides a comprehensive review of numerous in vivo studies describing the paradoxical phenomenon of 5-HT(2A) receptor down-regulation by chronic treatment with antidepressants and antipsychotics. In addition, studies reporting antagonist-induced internalization of 5-HT(2A) receptors and other G protein-coupled receptors will be highlighted as a possible mechanism to explain this paradoxical down-regulation. Finally, a review of the cellular and molecular mechanisms that may be responsible for agonist-mediated desensitization and internalization of 5-HT(2A) receptors will be presented.
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Affiliation(s)
- J A Gray
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4935, USA
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39
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Oekelen DV, Jurzak M, Van de Wiel D, Van Hecke G, Luyten WH, Leysen JE. Different regulation of rat 5-HT(2A) and rat 5-HT(2C) receptors in NIH 3T3 cells upon exposure to 5-HT and pipamperone. Eur J Pharmacol 2001; 425:21-32. [PMID: 11672571 DOI: 10.1016/s0014-2999(01)01170-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The 5-HT(2A) and 5-HT(2C) receptors belong to the same subtype of the G-protein coupled receptor family and have several agonist and antagonist ligands in common. To gain more insight into the differences in the regulation of the two receptors, we studied the effect of agonist and antagonist pre-treatment on radioligand receptor binding and 5-HT-induced inositol phosphate formation on rat 5-HT(2A) and rat 5-HT(2C) receptors stable expressed in NIH 3T3 cells. We compared short (15 min) and prolonged (48 h) pre-treatment of the cells with the natural agonist, 5-HT and with the antagonist pipamperone, which can be readily washed out. The rat 5-HT(2C) receptor showed an agonist-induced down-regulation (decrease in B(max) of labelled agonist and antagonist binding) and desensitisation (decrease in 5-HT-induced inositol phosphate formation and potency of 5-HT). Antagonist pre-treatment induced an increase in rat 5-HT(2C) receptor-mediated inositol phosphate formation as well as increased agonist and antagonist radioligand binding. These findings are consistent with the classical model of G-protein coupled receptor regulation. In contrast, the rat 5-HT(2A) receptor expressed in the same host cell behaved differently, unlike the classical model. Pre-treatment with 5-HT for 15 min and 48 h did not change receptor levels measured by radioligand binding, but the signal transduction response (inositol phosphate formation) was significantly reduced. Pre-treatment with the antagonist pipamperone for 15 min and 48 h caused an increase in antagonist radioligand binding but a reduction in agonist radioligand binding and a decrease in inositol phosphate formation and potency of 5-HT. Hence, the rat 5-HT(2A) receptor apparently undergoes agonist desensitisation without down-regulation of the total receptor number. Antagonist pre-treatment causes a paradoxical desensitisation, possibly by uncoupling of the receptor from G-proteins. The uncoupled receptor does not bind 5-HT in the nanomolar range but retains its antagonist binding properties. Paradoxical antagonist-induced desensitisation of rat 5-HT(2A) receptors has also been observed in vivo.
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Affiliation(s)
- D V Oekelen
- Department of Biochemical Pharmacology, Janssen Pharmaceutica, Janssen Research Foundation, Turnhoutseweg 30, B-2340 Beerse, Belgium
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40
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Eckler JR, Greizerstein H, Rabin RA, Winter JC. A sensitive method for determining levels of [-]-2,5,-dimethoxy-4-methylamphetamine in the brain tissue. J Pharmacol Toxicol Methods 2001; 46:37-43. [PMID: 12164258 DOI: 10.1016/s1056-8719(02)00159-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
INTRODUCTION Indolamine and phenethylamine hallucinogens are drugs of abuse and, as well, mimic some aspects of idiopathic psychosis. To assist in investigating the mechanisms of action of (-)2,5-dimethoxy4-methylamphetamine ([-]-DOM), a member of the phenethylamine class of serotonergic hallucinogens, a sensitive and precise method for determining its levels in the brain tissue is required. METHODS We now describe a method for determining nanogram quantities of [-]-DOM in the rat brain tissue using D-amphetamine as an intemal standard. The method employs solvent extraction with toluene and derivatization with trifluoroacetic acid anhydride (TFAA) followed by analysis using gas chromatography-mass spectrometry (GS-MS) in the selective ion monitoring (SIM) mode. RESULTS With SIM detection, our overall recoveries were greater than 90%. The method was reliable in terms of within-day and between-day precision, accuracy, and linearity. The procedure was applied to animal subjects to determine the in vivo [-]-DOM brain levels following intraperitoneal (ip) administration. Our findings indicate that peak levels of [-]-DOM do not coincide with the 75-min pretreatment time established by drug-induced stimulus control. DISCUSSION This study demonstrates a sensitive and precise analytical method for the determination of [-]-DOM levels in the rat brain following systemic administration of behaviorally relevant doses.
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Affiliation(s)
- J R Eckler
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, 14214-3000, USA.
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Kurumaji A, Aihara O, Yamada S, Toru M. Increased DOI-induced head shakings in adult rats neonatally treated with MK-801. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2000; 124:125-7. [PMID: 11113520 DOI: 10.1016/s0165-3806(00)00107-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
We examined the effects of neonatal treatment with MK-801 on 1-(2, 5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI)-induced head shaking as well as [(3)H]ketanserin binding in adult rats. Neonatal rats were injected with MK-801 (0.25 mg/kg, s.c., twice daily) or with saline from postnatal days (PND) 7-18. At PND 60, a statistically significant increase in the frequency of head shaking induced by DOI (1.0 mg/kg, s.c.) was observed in the rats neonatally treated with MK-801, compared to saline-treated rats, without any change in the specific [(3)H]ketanserin binding in the frontal cortex. These results suggest that repeated NMDA receptor blockades during the critical period of brain development produce a long lasting hyper-responsiveness in the 5-HT(2A) receptor-mediated behavior, interfering with the development of neural circuits related to the behavior.
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Affiliation(s)
- A Kurumaji
- Department of Neuropsychiatry, Tokyo Medical and Dental University School of Medicine, 1-5-45 Yushima, Bunkyo-ku, 113-8519, Tokyo, Japan.
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42
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Antoniou K, Bekris S, Saranti M, Stathis P, Rimikis M, Papadopoulou-Daifoti Z. The effects of antipsychotic drugs on serotonergic activity in the rat hippocampus. Eur Neuropsychopharmacol 2000; 10:315-24. [PMID: 10974601 DOI: 10.1016/s0924-977x(00)00087-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The serotonergic activity in hippocampus was investigated following acute and chronic treatment with the antipsychotic drugs haloperidol and risperidone. Acute administration of risperidone, the serotonin(2) (5-HT(2)) receptor antagonist ketanserin, and the dopamine (DA)-D(2) receptor antagonist raclopride increased the 5-hydroxyindoleacetic acid/serotonin (5-HIAA/5-HT) ratio. In contrast, acute administration of haloperidol did not affect this ratio. Chronic administration of risperidone maintained the increased 5-HIAA/5-HT ratio; a challenge dose of risperidone after the chronic treatment and the subsequent washout period also maintained the increased ratio. Chronic administration of haloperidol as well as a challenge dose of haloperidol following chronic treatment did not affect the serotonergic activity in hippocampus. Administration of ketanserin or raclopride after chronic treatment and the washout period induced an additional increase in the 5-HIAA/5-HT ratio in risperidone-treated rats. Moreover, a challenge dose of ketanserin, but not raclopride, increased the 5-HIAA/5-HT ratio in haloperidol-treated rats. The present results indicate that acute and chronic treatment of haloperidol or risperidone modified serotonergic activity in the hippocampus in a different way. Moreover, the augmentation of serotonergic activity induced by risperidone did not seem to be solely related to dopaminergic or serotonergic properties and may be of particular relevance for the amelioration of schizophrenia symptoms.
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Affiliation(s)
- K Antoniou
- Department of Experimental Pharmacology, Medical School, University of Athens, Goudi Athens, Greece 11527
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43
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Winter JC, Filipink RA, Timineri D, Helsley SE, Rabin RA. The paradox of 5-methoxy-N,N-dimethyltryptamine: an indoleamine hallucinogen that induces stimulus control via 5-HT1A receptors. Pharmacol Biochem Behav 2000; 65:75-82. [PMID: 10638639 DOI: 10.1016/s0091-3057(99)00178-1] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Stimulus control was established in rats trained to discriminate either 5-methoxy-N,N-dimethyltryptamine (3 mg/kg) or (-)-2,5-dimethoxy-4-methylamphetamine (0.56 mg/kg) from saline. Tests of antagonism of stimulus control were conducted using the 5-HT1A antagonists (+/-)-pindolol and WAY-100635, and the 5-HT2 receptor antagonist pirenperone. In rats trained with 5-MeO-DMT, pindolol and WAY-100635 both produced a significant degree of antagonism of stimulus control, but pirenperone was much less effective. Likewise, the full generalization of 5-MeO-DMT to the selective 5-HT1A agonist [+/-]-8-hydroxy-dipropylaminotetralin was blocked by WAY-100635, but unaffected by pirenperone. In contrast, the partial generalization of 5-MeO-DMT to the 5-HT2 agonist DOM was completely antagonized by pirenperone, but was unaffected by WAY-100635. Similarly, in rats trained with (-)-DOM, pirenperone completely blocked stimulus control, but WAY-100635 was inactive. The results obtained in rats trained with (-)-DOM and tested with 5-MeO-DMT were more complex. Although the intraperitoneal route had been used for both training drugs, a significant degree of generalization of (-)-DOM to 5-MeO-DMT was seen only when the latter drug was administered subcutaneously. Furthermore, when the previously effective dose of pirenperone was given in combination with 5-MeO-DMT (s.c.), complete suppression of responding resulted. However, the combination of pirenperone and WAY-100635 given prior to 5-MeO-DMT restored responding in (-)-DOM-trained rats, and provided evidence of antagonism of the partial substitution of 5-MeO-DMT for (-)-DOM. The present data indicate that 5-MeO-DMT-induced stimulus control is mediated primarily by interactions with 5-HT1A receptors. In addition, however, the present findings suggest that 5-MeO-DMT induces a compound stimulus that includes an element mediated by interactions with a 5-HT2 receptors. The latter component is not essential for 5-MeO-DMT-induced stimulus control, but is revealed in animals tested or trained with a 5-HT2-selective agonist such as (-)-DOM. Based upon the present data, we conclude that 5-MeO-DMT differs from DOM with respect to the serotonergic element that mediates stimulus control in the rat, but that it shares with DOM a functionally significant interaction with 5-HT2 receptors.
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Affiliation(s)
- J C Winter
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, USA
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Abstract
The involvement of 5-HT2 receptor subtypes in mediating a contraction response in the isolated intestine of Suncus murinus was investigated using DOI ((+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-amino-propane, a 5-HT2 receptor agonist) which produced a bell-shaped concentration response curve that was significantly (p < 0.05) reduced by methysergide (a 5-HT1/2 receptor antagonist, 1 microM) but not ketanserin (a 5-HT2A receptor antagonist, 1 microM), yohimbine (a 5-HT2B receptor antagonist, 1 microM) or a combination of ondansetron (a 5-HT3 receptor antagonist, 1 microM) plus SB204070 (8-amino-7-chloro(N-butyl-4-piperidyl) methylbenzo-1,4-dioxan-5-carboxylate hydrochloride, a 5-HT4 receptor antagonist, 1 nM). The contraction response to the lower concentrations of DOI (10 nM-0.3 microM) was reduced in the presence of SB206553 (5-methyl-1-(3-pyridylcarbamoyl)-1,2,3,5-tetrahydropyrrolo[2 ,3-f]indole, a 5-HT2B/2C receptor antagonist, 1 microM), whilst conversely, the reducing response to the higher concentrations of DOI (1-30 microM) was prevented. A repeated challenge with 3 microM DOI produced a smaller response (desensitisation) and also reduced the response to 5-HT (5-hydroxytryptamine, 0.3 microM) that was inhibited by SB206553 (1 microM). Data indicate that 5-HT2C receptors are likely candidates to mediate the contractile response to DOI and demonstrate desensitisation to repeated challenges.
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Affiliation(s)
- F A Javid
- Postgraduate Studies in Pharmacology, Department of Pharmacology, The School of Pharmacy, University of Bradford, UK.
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Maćkowiak M, Chocyk A, Fijał K, Czyrak A, Wedzony K. c-Fos proteins, induced by the serotonin receptor agonist DOI, are not expressed in 5-HT2A positive cortical neurons. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1999; 71:358-63. [PMID: 10521592 DOI: 10.1016/s0169-328x(99)00195-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In the present study, we tried to find out whether the expression of c-Fos proteins induced by DOI, an agonist of 5-HT2A/2C receptor subtypes is colocalized with 5-HT2A receptor protein in cortical neurons. 5-HT2A receptor protein was found in two major neuronal elements: dendritic processes (seen in layers II/III-V) and less abundantly in cell bodies (layer V). In our experiment, DOI (8 mg/kg) induced a robust appearance of c-Fos proteins mainly in neuronal nuclei of the upper part of layer V/IV, and a moderate amount of sparsely distributed nuclei in deep cortical layers (V and VI). It was found that c-Fos proteins never occurred in cortical neurons, which were immunopositive for the presence of 5-HT2A receptor protein. It is concluded that the induction of c-Fos proteins expression by DOI though initiated by activation of 5-HT2A receptors, requires the involvement of intermediate neurotransmitter(s). Additionally, our study indicates that the appearance of DOI-induced c-Fos proteins cannot be used as a simple and direct marker of localization and site of activation of 5-HT2A receptors.
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Affiliation(s)
- M Maćkowiak
- Institute of Pharmacology, Polish Academy of Sciences, 31-343, Kraków, Poland
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46
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Arvanov VL, Liang X, Magro P, Roberts R, Wang RY. A pre- and postsynaptic modulatory action of 5-HT and the 5-HT2A, 2C receptor agonist DOB on NMDA-evoked responses in the rat medial prefrontal cortex. Eur J Neurosci 1999; 11:2917-34. [PMID: 10457188 DOI: 10.1046/j.1460-9568.1999.00708.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Intracellular recordings were made from pyramidal neurons in layers V and VI of the rat medial prefrontal cortex in slice preparations to investigate the effect of the serotonin 5-HT2A,2C receptor agonist (-)-1-2,5-dimethoxy-4-bromophenol-2-aminopropane (DOB) and 5-hydroxytryptamine (5-HT) on N-methyl-D-aspartate (NMDA)-induced responses. Bath application of either DOB or 5-HT [in the presence of antagonists to 5-HT1A, 5-HT3 and gamma-aminobutytric acid (GABA) receptors] produced a concentration-dependent biphasic modulation of the NMDA responses. They facilitated and inhibited NMDA responses at low (</= 1 microM DOB and </= 50 microM 5-HT) and higher concentrations, respectively. Both the facilitating and inhibitory action were blocked by the highly selective 5-HT2A receptor antagonist R-(+)-alpha-(2, 3-dimethoxyphenil)-1-[4-fluorophenylethyl]-4-piperidineme thanol (M100907) and the 5-HT2 receptor antagonist ketanserin, thus indicating that both facilitation and inhibition were mediated by the activation of the 5-HT2A receptor subtype. However, the facilitating, but not inhibitory, action of DOB showed a marked desensitization, suggesting that the facilitation and inhibition of NMDA responses resulted from activation of different 5-HT2A receptor subtypes and/or signal-transduction pathways. Indeed, the selective PKC inhibitor chelerythrine and the Ca2+/CaM-KII inhibitor KN-93 prevented the facilitating and inhibitory action of DOB, respectively. We have generated several lines of evidence to indicate the following scenario. Low concentrations of DOB, at presynaptic nerve terminals, markedly enhance NMDA-induced release of excitatory amino acids (EAAs), which then act upon both NMDA and non-NMDA receptors to elicit inward current. The massive inward current masks the postsynaptic inhibitory action of DOB. At higher concentrations, DOB inhibits the release of EAAs and discloses the postsynaptic inhibitory action.
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Affiliation(s)
- V L Arvanov
- Department of Psychiatry and Behavioral Science, SUNY at Stony Brook, 11794-8790, USA
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47
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Kulikov A, Moreau X, Jeanningros R. Effects of experimental hypothyroidism on 5-HT1A, 5-HT2A receptors, 5-HT uptake sites and tryptophan hydroxylase activity in mature rat brain1. Neuroendocrinology 1999; 69:453-9. [PMID: 10364698 DOI: 10.1159/000054449] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The study was aimed at investigating the repercussions of deficiency in thyroid function with and without thyroid hormone (TH) replacement on the neurochemical entities which underly serotonin (5-HT) neutrotransmission, namely 5-HT1A, 5-HT2A receptors, 5-HT transporter and tryptophan hydroxylase (TPH) in the mature brain. Surgically thyroidectomized male Wistar rats received: (1) an iodine-free diet to produce severe hypothyroidism; (2) hormonal replacement with 15 microgram/kg/day of thyroxine (T4) for 21 days to normalize serum TH levels, or (3) hormonal replacement with 200 microgram/kg/day of T4 for 14 days to produce an excess of circulating THs. Sham-operated rats were used as controls. Neither hypothyroidism nor an excess in serum TH levels affected 3H-8-OH-DPAT binding to 5-HT1A receptors, 3H-citalopram binding to 5-HT transporter and TPH activity in various brain structures indicating that, in the mature brain, the presynaptic entities of 5-HT neurotransmission are resistant to large variations in TH levels. By contrast, hypothyroid rats had a significant decrease in Bmax of 3H-ketanserin binding to cortical 5-HT2A receptors compared to controls. Cortical 3H-ketanserin binding in thyroidectomized rats was normalized after replacement with low-dose T4. Excess serum TH levels in thyroidectomized rats did not produce any changes in cortical 5-HT2A receptors when compared to thyroidectomized rats with normalized TH levels. The present data suggest that the decrease in cortical 5-HT2A receptors is the main neurochemical event underlying the impairing effect of hypothyroidism on 5-HT neurotransmission.
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Affiliation(s)
- A Kulikov
- INSERM U38, Fonction Thyroïdienne et Régulations, Marseille, France
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Briddon SJ, Leslie RA, Elliott JM. Comparative desensitization of the human 5-HT2A and 5-HT2C receptors expressed in the human neuroblastoma cell line SH-SY5Y. Br J Pharmacol 1998; 125:727-34. [PMID: 9831908 PMCID: PMC1571005 DOI: 10.1038/sj.bjp.0702145] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. We have used previously characterized clones of the human neuroblastoma cell line, SH-SY5Y. constitutively expressing either the human 5-HT2A or 5-HT2C receptor to compare their desensitization profiles after exposure to 5-HT. 2. 5-HT stimulated [3H]-inositol phosphate ([3H]-IPx) production at both the 5-HT2C (pEC50=8.03+/-0.15) and 5-HT2A receptors (pEC50=7.15+/-0.08), with maximal responses occurring after exposure to 1 microM and 10 microM 5-HT, respectively. 3. Exposure of cells to maximally effective concentrations of 5-HT caused time- and concentration-dependent desensitization of [3H]-IPx formation. The 5-HT2A response desensitized slower (t1/2 = 110 min) and with lower sensitivity than that of the 5-HT2C receptor (t1/2 = 12.5 min). In each case, desensitization was blocked by co-administration of a specific receptor antagonist. Following exposure to 10 microM 5-HT for 2 h, both receptors exhibited extensive desensitization, with subsequent responses to 5-HT reduced by more than 80%. 4. 5-HT stimulated Ins(1,4,5)P3 production with a potency similar to that for [3H]-IPx production at each receptor. In both cases Ins(1,4,5)P3 levels peaked rapidly then returned to basal level within a short time. This peak consistently occurred earlier for the 5-HT2C receptor (5 s) than for the 5-HT2A receptor (20 s). 5. Prior exposure of SH-SY5Y/5-HT2C cells to 5-HT (1 microM/15 min) caused a significant decrease in the 5-HT-stimulated peak in Ins(1,4,5)P3 levels whereas no such change occurred in SH-SY5Y/5-HT2A cells following exposure to 10 microM 5-HT for 15 min. 6 These results indicate that the human 5-HT2A and 5-HT2C receptors both exhibit desensitization at the level of inositol phosphate formation when expressed in the same cellular environment, with the 5-HT2C receptor being more sensitive to 5-HT-mediated desensitization than the 5-HT2A receptor.
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Affiliation(s)
- S J Briddon
- Oxford-University Smith Kline Beecham Centre for Applied Neuropsychobiology, Radcliffe Infirmary
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Roth BL, Willins DL, Kroeze WK. G protein-coupled receptor (GPCR) trafficking in the central nervous system: relevance for drugs of abuse. Drug Alcohol Depend 1998; 51:73-85. [PMID: 9716931 DOI: 10.1016/s0376-8716(98)00067-2] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- B L Roth
- Department of Psychiatry, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4935, USA.
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Fone KC, Austin RH, Topham IA, Kennett GA, Punhani T. Effect of chronic m-CPP on locomotion, hypophagia, plasma corticosterone and 5-HT2C receptor levels in the rat. Br J Pharmacol 1998; 123:1707-15. [PMID: 9605579 PMCID: PMC1565342 DOI: 10.1038/sj.bjp.0701798] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
1. The present study examined 5-HT2C receptor agonist-induced behavioural tolerance and 5-HT2C receptor down-regulation in adult rat brain. The effect of chronic subcutaneous infusion of the 5-HT2C receptor agonist, m-chlorophenylpiperazine (m-CPP, 10 mg kg(-1), day(-1)), for 14 days was examined on daily food intake, the ability of acute m-CPP (2.5 mg kg(-1), i.p.) to induce hypolocomotion in a novel arena and elevate plasma corticosterone levels and on ex vivo cortical [3H]-mesulergine binding and hippocampal 5-HT2C receptor protein levels. 2. Before chronic infusion, m-CPP (2.5 mg kg(-1), i.p.) attenuated the number of turns and rears made in a novel open field arena. In contrast, while m-CPP still elicited this hypolocomotion following 14 days, saline infusion, no such hypolocomotion occurred in rats given chronic m-CPP (10 mg kg(-1) day(-1)), indicating that almost complete tachyphylaxis of this behaviour occurred with chronic 5-HT2C receptor agonist injection. 3. During chronic infusion of m-CPP, rats consumed less food per day than saline-treated controls. Acute challenge with m-CPP following two weeks, treatment still attenuated food intake over the next four hours (by 43% and 30%, respectively from that on the previous day) in saline and m-CPP infusion groups, showing that only partial tolerance to 5-HT2C receptor agonist-induced hypophagia occurred. 4. In naive home cage rats, plasma corticosterone was elevated in a dose-dependent manner 35 min after m-CPP injection (0.5, 1 and 3 mg kg(-1), i.p.) but levels were comparable to control values 16 h after m-CPP (2, 5 and 10 mg kg(-1), i.p.). Sixteen hours after a single m-CPP injection (2.5 mg kg(-1), i.p.), plasma corticosterone levels were comparable in a group of rats which had received 14 days infusion of m-CPP or saline. However, following a similar acute m-CPP injection (2.5 mg kg(-1), i.p., - 16 h) in rats previously infused for 14 days with m-CPP, plasma corticosterone levels were lower than those in a separate group which received no chronic infusions (but only acute m-CPP injection), even though the plasma m-CPP levels were comparable in both groups. The data are consistent with the proposal that chronic m-CPP induced some down-regulation of hypothalamic 5-HT2C receptors which contribute, in a tonic manner, to plasma corticosterone secretion under the conditions investigated. 5. Chronic m-CPP infusion reduced the amount of [3H]-mesulergine binding (by 27%, without altering the KD) in membranes prepared from parietal/occipital/temporal cortex (under conditions to exclude binding to 5-HT2A receptors) and 5-HT2C receptor protein-like immunoreactive levels measured by radioimmunoassay in the hippocampus by 38%, confirming that 5-HT2C receptor down-regulation had occurred. 6. Even after 14 days m-CPP infusion only partial behavioural tolerance and 5-HT2C receptor down-regulation were observed, which may vary in different brain regions of the rat. Thus the hypophagia produced by m-CPP may involve activation of 5-HT2C receptors in the hypothalamus, where there is a greater receptor reserve or which are more resistant to agonist-induced down-regulation than 5-HT2C receptors in limbic areas (striatum and nucleus accumbens) mediating m-CPP-induced hypolocomotion.
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Affiliation(s)
- K C Fone
- School of Biomedical Sciences, University of Nottingham, Queen's Medical Centre
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