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Maguire DR. Effects of 2,5-Dimethoxy-4-Methylamphetamine (DOM) and 2-Piperazin-1-yl-Quinoline (Quipazine) on Fentanyl Versus Food Choice in Rhesus Monkeys. J Pharmacol Exp Ther 2023; 384:155-162. [PMID: 36272734 PMCID: PMC9827501 DOI: 10.1124/jpet.122.001318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 08/18/2022] [Accepted: 10/03/2022] [Indexed: 11/06/2022] Open
Abstract
There has been increasing interest in the potential therapeutic effects of drugs with agonist properties at serotonin 2A subtype (5-HT2A) receptors (e.g., psychedelics), including treatment of substance use disorders. Studying interactions between 5-HT2A receptor agonists and other drugs is important for understanding potential therapeutic effects as well as adverse interactions. Direct-acting 5-HT2A receptor agonists such as 2,5-dimethoxy-4-methylamphetamine (DOM) and 2-piperazin-1-yl-quinoline (quipazine) enhance some (e.g., antinociceptive) effects of opioids; however, it is unclear whether they alter the abuse-related effects of opioids. This study examined whether DOM and quipazine alter the reinforcing effects of fentanyl in rhesus monkeys (n = 6) responding under a food versus drug choice procedure. Responding on one lever delivered sucrose pellets and responding on the other lever delivered intravenous (i.v.) infusions. In one set of experiments, fentanyl (0.1-3.2 µg/kg/infusion) versus food choice sessions were preceded by noncontingent i.v. pretreatments with DOM (0032-0.32 mg/kg), quipazine (0.32-1.0 mg/kg), naltrexone (0.032 mg/kg), or heroin (0.1 mg/kg). In another set of experiments, fentanyl was available during choice sessions in combination with DOM (0.32-100 µg/kg/infusion) or quipazine (3.2-320 µg/kg/infusion) in varying dose ratios. Naltrexone decreased and heroin increased fentanyl choice, demonstrating sensitivity of responding to pharmacological manipulation. However, whether given as a pretreatment or made available in combination with fentanyl as a mixture, neither DOM nor quipazine significantly altered fentanyl choice. These results suggest that 5-HT2A receptor agonists do not enhance the reinforcing effects of opioids and, thus, will not likely enhance abuse potential. SIGNIFICANCE STATEMENT: Serotonin 2A subtype receptor agonists enhance some (e.g., antinociceptive) effects of opioids, suggesting they could be combined with opioids in some therapeutic contexts such as treating pain. However, it is unclear whether they also enhance adverse effects of opioids, including abuse. Results of this study indicate that serotonin 2A subtype receptor agonists do not reliably enhance opioid self-administration and, thus, are unlikely to enhance the abuse potential of opioids.
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Affiliation(s)
- David R Maguire
- Department of Pharmacology and Addiction Research, Treatment & Training Center of Excellence, University of Texas Health Science Center at San Antonio, San Antonio, Texas
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2
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McCreary AC, Filip M, Cunningham KA. Discriminative stimulus properties of (+/-)-fenfluramine: the role of 5-HT2 receptor subtypes. Behav Neurosci 2003; 117:212-21. [PMID: 12708517 DOI: 10.1037/0735-7044.117.2.212] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The role of serotonin 5-HT2 receptors (5-HT2R) in the discriminative stimulus effects of fenfluramine was investigated. Male Sprague-Dawley rats were trained to discriminate (+/-)-fenfluramine (2 mg/kg ip) from saline using a 2-lever, water-reinforced paradigm. Drug-lever responding after fenfluramine was dose-dependent. The 5-HT(2C/1B)R agonist mCPP and the 5-HT(2C)R agonist MK 212 fully substituted, whereas the 5-HT(2A/2C)R agonist DOI partially substituted, for the training drug. The 5-HT(2B)R agonist BW 723C86 engendered saline-lever responding. The 5-HT(2C/2B)R antagonist SB 206553 completely antagonized the fenfluramine discrimination a well as the full substitutions of mCPP and MK 212 and the partial substitution of DOI. The selective 5-HT(2A)R antagonist M100907 partially suppressed the stimulus effects of fenfluramine, mCPP, and MK 212 and almost fully attenuated the partial substitution of DOI. RS 102221, a selective 5-HT(2C)R antagonist that does not cross the blood-brain barrier, did not alter the fenfluramine cue. Results demonstrate that the discriminative stimulus effects of fenfluramine are centrally mediated by 5-HT(2C)R and to some extent by 5-HT(2A)R.
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Affiliation(s)
- Andrew C McCreary
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston 77555, USA
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3
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Callahan PM, Cunningham KA. Involvement of 5-HT2C receptors in mediating the discriminative stimulus properties of m-chlorophenylpiperazine (mCPP). Eur J Pharmacol 1994; 257:27-38. [PMID: 8082704 DOI: 10.1016/0014-2999(94)90690-4] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Rats were trained to discriminate the 5-HT receptor agonist m-chlorophenylpiperazine (mCPP; 1 mg/kg) from saline using a two-lever, water-reinforced drug discrimination task. The antidepressant trazodone (1-8 mg/kg), the 5-HT1B/2C receptor agonists 1-(m-trifluoromethylphenyl)piperazine (TFMPP; 0.25-1 mg/kg) and MK 212 (0.125-1 mg/kg), and the mixed 5-HT1A/B receptor agonist RU 24969 (0.25-2 mg/kg) substituted fully for mCPP. The 5-HT2A/2C receptor agonists 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI; 0.25-1 mg/kg) and d-lysergic acid diethylamide (LSD; 0.02-0.08 mg/kg) and the 5-HT releaser fenfluramine (0.5-2 mg/kg) also mimicked mCPP. Agonists selective for the 5-HT1A or 5-HT3 receptor or the 5-HT reuptake site produced saline-lever responding. The ergoline derivative mesulergine (0.5-4 mg/kg) produced a partial agonist/antagonist profile. The 5-HT1/2 receptor antagonist metergoline (0.125-1 mg/kg) completely blocked the mCPP cue whereas the 5-HT2A/2C receptor antagonists ketanserin and LY 53857 as well as all other 5-HT receptor antagonists failed to block the mCPP cue. The dopamine receptor antagonists SCH 23390 and haloperidol were also ineffective mCPP antagonists. Following pretreatment with the 5-HT synthesis inhibitor p-chlorophenylalanine (pCPA; 100 mg/kg/day) for 3 consecutive days, the discriminability of low doses of mCPP increased, whereas the effects of fenfluramine decreased. The present results suggest that the discriminative stimulus effects of mCPP in rats are mediated primarily by postsynaptic 5-HT2C receptors.
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Affiliation(s)
- P M Callahan
- University of Texas Medical Branch, Department of Pharmacology and Toxicology, Galveston 77555-1031
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4
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Boja JW, Schechter MD. Possible serotonergic and dopaminergic mediation of the N-ethyl-3,4-methylenedioxyamphetamine discriminative stimulus. Eur J Pharmacol 1991; 202:347-53. [PMID: 1684158 DOI: 10.1016/0014-2999(91)90277-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Eight male rats previously trained to discriminate 2.0 mg/kg N-ethyl-3,4-methylenedioxyamphetamine (MDE) from its vehicle in a two-lever, food motivated task were utilized to characterize the stimulus properties of MDE. The 5-HT receptor agonists 1-(m-trifluoromethylphenyl)piperazine (TFMPP), quipazine and 6-methoxy-1,2,3,4 tetrahydro-beta-carboline were able to generalize to the stimulus produced by MDE. However, the 5-HT receptor agonists m-chlorophenylpiperazine (mCPP), buspirone and norfenfluramine, the dopamine receptor agonist amphetamine, as well as the acetylcholine receptor agonist arecoline did not completely generalize. In addition, the simultaneous administration of norfenfluramine and amphetamine generalized to MDE. Pretreatment with the serotonin receptor antagonists cinanserin and metergoline or the dopamine receptor antagonist haloperidol failed to completely inhibit the discriminative stimulus produced by MDE. Multiple p-chlorophenylalanine (PCPA) pretreatments significantly reduced MDE discrimination, whereas vehicle discrimination was unaffected. Five days following cessation of PCPA pretreatment, MDE discrimination returned to criterion levels and remained at that level. These results suggest that the stimulus produced by MDE involve a complex interaction of various neurotransmitters, with both serotonergic and dopaminergic components.
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Affiliation(s)
- J W Boja
- Department of Pharmacology, Northeastern Ohio Universities College of Medicine, Rootstown 44272
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5
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Schechter MD. Effect of serotonin depletion by p-chlorophenylalanine upon discriminative behaviours. GENERAL PHARMACOLOGY 1991; 22:889-93. [PMID: 1684770 DOI: 10.1016/0306-3623(91)90226-v] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
1. Para-chlorophenylalanine (p-CPA), a competitive inhibitor of the serotonin (5-HT) synthesis enzyme tryptophan hydroxylase, was administered to rats at a dosage (100 mg/kg daily for 3 days) that depletes 5-HT. 2. Different groups of these rats were previously trained to discriminate the interoceptive stimuli produced by amphetamine, cathinone, 3,4-methylenedioxymethamphetamine (MDMA), N-ethyl-3,4-methylenedioxyamphetamine (MDE), fenfluramine or yohimbine, and the effect of p-CPA pretreatment upon their discriminative performance was compared with the effect of saline (control) pretreatment. 3. p-CPA was shown to have no effect upon the dopaminergically-mediated stimuli produced by the stimulants amphetamine and cathinone or upon yohimbine performance. 4. p-CPA significantly decreased discriminative performance with the serotonergic releasing drugs MDMA, MDE and fenfluramine. This decrease in discriminative performance returned to pre-p-CPA (criterion) levels at a time (9-12 days) when 5-HT has been reported to replete to normal brain concentrations. 5. It is concluded that p-CPA pretreatment lowers brain 5-HT and, in turn, significantly decreases the ability of rats to discriminate centrally active drugs whose interoceptive cueing stimuli are mediated by 5-HT neurons.
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Affiliation(s)
- M D Schechter
- Department of Pharmacology, Northeastern Ohio Universities College of Medicine, Rootstown 44272
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6
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Abstract
Systemically administered serotonin, which does not pass the blood-brain barrier, inhibited nipple attachment behavior in 20- and 30-day-old rat pups. Xylamidine, a peripheral serotonin antagonist, attenuated the effects of serotonin, quipazine, and fenfluramine on nipple attachment behavior. Thus, serotonin receptors in the periphery may play an important role in the serotonergic inhibitory mechanism that has been hypothesized as the developing system leading to weaning. However, unlike more general 5-HT antagonists, xylamidine given alone failed to facilitate suckling, suggesting different sites of action for facilitation and inhibition of this infantile behavior.
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Affiliation(s)
- S T Bateman
- Department of Psychology, Dartmouth College, Hanover, NH 03755
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7
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Abstract
Both normal and genetically dystonic (dt) rats show a high-frequency forepaw tremor in response to systemic administration of the serotonin (5-HT) agonist quipazine at 8 days of age. The response declines with age in normal, but not dystonic, rats. By 16 days of age and after the development of a generalized movement disorder, the dystonic rat exhibits enhanced sensitivity to the tremorogenic effects of the drug in comparison with normal rats. Tremor was blocked by pretreatment with ketanserin, suggesting that it is mediated by 5-HT2 receptors. The dystonic rat has previously been shown to be insensitive to the tremorogenic effects of harmaline, a drug presumed to act indirectly through serotonergic neurons. This finding, coupled with the increased sensitivity to quipazine, suggests the presence of an abnormality in serotonergic systems in the mutants. Since there is evidence of abnormality in the olivo-cerebellar system in the dystonic rat, the alternative hypothesis that a nonserotonergic defect in the olivo-cerebellar system accounts for both the failure of behavioral response to harmaline and the persistent expression of a response to quipazine is also discussed.
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Affiliation(s)
- V L Michela
- Department of Psychology, University of Alabama, Birmingham 35294
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8
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Evans SM, Zacny JP, Johanson CE. Three-choice discrimination among (+)-amphetamine, fenfluramine and saline in pigeons. Pharmacol Biochem Behav 1990; 35:971-80. [PMID: 1971722 DOI: 10.1016/0091-3057(90)90387-w] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Five pigeons were trained to discriminate among (+)-amphetamine (AMPH; 1.7 or 3.0 mg/kg), fenfluramine (FEN; 5.6 or 10 mg/kg), and saline using a three-choice drug discrimination procedure. The results of the study demonstrated that a reliable discrimination between AMPH and FEN could be obtained and the discriminative stimulus (DS) effects of these two drugs did not overlap, i.e., were mutually exclusive. Phenmetrazine produced a dose-related increase in AMPH-appropriate responding with no responding occurring on the FEN-appropriate key. Two serotonin agonists, quipazine (5-HT2) and MK 212 (5-HT1), produced FEN-appropriate responding in two of three pigeons, while a third pigeon responded predominantly on the AMPH-appropriate key following their administration. In contrast, phencyclidine produced predominantly (greater than 50%) saline-appropriate responding, indicating that the DS effect of phencyclidine was unlike either AMPH or FEN. Finally, compounds known to have multiple DS properties such as MDA and MDMA were tested. The results with these compounds confirmed that these drugs have complex DS effects both within and across individual pigeons.
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Affiliation(s)
- S M Evans
- Department of Psychiatry, Pritzker School of Medicine, University of Chicago, IL 60637
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9
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Abstract
The effect of SCH 23390 administration on the serotonin system-dependent head twitch behavior was studied in the rat. A small dose of SCH 23390 (1.25 micrograms/kg), injected 20 min before the test, decreased the number of quipazine-induced head twitches. Repeated treatment with SCH 23390 (0.5 mg/kg, SC), once a day for 18 days, increased the number of spontaneously occurring and quipazine-induced head twitches. The enhancing effect of repeated administration of SCH 23390 was blocked by cyproheptadine (0.4 mg/kg). The results indicate that acute injection of SCH 23390 blocks central serotonin receptors, whereas repeated treatment induces their functional supersensitivity.
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Affiliation(s)
- M Bijak
- Polish Academy of Sciences, Institute of Pharmacology, Kraków
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10
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Abstract
Various direct- and indirect-acting serotonin (5-HT) agonists serve as training drugs in tests of stimulus control of behavior; such agents include: 5-hydroxytryptophan, 5-methoxy-N,N-dimethyltryptamine, and fenfluramine. However, with the recent discovery of multiple populations of central 5-HT binding sites, the concept of site-selective serotonergic agents needs to be addressed. Certain 4-substituted 1-(2,5-dimethoxyphenyl)-2-aminopropanes such as DOM (4-methyl), DOB (4-bromo), and DOI (4-iodo) appear to be 5-HT2-selective agonists and serve as effective training drugs in rats. Stimulus generalization occurs among these agents regardless of which is used as the training drug, although stimulus generalization does not occur with 5-HT1A-selective agonists [e.g., 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH DPAT)] or with 5-HT1B-selective agonists [e.g., 1-(3-trifluoromethylphenyl)piperazine (TFMPP)]. 8-OH DPAT and TFMPP also serve as training drugs; the 8-OH DPAT-stimulus generalizes to other 5-HT1A agonists, but not to 5-HT1B or 5-HT2 agonists, whereas the TFMPP-stimulus generalizes to other 5-HT1B agonists, but not to 5-HT1A or 5-HT2 agonists. Classical serotonin antagonists, most of which are rather selective for 5-HT2 sites, and 5-HT2-selective antagonists are able to block the stimulus effects of DOM, DOB, and DOI, but not those of 8-OH DPAT or TFMPP. The results of such studies reveal that, in rats, site-selective 5-HT agonists produce stimulus effects that are also selective; although generalization may occur with nonselective 5-HT agonists, animals trained to discriminate site-selective 5-HT agonists apparently do not recognize other 5-HT agonists that are selective for a different site. Animals trained to discriminate such agents from saline might be useful for the identification and/or investigation of novel site-selective agonists and antagonists (for example, the 8-OH DPAT-stimulus generalizes to members of a new class of anxiolytics that display high affinity for 5-HT1A binding sites), and might also aid in the overall understanding of central serotonergic mechanisms.
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Affiliation(s)
- R A Glennon
- Department of Medicinal Chemistry, School of Pharmacy, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298
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11
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Rauch RJ, Stolerman IP. Midazolam cue in rats: effects of drugs acting on GABA and 5-hydroxytryptamine systems, anticonvulsants and sedatives. J Psychopharmacol 1987; 1:71-80. [PMID: 22158887 DOI: 10.1177/026988118700100203] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The discriminative stimulus effect of midazolam, a short-acting benzodiazepine, was used for testing the effects of related drugs including agents thought to act at different sites in the proposed benzodiazepine receptor complex. Rats were trained in a standard two- bar operant conditioning procedure with food reinforcers delivered on a tandem schedule. The 0.4 mg/kg dose of midazolam used for training was well discriminated, typically yielding about 95% correct responding. There was no generalization to the GABA agonists muscimol and THIP, to the 5-HT antagonists cyproheptadine and methergoline, to buspirone, CGS 9896, ethanol, Ro 5-4864, promethazine, phenytoin sodium or sodium valproate. Muscimol and THIP also failed to potentiate the effects of midazolam. The GABA antagonist bicuculline weakly attenuated the discriminative effect of midazolam without impairing generalization to pentobarbitone, whereas the benzodiazepine inverse agonist FG 7142 did not attenuate the effect of midazolam. The results provide additional evidence for the notable specificity of the midazolam cue but do little to link the behavioural effects of benzodiazepines to GABA or 5- HT systems. Perhaps the potency, efficacy or selectivity of the GABA agonists was inadequate to produce the expected results. Only the effects of bicuculline, and those reported previously for picrotoxin, provided some support for the hypothesis that midazolam cue is mediated by the GABA system.
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Affiliation(s)
- R J Rauch
- Departments of Pharmacology and Psychiatry, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, UK
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12
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Abstract
This review discusses the effects of antidepressant drugs on behaviors that are changed during the clinical treatment of depression. We first consider whether there is a similar subjective state produced by antidepressant drugs that might be akin to the mood changes caused clinically by these drugs. We thus review the evidence that antidepressant drugs can produce a distinctive enough subjective state to serve as a discriminative stimulus, and then discuss the nature of the cue produced. Secondly, we discuss whether there is any evidence that antidepressants enhance the rewarding aspects of stimuli since this aspect of behavior is reported to change during the successful treatment of depression. In this section we review the effects on electrical brain stimulation, water and food intake, exploratory and social behaviors. Finally, because of the proposed role of stress in the aetiology of depression, we review the effects of antidepressants on the responses to acute and chronic stress.
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Trulson ME. Dissociations between the effects of hallucinogens on behavior and raphe unit activity in behaving cats. Pharmacol Biochem Behav 1986; 24:351-7. [PMID: 3952126 DOI: 10.1016/0091-3057(86)90365-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The hypothesis that hallucinogenic drugs exert their behavioral effects by an action at pre- or postsynaptic serotonin receptors was evaluated by co-administering various drugs that possess either serotonin agonist or antagonist properties, while concurrently monitoring behavior and the electrophysiological activity of serotonin-containing dorsal and median raphe neurons in freely moving cats. Co-administration of the serotonin receptor blockers, metergoline or mianserin, with lysergic acid diethylamide (LSD) produced no change in the inhibitory effects of LSD on raphe neurons, but produced a dose-dependent blockade of the behavioral effects of LSD in the cat. The latter data suggest that perhaps LSD exerts its behavioral effects by an action at postsynaptic serotonin receptors. Co-administration of drugs that increase synaptic serotonin, L-5-hydroxytryptophan, tranylcypromine, fluoxetine or p-chloramphetamine with LSD greatly potentiated the inhibitory effect of LSD on raphe unit activity, but also produced dose-dependent decreases in these behavioral effects of LSD in the cat. Thus, both enhancing the activity at postsynaptic serotonin receptors and receptor antagonism blocked the behavioral effects of LSD. Co-administration of dopamine receptor blockers, haloperidol or chlorpromazine, produced no significant change in the response of raphe neurons to LSD, but these drugs also produced a dose-dependent blockade of the behavioral effects of LSD in the cat. Co-administration of the dopamine agonists, apomorphine or d-amphetamine, however, potentiated the behavioral effects of LSD, while producing a partial reversal of the inhibitory effects of LSD on raphe unit activity. The results are discussed in the context of using animal models to study the possible actions of hallucinogens in humans.
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14
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Abstract
This review compares the effects of LSD and its nonhallucinogenic congener lisuride hydrogen maleate (LHM) on various biochemical, behavioral and electrophysiological indices of neuronal function. The underlying rationale is that any differences between the effects of LSD and LHM might be relevant to neuronal actions which are unique and specific to hallucinogenic drugs and thereby provide clues to the neurobiological substrates of hallucinogenesis. In biochemical studies, LHM appears to be very similar to LSD with respect to its actions on monoaminergic (5-HT, DA, NE) systems. The major difference between the two ergots appears quantitative in nature since LHM is more potent than LSD, especially on DA neurochemistry. Needed at the present time are additional comparative studies of LSD and LHM with respect to other biochemical measures, for example on the release of 5-HT and DA and comparisons at more molecular levels such as subcellular compartmentation. Also necessary are more intensive regional analyses on specific subpopulations of 5-HT and DA systems (mesolimbic, mesostriatal and mesocortical). Behavioral studies are relatively uniform in their characterization of the greater DA-ergic activity of LHM as compared to LSD. In particular, the drug discrimination (DD) procedure has indicated a more specific interaction of LSD with 5-HT neuronal systems as compared to LHM and has successfully differentiated the relative roles of 5-HT and DA systems in the behavioral effects of LSD and LHM. Electrophysiological studies have been consistent with both biochemical and behavioral findings with respect to the much greater effect of LHM on DA receptors. In fact, the effects of LSD on DA-containing neurons are both weak and heterogeneous, again indicating a need for more detailed analyses of specific DA projection systems. The greater potency of LHM than LSD on 5-HT containing dorsal raphe neurons has lessened the attractiveness of the once popular theory that hallucinogenic efficacy is related to diminution of impulse flow in 5-HT systems but has also spawned greater interest in the possible role of postsynaptic 5-HT receptors in hallucinogenic drug action. Thus far, the most interesting finding is the ability of LSD and other hallucinogens, but not LHM, to potentiate an excitomodulatory effect of 5-HT in the facial motor nucleus. If such a phenomenon occurs more generally in the CNS, the importance of this finding will be greatly enhanced. Preliminary data is presented which suggests that LSD may also induce such an effect in a limbic forebrain structure, the nucleus accumbens.(ABSTRACT TRUNCATED AT 400 WORDS)
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Arvidsson LE, Hacksell U, Glennon RA. Recent advances in central 5-hydroxytryptamine receptor agonists and antagonists. PROGRESS IN DRUG RESEARCH. FORTSCHRITTE DER ARZNEIMITTELFORSCHUNG. PROGRES DES RECHERCHES PHARMACEUTIQUES 1986; 30:365-471. [PMID: 3544048 DOI: 10.1007/978-3-0348-9311-4_11] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Barragan LA, Delhaye-Bouchaud N, Laget P. Drug-induced activation of the inferior olivary nucleus in young rabbits. Differential effects of harmaline and quipazine. Neuropharmacology 1985; 24:645-54. [PMID: 3160966 DOI: 10.1016/0028-3908(85)90107-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Ontogenic evolution of behavioural and electrophysiological responses to the serotonergic agents, quipazine and harmaline, was studied in the maturing rabbit in normal and pretreated conditions. As regards behavioural effects, tremor induced by quipazine was present from the first postnatal day and was antagonized by methysergide, but not by p-chlorophenylalanine (PCPA) or pretreatment with 5,7-dihydroxytryptamine (5,7-DHT). In contrast, tremor induced by harmaline could not be elicited before the second postnatal week and was partially antagonized by methysergide and 5,7-DHT, but not by PCPA. Electrophysiological studies of cell activity in the inferior olivary nucleus revealed a similar dependency on age since rhythmic activation of the inferior olivary nucleus could be registered from the first postnatal day with quipazine and only from the 8th postnatal day with harmaline; drug interactions with methysergide, PCPA and 5,7-DHT were the same as for the behavioural observations. It is suggested that quipazine directly activates serotonin receptors which are already present at birth, whereas harmaline requires the presence of serotonergic fibres for such activation.
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Friedman RL, Sanders-Bush E, Barrett RL. Clozapine blocks disruptive and discriminative stimulus effects of quipazine. Eur J Pharmacol 1984; 106:191-3. [PMID: 6529966 DOI: 10.1016/0014-2999(84)90695-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Clozapine was tested in two serotonin-dependent behavioral measures. One group of rats was trained to discriminate the serotonin agonist, quipazine, from saline in a two-lever operant choice task. Pretreatment with clozapine completely blocked the discrimination of quipazine. Another group of rats was trained to bar press for milk on a variable interval schedule of reinforcement. Quipazine decreased the response rate in these animals and pretreatment with clozapine completely reversed this effect. Thus, clozapine acted as a serotonin antagonist in both measures of serotonin function.
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19
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Abstract
The discriminative stimulus properties of the clinically important ergot derivative lisuride hydrogen maleate were studied by training 2 groups of rats to discriminate 0.04 mg/kg lisuride from saline and 0.16 mg/kg apomorphine from saline. Dose-response and substitution tests between these groups showed that lisuride and apomorphine are discriminated similarly by both groups and that lisuride is 5 to 9 times more potent. The dopaminergic agonists d-amphetamine, quipazine, bromocriptine, cocaine and cathinone did not substitute for lisuride. In antagonism studies, only the dopamine receptor blocker haloperidol attenuated the lisuride cue; the serotonin receptor blockers pirenperone and BC-105 were ineffective. These data indicate that the primary central action mediating the discriminative stimulus effects of lisuride was direct activation of dopamine receptors.
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Minnema DJ, Hendry JS, Rosecrans JA. Discriminative stimulus properties of pizotifen maleate (BC105): a putative serotonin antagonist. Psychopharmacology (Berl) 1984; 83:200-4. [PMID: 6431474 DOI: 10.1007/bf00429735] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Rats were trained to discriminate the putative serotonin (5-HT) antagonist, pizotifen maleate (BC105), from saline using a two-lever drug discrimination paradigm. Pizotifen maleate (6 mg/kg, 14.6 mumol/kg, IP) or saline was administered 55 min prior to the operant training session. The pizotifen discriminative stimulus (DS) had a rapid onset (less than 7 min) and was of long duration. The pizotifen DS was dose dependent. The pizotifen DS did not generalize to the putative 5-HT antagonists, methiothepin, xylamidine, and cinanserin. Partial generalization was observed to methysergide and metergoline, and complete generalization to cyrproheptadine and the phenothiazine antihistamine, promethazine. The pizotifen DS failed to generalize to the antipsychotic chlorpromazine, the ethanolamine antihistamine diphenhydramine, the CNS stimulant, d-amphetamine, and the putative 5-HT agonists, LSD and quipazine. LSD and quipazine failed to antagonize the pizotifen DS. The results of this study suggest that different DS properties are associated with the different putative 5-HT antagonists and that pizotifen and cyproheptadine, in addition to their reported 5-HT antagonist properties, share a common property that is also associated with promethazine, probably involving antihistaminergic activity.
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Stolerman IP, Pratt JA, Garcha HS, Giardini V, Kumar R. Nicotine cue in rats analysed with drugs acting on cholinergic and 5-hydroxytryptamine mechanisms. Neuropharmacology 1983; 22:1029-37. [PMID: 6138726 DOI: 10.1016/0028-3908(83)90021-7] [Citation(s) in RCA: 70] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The nicotine discriminative stimulus (cue) has been used to characterize further the underlying receptor mechanisms. Rats were trained to discriminate the effects of nicotine in a standard, two-bar operant conditioning procedure with food reinforcement. Mecamylamine blocked both the discriminative effect of nicotine and the reducing effect on the response-rate. The block of the discriminative effect could not be overcome by increasing the dose of nicotine, whereas the block of the reducing effect on the response-rate could be reversed. Mecamylamine was effective when administered by either the subcutaneous or the intraventricular route, but hexamethonium was inactive by both routes. Mecamylamine, but not hexamethonium, blocked the discriminative effect of the nicotinic cholinergic agonist, cytisine. Methergoline did not block the discriminative effects of nicotine, even in doses considerably larger than those which blocked the discriminative effects of the 5-HT agonist, quipazine. Mecamylamine did not block the effects of quipazine. The results are consistent with the view that the nicotinic cue is mediated primarily through cholinergic receptors, and that 5-HT mechanisms are not involved. The block of the quipazine cue supports the view that the discriminative effects of this drug are mediated through 5-HT receptors.
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22
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Colpaert FC, Janssen PA. A characterization of LSD-antagonist effects of pirenperone in the rat. Neuropharmacology 1983; 22:1001-5. [PMID: 6621823 DOI: 10.1016/0028-3908(83)90216-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Rats were trained to discriminate between intraperitoneal injections of 0.16 mg/kg of d-lysergic acid diethylamide (d-LSD) and injections of saline in the two-bar (FR 10) food-reinforced drug discrimination procedure. The gradient for responses to LSD was established following pretreatment with saline or one of five doses of pirenperone. It was found that pretreatment with pirenperone caused a parallel shift to the right of the dose-effect curve of LSD. The magnitude of this shift was related to the dose of pirenperone, 0.006 mg/kg of the drug causing a 2-fold shift. A direct linear plot revealed that the curve fitting the data points passed through the origin, but that it was curvilinear rather than linear. The data did not, therefore, accommodate the requirements for reversible, competitive interaction. This finding is discussed in terms of the mixed agonist/antagonist activity of LSD that may occur at binding sites for 5-HT1 and 5-HT2 in the rat brain.
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Glennon RA, Rosecrans JA, Young R. Drug-induced discrimination: a description of the paradigm and a review of its specific application to the study of hallucinogenic agents. Med Res Rev 1983; 3:289-340. [PMID: 6350763 DOI: 10.1002/med.2610030305] [Citation(s) in RCA: 70] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Friedman R, Barrett RJ, Sanders-Bush E. Additional evidence that L-5-hydroxytryptophan discrimination models a unique serotonin receptor. Psychopharmacology (Berl) 1983; 80:209-13. [PMID: 6137018 DOI: 10.1007/bf00436154] [Citation(s) in RCA: 8] [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: 01/18/2023]
Abstract
The purpose of the present studies was to investigate further the role of central serotonin (5-HT) in mediating the L-5-hydroxytryptophan (L-5-HTP) discriminative cue. Rats were trained to discriminate the stimulus properties of 35 mg/kg L-5-HTP combined with RO 4-4602, a peripheral decarboxylase inhibitor. Considering that several 5-HT antagonists were unable to block the L-5-HTP discriminative cue in our earlier studies, we extended these studies to include the two other presumed 5-HT antagonists mianserin and BC-105 (pizotyline). Only BC-105 completely blocked the training dose of L-5-HTP. Furthermore, the blockade of the L-5-HTP cue was both graded and surmountable by increasing the dose of L-5-HTP, suggesting a competitive antagonism. In neurochemical studies, the regional brain levels of 5-HT, norepinephrine and dopamine were determined after the injection of the training dose of L-5-HTP. Marked changes in the levels of 5-HT were found, while the levels of the catecholamines were changed only slightly or not at all. Furthermore, dose-response studies of L-5-HTP demonstrated an orderly dose-related increase in the levels of 5-HT in brain and in the percent responding on the L-5-HTP lever, while no such relationship was found for brain catecholamines. These results agree with previous pharmacological studies and suggest that the L-5-HTP discrimination is mediated by a central 5-HT receptor that has pharmacological properties distinct from those receptors identified in previous behavioral models of 5-HT receptor stimulation.
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Pratt JA, Stolerman IP, Garcha HS, Giardini V, Feyerabend C. Discriminative stimulus properties of nicotine: further evidence for mediation at a cholinergic receptor. Psychopharmacology (Berl) 1983; 81:54-60. [PMID: 6415731 DOI: 10.1007/bf00439274] [Citation(s) in RCA: 103] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Rats were trained to discriminate nicotine (0.4 mg/kg SC) from saline in a standard two-bar operant conditioning procedure with food reinforcement. The response to nicotine was dose-related and at the ED50 of 0.14 mg/kg, plasma nicotine concentrations were similar to those reported previously for cigarette smokers who inhale. The nicotine analogues anabasine and cytisine increased nicotine-appropriate responding in a dose-related manner. Animals predominantly responded on the saline-associated lever when administered drugs from a range of pharmacological classes, even at doses that were sufficiently large to reduce the overall numbers of responses. The results confirm that the nicotine discriminative stimulus is highly specific. Previous work has shown anabasine and cytisine to be active at nicotinic-cholinergic binding sites in rat brain. The finding that there is some correlation between the behavioural effects of these compounds and their actions at the nicotine binding site may indicate that the nicotine cue is mediated through a cholinergic receptor.
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Abstract
Rats were trained to discriminate between the stimulus properties of intraperitoneal 0.16 mg/kg apomorphine and saline in a two-lever, food-motivated operant task. Administration of 1.0 mg/kg quipazine, a putative serotonin agonist, produced apomorphine-appropriate responding with a maximal effect occurring at 45 min post-injection. Pretreatment with either 2.0 mg/kg methysergide or 0.4 mg/kg haloperidol reduced quipazine-induced responding upon the apomorphine-appropriate lever to levels observed with methysergide or haloperidol administered alone. These results evidence a dopaminergic action for quipazine and suggest that central serotonergic and dopaminergic pathways may interact cooperatively to control behavior.
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Abstract
Quipazine produced a dose-dependent decrease in the discharge rate of serotonin-containing neurons in the dorsal raphe nucleus of freely-moving cats. This ranged from a 10% decrease at 0.5 mg/kg, (i.p.), to a virtually complete depression of activity at 5.0 mg/kg. The effects of quipazine on raphe units occurred with a short latency (5--10 min) and its duration of action was dose-dependent and lasted from 1 to 6 hr. The degree of depression of raphe unit activity was directly related to the frequency of occurrence of a number of behaviors such as limb flicking and abortive grooming. There was a close temporal correlation between the depression of raphe unit activity and the occurrence of these behaviors. These data reveal that quipazine produces behavioral and raphe unit changes similar to those observed after administration of hallucinogens with an indole nucleus.
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Rowland N, Antelman SM, Kocan D. Differences among 'serotonergic' anorectics in a cross-tolerance paradigm: do they all act on serotonin systems? Eur J Pharmacol 1982; 81:57-66. [PMID: 7117371 DOI: 10.1016/0014-2999(82)90601-x] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Rats on a 4 hr/day feeding schedule showed anorexia after i.p. injections of several 'serotonergic' agents. Tolerance developed within a few days of daily administration of all drugs except fluoxetine. The tolerant animals were then given a cross-tolerance test with a different agent, either the next day or after a drug free washout period. Rats which were tolerant to quipazine or MK 212 showed no cross-tolerance to fenfluramine or norfenfluramine. In contrast, rats which were tolerant to fenfluramine showed good cross-tolerance to quipazine or MK 212. However, after a washout period between the end of the chronic fenfluramine regimen and the cross-tolerance test, quipazine regained its full anorectic potency. The development of tolerance to fenfluramine was dependent upon the number of injections, not on their spacing. Fenfluramine-tolerant animals showed a partial decay of tolerance after a 3 day washout, but still retained some tolerance after 12 days. These findings imply that the mechanisms underlying the development of tolerance may differ from those which mediate its maintenance. Our data further suggest that not all of the agents act on the same neural system(s), and raise the possibility that non-serotonergic and/or non-cerebral systems may be involved in the mode of action of these agents.
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Leskawa KC, Rosenberg A. Displacement of Ca2+ bound to synaptosomal membrane sialoglycoconjugates by serotonin and serotonergic drugs and the effect on endogenous sialidase (neuraminidase) activity. Biochem Pharmacol 1982; 31:1787-90. [PMID: 6179520 DOI: 10.1016/0006-2952(82)90687-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Abstract
Administration of quipazine to cats elicits a number of behaviors, such as limb flicking abortive grooming, investigatory behavior and hallucinatory-like behavior, which we have previously proposed as an animal behavioral model for studying the actions of LSD and related hallucinogens. While recent studies have indicated that these model behaviors may not be totally specific for hallucinogenic drugs, the model can still be useful for studying drug action. Quipazine (0.5-5.0 mg/kg i.p.) produced significant increases in limb flicking, abortive grooming, investigatory behavior, hallucinatory-like behavior grooming, head and body shakes, staring and yawning. These behavioral changes persisted for 1-6 h, depending on the dose of quipazine employed. Administration of quipazine (5.0 mg/kg per day) for 5 consecutive days produced no significant tolerance effect on any of these model behaviors. These quipazine induced behavioral changes were potentiated by pretreatment with apomorphine, and partially blocked by pretreatment with haloperidol. Quipazine-induced behavioral changes were potentiated by prior serotonin depletion with p-chlorophenylalanine, and completely blocked by pretreatment with a monoamine oxidase inhibitor or the serotonin precursor, L-5-hydroxytryptophan. These quipazine-induced behavioral changes were also blocked by pretreatment with the serotonin receptor blockers, cinnanserin, methysergide or cyproheptadine. The mechanism of action of quipazine, as well as the neuropharmacology of the limb flick model, is discussed in the content of these studies with serotonergic and dopaminergic drugs.
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Abstract
The effects of single oral administrations of tricyclic antidepressants (imipramine and desipramine), an atypical antidepressant (nomifensine), known anorexic agents, haloperidol, and diazepam on food intake were compared in Sprague-Dawley rats over a 4-day test period. The tricyclic antidepressants produced decreases in food intake during the total 4-day test period following their administration. In contrast, the anorexic agents (d-amphetamine, cocaine, mazindol, fenfluramine and quipazine), and nomifensine, and haloperidol produced decreases in food intake only on their administration. Diazepam produced an increase in food intake only on the day of its decrease food intake, this model appears to show some specificity for tricyclic antidepressants.
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Hyttel J. Citalopram--pharmacological profile of a specific serotonin uptake inhibitor with antidepressant activity. Prog Neuropsychopharmacol Biol Psychiatry 1982; 6:277-95. [PMID: 6128769 DOI: 10.1016/s0278-5846(82)80179-6] [Citation(s) in RCA: 461] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
1. Citalopram (Lu 10-171), a new bicyclic phthalane derivative, is an extremely potent inhibitor of neuronal serotonin (5-HT) uptake but has no effect on the uptake of noradrenaline (NA) and dopamine (DA). 2. Citalopram has no antagonistic activity towards DA, NA, 5-HT, histamine, gamma aminobutyric acid (GABA), acetylcholine, and morphine receptors. In this way it clearly deviates from many old and new antidepressant drugs which have antagonistic effects towards some of these transmitters. 3. In contrast to many tricyclic antidepressants citalopram is devoid of cardiotoxic effects, even when animals are exposed to concentrations far above the therapeutic level. 4. In man citalopram is metabolized to compounds which are also potent 5-HT-uptake inhibitors without effect of NA uptake and which are found in lower concentrations than citalopram itself. 5. In account of its extreme specificity as a 5-HT-uptake inhibitor citalopram should be considered as an experimental tool of the utmost importance. In preliminary clinical experiments citalopram has shown a clear antidepressant effect. This property together with the absence of troublesome anticholinergic adverse effects and cardiotoxic effects also make citalopram a most promising antidepressant drug.
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Barrett RJ, Blackshear MA, Sanders-Bush E. Discriminative stimulus properties of L-5-hydroxytryptophan: behavioral evidence for multiple serotonin receptors. Psychopharmacology (Berl) 1982; 76:29-35. [PMID: 6805004 DOI: 10.1007/bf00430750] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Rats were trained to discriminate the stimulus properties of L-5-hydroxytryptophan (L-5-HTP) (30 mg/kg SC), the immediate precursor of serotonin (5-HT). The peripheral decarboxylase inhibitor R04-4602, administered prior to L-5-HTP, greatly attenuated the disruptive effects observed on responding when L-5-HTP alone was injected. Following acquisition, the discrimination was dose-dependent and generalized to fenfluramine, a 5-HT-releasing drug, but not to amphetamine, a catecholamine-releasing agent. Further evidence for the involvement of 5-HT receptor stimulation in mediating the discrimination was that pretreatment with fluoxetine, a highly specific 5-HT uptake inhibitor, markedly potentiated the cue. Nevertheless, the classical 5-HT antagonists methysergide, cyproheptadine, metergoline, and methiothepin did not block the L-5-HTP-related discriminative stimulus. This finding suggested that the cue properties of L-5-HTP might be mediated by a population of 5-HT receptors previously identified electrophysiologically in limbic structures. As in the present experiment, the putative 5-HT antagonists did not block the synaptic effects of 5-HT in these structures.
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White FJ, Holohean AM, Appel JB. Lack of specificity of an animal behavior model for hallucinogenic drug action. Pharmacol Biochem Behav 1981; 14:339-43. [PMID: 7232460 DOI: 10.1016/0091-3057(81)90400-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
It has been proposed recently that the occurrence of drug-induced limb-flicking (LF) and abortive grooming (AG) in cats can serve as a viable animal behavior model for the actions of hallucinogens in humans. If this is the case, such behaviors should occur reliably following the administration of drugs that produce hallucinations in humans and should not occur after administration of other, non-hallucinogenic drugs--a hypothesis that was examined in the present experiment. The frequency of LF and AG were observed in 12 cats which were given a wide range of doses of the potent hallucinogen, d-LSD (0.01-0.16 mg/kg), as well as several other compounds. The results showed that three non-hallucinogenic agents which are related to LSD in various ways, the ergot derivative lisuride, the serotonin agonist, quipazine, and the dopamine agonist, apomorphine, significantly increased LF frequency. Lisuride and quipazine also caused AG. Cocaine did not elicit either behavior. Thus, it was concluded that the proposed model cannot be regarded as specific to hallucinogenic drugs. In addition, the frequency of these behaviors, as well as their reliability and robustness, were shown to be party dependent on the environment in which observation occurs.
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White FJ, Appel JB. A neuropharmacological analysis of the discriminative stimulus properties of fenfluramine. Psychopharmacology (Berl) 1981; 73:110-5. [PMID: 6785800 DOI: 10.1007/bf00429199] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Rats were trained to discriminate fenfluramine (1.0 mg/kg) from saline in a two-lever drug discrimination task. The dose-response curve for this discrimination was orderly with an ED50 of about one-half of the training dose (0.52 mg/kg). In substitution tests, indirect (p-chloroamphetamine) and direct (quipazine, MK-212, lisuride) serotonin (5-HT) agonists substituted for fenfluramine. Since none of these compounds have been reported to be hallucinogenic and the potent hallucinogen LSD did not substitute completely, it was suggested that the discriminative stimulus properties of fenfluramine are not related to its ability to produce hallucinations in humans. The fenfluramine cue, like the quipazine cue, was antagonized by the 5-HT antagonists cyproheptadine and methiothepin. Unlike quipazine, fenfluramine was also partially antagonized by the 5-HT uptake inhibitor, fluoxetine, and the 5-HT synthesis inhibitor, p-chlorophenylalanine. Thus, the fenfluramine cue differs from that of quipazine in that it is mediated via indirect actions on 5-HT receptors. Since the indirect dopamine (DA) agonist d-amphetamine failed to substitute and the DA antagonist haloperidol failed to block the fenfluramine cue, a mediating role for DA was not indicated. Another indirect DA agonist, cocaine, substituted partially for fenfluramine, a result which paralleled that seen with fluoxetine. Both of these partial substitutions were reduced by cyproheptadine; therefore, it was concluded that these effects may be due to the common ability of cocaine, fluoxetine, and fenfluramine to inhibit 5-HT uptake.
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Broekkamp CL, Garrigou D, LLoyd KG. Serotonin-mimetic and antidepressant drugs on passive avoidance learning by olfactory bulbectomised rats. Pharmacol Biochem Behav 1980; 13:643-6. [PMID: 6969405 DOI: 10.1016/0091-3057(80)90006-4] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Olfactory bulbectomised rats were treated with drugs and their rate of acquisition of a passive avoidance task was measured. The acquisition-rate, which is disturbed by the bilateral ablations, was completely restored by acute administration of fenfluramine or fluoxetine. Partial restoration was found with quipazine. Clonidine was without effect. Repeated treatments with imipramine and mianserine improved passive avoidance of bulbectomised rats. Metergoline blocked these effects of imipramine and mianserin. These results indicate a serotonergic mechanism in the effect of antidepressants on olfactory bulbectomised rats.
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White FJ, Simmons MA, West KB, Holohean AM, Appel JB. The effect of serotonin depletion on the discriminability of LSD. Pharmacol Biochem Behav 1980; 13:569-74. [PMID: 6449014 DOI: 10.1016/0091-3057(80)90282-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Nine groups of rats were trained to discriminate LSD (0.12 mg/kg) from saline in a two-lever, water-reinforced, drug discrimination procedure. After stable discriminative performance was obtained (>95% correct), groups were administered one of several treatments which lower the concentration of serotonin (5-HT) in brain: (1) 12.5, 25, 50, 100 or 200 microgram of 5,7-dihydroxytryptamine (5,7-DHT) intraventricularly (IVT); (2) 3 X 100 mg/kg of p-chlorophenylalanine (PCPA) intraperitoneally (IP); or (3) 20 mg/kg of p-chloroamphetamine (PCA) IP. Control rats received either IVT injections of 5,7-DHT vehicle or IP injections of PCA or PCPA vehicles. Beginning 12 days after treatment, lever preference following various doses of LSD was determined. The results indicated that only the 200 microgram dose of 5,7-DHT and PCPA caused a significant potentiation of LSD-lever responding at the 0.03 mg/kg dose of LSD while all treatments except 12.5 and 25 microgram of 5,7-DHT resulted in significant depletion of 5-HT. Moreover, amount of 5-HT and percent LSD responding following 0.03 mg/kg LSD were not significantly correlated. It was concluded that 5-HT depletion, per se, cannot account for supersensitivity to the behavioral effects of LSD.
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Abstract
Pigeons (N=4) were trained to discriminate between the effects induced by intramuscular (IM) injections of d-LSD and saline using a discrete-trial discrimination paradigm (choice between left and right hand key) in a conventional operant box. The solutions were administered IM 15 min prior to the sessions. A FR 15 schedule was in operation to produce food. Which of the two keys was correct on a given training session depended upon whether LSD or saline had been given. Three of the birds were trained and maintained with a dose of 40 microgram/kg of LSD and the fourth pigeon finally was maintained on 50 microgram/kg of LSD. The dose resulting in 50% LSD appropriate responding (ED50) was 18 microgram/kg and the median time-interval for the decay of the LSD stimulus (40 microgram/kg) was 84 min. Tests with psilocybin (ED50=0.55 mg/kg) and N,N-dimethyltryptamine (ED50=5.7 mg/kg) resulted in responding appropriate for the LSD training condition. Mescaline injections above 10 mg/kg severely suppressed responding. The few responses emitted after tests with 15 and 20 mg/kg of mescaline were directed to the LSD associated key. Tests with BOL (0.1 to 3 mg/kg) as well as three other psychotropic drugs (delta 9-tetrahydrocannabinol, morphine and, pentobarbital) did not result in responding above 50%) LSD appropriate responses. As a possible antidote, methergoline, a pubetative antagonist of post-synaptic serotonin receptor sites, was administered 75 min prior to testing the cueing properties of LSD. No definitive role for a blocking effect of the LSD-cue is provided by the present data.
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Winter JC. Effects of the phenethylamine derivatives, BL-3912, fenfluramine, and Sch-12679, in rats trained with LSD as a discriminative stimulus. Psychopharmacology (Berl) 1980; 68:159-62. [PMID: 6776559 DOI: 10.1007/bf00432134] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Six rats were trained to discriminate the effects of LSD (100 micrograms/kg) and saline in a two-lever choice task. They were then tested with each of three phenethylamine derivatives, BL-3912 (2,5-dimethoxy-4-methyl-alpha-ethyl-phenethylamine), fenfluramine (N-ethyl-alpha-methyl-m-(trifluoro-methyl)phenethylamine), and Sch-12679 (N-methyl-1-phenyl-7,8-dimethoxy-2,3,4,5-tetra-hydro-3-benzazepine maleate). Fenfluramine and Sch-12679 yielded intermediate results, i.e., responding was not fully appropriate for either training condition while BL-3912 substituted completely for LSD. The LSD-like effects of each of the drugs were antagonized by pretreatment with BC-105, a serotonergic antagonist known to block the stimulus effects of indole and phenethylamine hallucinogens. The present data together with consideration of the known clinical effects of BL-3912, fenfluramine, and Sch-12679 are consistent with the following conclusions: (1) a variety of drugs may substitute in whole or in part for LSD in LSD-trained rats, and (2) even complete substitution of a drug for LSD in the rat is not necessarily associated with the production by that drug of hallucinations in man.
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Colpaert FC, Niemegeers CJ, Janssen PA. In vivo evidence of partial agonist activity exerted by purported 5-hydroxytryptamine antagonists. Eur J Pharmacol 1979; 58:505-9. [PMID: 510385 DOI: 10.1016/0014-2999(79)90326-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Using a food-reinforced two-lever operant method, rats (n = 9) were trained to discriminate 0.16 mg/kg LSD from saline. Tests for stimulus generalization in rats so trained indicated that the purported 5-HT antagonists cyproheptadine (1.25 and 10 mg/kg), methysergide (0.16 to 10 mg/kg) and mianserin (2.5 to 40 mg/kg) produced partial generalization with LSD. The hallucinogens mescaline (5 to 40 mg/kg) and quipazine (1.25 to 5 mg/kg) were also generalized with LSD. The data suggest that cyproheptadine, methysergide and mianserin may produce partial agonist effects in addition to their antagonist action at central 5-HT receptor sites.
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