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Abstract
This is a retrospective examination of former users of alpha-methyltryptamine (AMT). A scale of questions was given to subjects who were familiar with the effects of AMT and the outcome was analyzed. Most subjects agreed that AMT had strong hallucinogenic qualities. The most common unwanted effects included anxiety, nausea and moderately severe dysphoria. Several subjects reported significant depression associated with use of AMT. Use of alpha-methyltryptamine could be dangerous in individuals prone to depression.
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Green AR. Gaddum and LSD: the birth and growth of experimental and clinical neuropharmacology research on 5-HT in the UK. Br J Pharmacol 2008; 154:1583-99. [PMID: 18516072 PMCID: PMC2518468 DOI: 10.1038/bjp.2008.207] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2008] [Revised: 04/25/2008] [Accepted: 04/30/2008] [Indexed: 11/08/2022] Open
Abstract
The vasoconstrictor substance named serotonin was identified as 5-hydroxytryptamine (5-HT) by Maurice Rapport in 1949. In 1951, Rapport gave Gaddum samples of 5-HT substance allowing him to develop a bioassay to both detect and measure the amine. Gaddum and colleagues rapidly identified 5-HT in brain and showed that lysergic acid diethylamide (LSD) antagonized its action in peripheral tissues. Gaddum accordingly postulated that 5-HT might have a role in mood regulation. This review examines the role of UK scientists in the first 20 years following these major discoveries, discussing their role in developing assays for 5-HT in the CNS, identifying the enzymes involved in the synthesis and metabolism of 5-HT and investigating the effect of drugs on brain 5-HT. It reviews studies on the effects of LSD in humans, including Gaddum's self-administration experiments. It outlines investigations on the role of 5-HT in psychiatric disorders, including studies on the effect of antidepressant drugs on the 5-HT concentration in rodent and human brain, and the attempts to examine 5-HT biochemistry in the brains of patients with depressive illness. It is clear that a rather small group of both preclinical scientists and psychiatrists in the UK made major advances in our understanding of the role of 5-HT in the brain, paving the way for much of the knowledge now taken for granted when discussing ways that 5-HT might be involved in the control of mood and the idea that therapeutic drugs used to alleviate psychiatric illness might alter the function of cerebral 5-HT.
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Affiliation(s)
- A R Green
- Institute of Neuroscience, School of Biomedical Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, UK.
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Abstract
Over the past 40 years, much has been learned about the role of serotonin in spinal cord reflex modulation and locomotor pattern generation. This review presents an historical overview and current perspective of this literature. The primary focus is on the mammalian nervous system. However, where relevant, major insights provided by lower vertebrate models are presented. Recent studies suggest that serotonin-sensitive locomotor network components are distributed throughout the spinal cord and the supralumbar regions are of particular importance. In addition, different serotonin receptor subtypes appear to have different rostrocaudal distributions within the locomotor network. It is speculated that serotonin may influence pattern generation at the cellular level through modulation of plateau properties, an interplay with N-methyl-D-aspartate receptor actions, and afterhyperpolarization regulation. This review also summarizes the origin and maturation of bulbospinal serotonergic projections, serotonin receptor distribution in the spinal cord, the complex actions of serotonin on segmental neurons and reflex pathways, the potential role of serotonergic systems in promoting spinal cord maturation, and evidence suggesting serotonin may influence functional recovery after spinal cord injury.
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Affiliation(s)
- B J Schmidt
- Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada.
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Abstract
In rats, three alpha-alkylated tryptamine derivatives (alpha-methyl, alpha-ethyl, and alphaalpha-dimethyltryptamine) caused alterations of 5-hydroxytryptamine metabolism typical of monoamine-oxidase inhibitors with short duration of action, viz., an increase of endogenous 5-hydroxytryptamine in brain, enhancement of the increase of 5-hydroxytryptamine in brain and heart after 5-hydroxytryptophan administration, an inhibition of the decrease in 5-hydroxytryptamine in brain induced by a benzoquinolizine derivative and of the increase induced by iproniazid. The increase after iproniazid was antagonized to the same extent by all the tryptamine derivatives and by harmaline, whereas dexamphetamine showed less effect. In the other experiments with brain, the tryptamine derivatives were less potent than harmaline, but somewhat more active than dexamphetamine. alpha-Methyltryptamine and alpha-ethyltryptamine were relatively more effective in the heart than in the brain. Among the tryptamine derivatives alphaalpha-dimethyltryptamine had the weakest activity in brain and in heart.
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Abstract
Indoles related to 5-hydroxytryptamine, lysergic acid derivatives, phenethylamine derivatives and some other compounds have been applied electrophoretically to the neurones of the lateral geniculate nucleus of the cat anaesthetized with pentobarbitone sodium. Many of these compounds, particularly 4-, 5- and 7-hydroxytryptamine and ergometrine, depress the orthodromic excitation of the neurones by volleys in optic nerve fibres, but do not affect antidromic excitation by volleys in the optic radiation or chemical excitation by L-glutamic acid. It is concluded that the active depressants either block the access of the excitatory transmitter to subsynaptic receptors or prevent the release of the transmitter from optic nerve terminals. The structure-activity relationships of the depressant substances are discussed.
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CORNE SJ, PICKERING RW, WARNER BT. A method for assessing the effects of drugs on the central actions of 5-hydroxytryptamine. Br J Pharmacol Chemother 1998; 20:106-20. [PMID: 14023050 PMCID: PMC1703746 DOI: 10.1111/j.1476-5381.1963.tb01302.x] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Injection of 5-hydroxytryptophan into mice produces a characteristic head-twitch. For a given period of observation this response may be assessed quantitatively either by observing the proportion of mice showing at least one head-twitch (a quantal response) or by counting the number of head-twitches for each mouse (a graded response). A method, based on the quantal response, of investigating the effect of centrally acting compounds on the head-twitch response is described. Evidence is presented that the head-twitches are due to a central action of 5-hydroxytryptamine formed by decarboxylation of 5-hydroxytryptophan. Head-twitches are potentiated by monoamine oxidase inhibitors and by phenytoin. Antagonists tested include an inhibitor of decarboxylase, antagonists of 5-hydroxytryptamine, some antihistamines, major tranquillizers and analgesic and sympathomimetic drugs. Drugs which neither potentiate nor inhibit the response include barbiturates and minor tranquillizers. The method may be valuable in the preliminary examination of compounds likely to have a central action.
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BRADLEY PB, MARLEY E. EFFECT OF TRYPTAMINE AND TRYPTAMINE HOMOLOGUES ON CEREBRAL ELECTRICAL ACTIVITY AND BEHAVIOUR IN THE CAT. Br J Pharmacol Chemother 1996; 24:659-74. [PMID: 14340920 PMCID: PMC1704018 DOI: 10.1111/j.1476-5381.1965.tb01622.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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HALLIWELL G, QUINTON RM, WILLIAMS FE. A COMPARISON OF IMIPRAMINE, CHLORPROMAZINE AND RELATED DRUGS IN VARIOUS TESTS INVOLVING AUTONOMIC FUNCTIONS AND ANTAGONISM OF RESERPINE. Br J Pharmacol Chemother 1996; 23:330-50. [PMID: 14228134 PMCID: PMC1704096 DOI: 10.1111/j.1476-5381.1964.tb01590.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Seven structurally-related compounds consisting of three antidepressant drugs (imipramine, desmethylimipramine and amitriptyline), three tranquillizing agents (promazine, chlorpromazine and chlorprothixene) and a hybrid, desmethylpromazine, have been examined in a series of tests involving autonomic functions and antagonism of reserpine. Activities of the compounds in antagonizing reserpine-induced ptosis in rabbits and prolongation of alcohol hypnosis in mice give good correlation with their clinical actions, whilst their activities in augmenting excitation of rats by amphetamine and yohimbine toxicity in mice, and in reversing reserpine-induced bradycardia in rats offer further evidence for drug-induced sensitization to adrenergic or tryptaminic mechanisms, which is not however specific for antidepressant agents. No evidence has been obtained to indicate that a central parasympatholytic action is an important component of the antidepressant activity of imipramine and related drugs.
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Abstract
Mammalian lungs have been shown to store and to inactivate serotonin (5-HT) by an active process involving uptake and metabolism. 5-HT has direct action on lung including constrictor effects of pulmonary vascular and tracheobronchial smooth muscle, suggesting the presence of 5-HT receptors in lung. We have identified specific 5-HT binding of high affinity to the different lung portions and have shown that there was a different capacity for this binding. Two different 5-HT-binding capacities are present in a purified mitochondrial fraction. Saturation analysis of 5-[3H]HT binding to outer mitochondrial membranes demonstrates a single, temperature-sensitive, high-affinity and high-capacity binding (Kd = 8.3 +/- 1.2 nM, maximum binding capacity = 0.819 +/- 0.046 pmol/mg protein). The dissociation constant of inner mitochondrial membrane demonstrates a low-capacity site (Kd = 25.2 +/- 2.2 nM, maximum binding capacity = 0.453 +/- 0.037 pmol/mg protein). The purified microsomal fraction of lung exhibits a high-capacity binding site for 5-[3H]HT (Kd = 14.8 +/- 1.6 nM, maximum binding capacity = 0.760 +/- 0.03 pmol/mg protein). In addition to the lung being the major site for its inactivation, the presence of several specific 5-HT receptors may be related to some of the known 5-HT actions in lung and may suggest other unknown actions of this amine.
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Abstract
Tryptamine was applied directly into the spinal subarachnoid space of rats via permanently indwelling cannulas. Changes in pain-perception were measured by changes in the latency of the tail-flick in response to a radiant heat source of low intensity. While an intrathecal injection of serotonin has been previously shown to be analgesic, exogenous tryptamine produced dual effects on the pain-threshold, depending on the dose of tryptamine injected. Low doses of tryptamine (100 and 200 micrograms/rat) injected intrathecally onto the sacral area of the spinal cord appeared to be hyperalgesic by significantly decreasing the average tail-flick latency by 5 min after injection. Administration of the serotonin antagonist methysergide alone was without effect on the average tail-flick reaction time when injected either intrathecally or subcutaneously. However, pretreatment with either methysergide or cinanserin not only failed to inhibit tryptamine's potentiation of nociception, but actually enhanced the hyperalgesia produced by tryptamine. In contrast, a dose of 400 micrograms of tryptamine significantly increased the average tail-flick latency, suggesting an analgesic effect at this higher dose. This analgesic effect of 400 micrograms of tryptamine was completely inhibited by subcutaneously administered methysergide, while intrathecally injected methysergide produced even greater decreases in the tail-flick latencies after this high dose of tryptamine. These results suggest that tryptamine, although it differs from serotonin by only one hydroxyl group, may play a role in nociception which is opposite that played by serotonin.
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Glennon RA, Young R, Jacyno JM. Indolealkylamine and phenalkylamine hallucinogens. Effect of alpha-methyl and N-methyl substituents on behavioral activity. Biochem Pharmacol 1983; 32:1267-73. [PMID: 6573879 DOI: 10.1016/0006-2952(83)90281-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Animals (rats), trained to discriminate the hallucinogenic agent 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM) from saline in a two-lever operant procedure, were challenged with various doses of several indolealkylamine and phenalkylamine derivatives. In both series, the alpha-methyl analogs were found to be more active than either their N-methyl or alpha-demethyl counterparts. Furthermore, when the activities of the optical isomers of DOM were compared with the activities of S-(+) and R-(-)-alpha-methyltryptamine (alpha-MeT), it was found that the more potent isomer of alpha-MeT (i.e. S) possessed the opposite absolute configuration of the more potent isomer of DOM (i.e. R). With respect to the mechanism of action of these agents, these findings are not inconsistent with a common site hypothesis.
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Abstract
Tryptamine synthesized by decarboxylation of L-tryptophan occurs as an endogenous constituent of mammalian brain albeit at very low concentrations (low ng/g range). It is primarily metabolized by oxidative deamination by MAO and possesses an extremely rapid turnover and half-life. Subcellular localization appears to be in nerve terminals and it is releasable by electrical or potassium evoked depolarization. Neuropharmacological and electrophysiological data strongly suggest the existence of post-synaptic receptors for tryptamine independent of those for 5HT. There may exist a rostrally projecting neuronal tryptamine containing system arising from cell bodies in or close to the nucleus raphé medianus. The demonstration of specific receptors for tryptamine in the CNS strongly indicates a transmitter role, although a strong case can be made for a role as a modifier of central 5HT systems. The possibility also exists that 5HT and tryptamine may be mediators of functionally opposite neuronal pathways. Whatever the role of tryptamine in the CNS it is clear that it not simply present as an accident of metabolism or a "biological artefact." The indications are that it possesses important functions in central neurotransmission.
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Chapin RE, Breese GR, Mueller RA. Antagonism of ethanol-induced decrease in LH by para-chlorophenylalanine: lack of correlation with altered serotonergic mechanisms. Pharmacol Biochem Behav 1981; 14:293-8. [PMID: 6453351 DOI: 10.1016/0091-3057(81)90393-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Acute administration of ethanol lowers plasma levels of luteinizing hormone (LH) in several species. Since ethanol may interact with central serotonergic (5HT) neurons, and since 5HT systems have been found to play a role in modulating LH release, we examined the possible role of central serotonergic neurons in the ethanol-induced depression of LH. Acute PCPA (400 mg/kg, 20 hr before 2.0 g/kg ethanol) was effective in preventing the ethanol-induced depression of LH, suggesting that ethanol activates 5HT systems to lower LH. In support of this, the central 5HT agonist 5-methoxy-N, N-dimethyltryptamine (5MDMT) depressed LH in a dose-dependent manner. However, while the effects of a sub-maximal dose of 5MDMT were blocked by prior administration of methysergide, this 5HT receptor antagonist was unable to prevent the post-ethanol fall in LH. Additionally, because other doses of PCPA (250 mg/kg 20 hr prior to ethanol, and 100 mg/kg P.O. x 3 days before ethanol) produced similar reductions in hypothalamic 5HT but did not block the ethanol effect, and because electrolytic lesions of the median raphe nucleus were also ineffective in preventing the post-ethanol depression of LH, we conclude that activation of serotonergic systems does not play a major role in the ethanol induced depression of LH.
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Abstract
A standard dose of 10 mg/kg (48 mu mole/kg) of (+/-)-alpha-methyltryptamine (AMT) induced a significant and long lasting increase in spontaneous activity in mice. Pretreatment of mice with either pimozide or alpha-methyl-para-tyrosine methyl ester HCl (AMPT) prevented the activity increase induced by AMT. In similar trials, methysergide or para-chlorophenylalanine (PCPA) were also found to antagonize the development of hyperactivity following a standard dose of AMT. The results suggest that both endogenous dopamine and serotonin many participate in the hyperactivity induced by AMT.
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Colpaert FC, Niemegeers CJ, Kuyps JJ, Janssen PA. Narcotic cue and narcotic state: differential involvement of brain 5-hydroxytryptamine. Neuropharmacology 1977; 16:65-70. [PMID: 189248 DOI: 10.1016/0028-3908(77)90049-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Abstract
Alpha-methyltryptamine, a drug which stimulates serotonergic receptors in the central nervous system, inhibited the induction of sexual receptivity in spayed female rats by estradiol benzoate and progesterone. The drug had no effect on the sexual receptivity induced by estradiol benzoate alone. These data are consistent with the hypothesis that progesterone facilitates lordosis in estrogen-primed rats by inhibiting a serotonergic system in the brain. The data also suggest that estradiol and progesterone act on separate neurochemical systems to induce estrous behavior in rats.
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Haigler HJ, Aghajanian GK. Peripheral serotonin antagonists: failure to antagonize serotonin in brain areas receiving a prominent serotonergic input. J Neural Transm (Vienna) 1974; 35:157-273. [PMID: 4373531 DOI: 10.1007/bf02205223] [Citation(s) in RCA: 252] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Vasko MR, Lutz MP, Domino EF. Structure activity relations of some indolealkylamines in comparison to phenethylamines on motor activity and acquisition of avoidance behavior. Psychopharmacology (Berl) 1974; 36:49-58. [PMID: 4525044 DOI: 10.1007/bf00441381] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Talalaenko AN. Analysis of adrenergic and serotoninergic structures of central components of the shaking and flexor reflexes in rabbits. Bull Exp Biol Med 1971; 72:772-775. [DOI: 10.1007/bf00788606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Meldrum BS, Bhargava VK. Excitant and depressant actions of some new alkoxy derivatives of 2-aminomethyl-1, 4-benzodioxane on the central nervous system of the rabbit. Int J Neuropharmacol 1968; 7:253-63. [PMID: 5720516 DOI: 10.1016/0028-3908(68)90032-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Marley E, Morse WH. Effects of alpha-methyl derivatives of noradrenaline, phenethylamine and tryptamine on operant conditioning in chickens. Br J Pharmacol Chemother 1967; 31:367-89. [PMID: 6083114 PMCID: PMC1557351 DOI: 10.1111/j.1476-5381.1967.tb00405.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Orientierende Übersicht. Rev Physiol Biochem Pharmacol 1966; 58:1-580. [DOI: 10.1007/bf02457096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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PSCHEIDT GR. Monoamine Oxidase Inhibitors. INTERNATIONAL REVIEW OF NEUROBIOLOGY 1964; 6:191-229. [PMID: 14285435 DOI: 10.1016/s0074-7742(08)60268-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2023]
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