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5-Hydroxytryptophan-induced myoclonus in guinea pigs: mediation through 5-HT1/2 receptor subtypes.

Abstract
In guinea pigs, myoclonus can be induced by 5-hydroxytryptamine (5-HT, serotonin) precursors and synthetic 5-HT receptor agonists, yet the receptor subtype specificity of this behavior is not fully delineated. Guinea pigs were pre-treated with carbidopa (50 mg) followed by one of eight 5-HT antagonists: (-)-N-tert-butyl-3-[4-(2-methoxyphenyl) piperazin-1-yl]-2-phenyl propionamide ((-)-WAY 100135) (5-HT1A), N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]-ethyl]-N-(2-pyridyl)-cy clohexancarboxamide (WAY 100635) (5-HT1A), methiothepin mesylate (5-HT1/2), mesulergine hydrochloride (5-HT2A/2C), N[4-methoxy-3-(4-methyl-L-piperazinyl)phenyl]-2'-methyl-4'-(5-methyl-1,2 ,4-oxadizol-3-yl) (GR 127935) (5-HT1D), trans-4-[(3Z)3-(2-dimethylaminoethyl)oxyimino-3(2-fluorop hen yl) propen-1-yl]phenol, hemifumarate (SR 46349) (5-HT2), ondansetron hydrochloride (5-HT3), and [1-[2-[methylsulphonyl)amino]ethyl]-4-piperidinyl]methyl-5-fluoro-2-meth oxy-1H-indole-3-carboxylate (GR 125487) (5-HT4). Thirty minutes later, they received 5-hydroxytryptophan (5-HTP) (75 mg/kg, sc) and myoclonic jumping rates were assessed every 10 min for 200 min by a blinded observer. Repeated measures analysis of variance of drug-induced antagonism of 5-HTP-induced myoclonus revealed a significant effect for the 5-HT receptor antagonists methiothepin mesylate, GR127935, and mesulergine hydrochloride compared to placebo, and each of these drugs inhibited 5-HTP-induced myoclonus in a dose-dependent fashion. Based on the receptor profiles of the three effective antagonists, 5-HTP-induced myoclonus is influenced by the 5-HT1/2 receptor systems. The absence of a significant change with any other receptor subtype antagonist suggests that myoclonus is not related to diffuse activation of central serotonergic mechanisms.
AuthorsE J Pappert, C G Goetz, G T Stebbins, M Belden, P M Carvey
JournalEuropean journal of pharmacology (Eur J Pharmacol) Vol. 347 Issue 1 Pg. 51-6 (Apr 17 1998) ISSN: 0014-2999 [Print] Netherlands
PMID9650847 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)
Chemical References
  • Ergolines
  • Oxadiazoles
  • Piperazines
  • Receptors, Serotonin
  • Serotonin Antagonists
  • GR 127935
  • Serotonin
  • Methiothepin
  • mesulergine
Topics
  • Animals
  • Dose-Response Relationship, Drug
  • Drug Interactions
  • Ergolines (pharmacology)
  • Guinea Pigs
  • Male
  • Methiothepin (pharmacology)
  • Myoclonus (chemically induced, drug therapy)
  • Oxadiazoles (pharmacology)
  • Piperazines (pharmacology)
  • Receptors, Serotonin (classification, drug effects, physiology)
  • Serotonin (toxicity)
  • Serotonin Antagonists (pharmacology)
  • Substrate Specificity

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