Effects of 5-hydroxytryptamine on cat spinal motoneurons.
The effects of 5-hydroxytryptamine (5-HT) on spinal motoneurons were examined in pentobarbital-anaesthetized cats and in nonanaesthetized decerebrate cats by intracellular recording and extracellular iontophoresis of 5-HT. 5-HT first induced a depolarization and then a long-lasting hyperpolarization (up to 60 min) with unchanged input resistance. The slow hyperpolarization was prevented by the 5-HT antagonists ketanserin (5-HT2), methysergide, and spiperone (5-HT1,2) and mimicked by the agonist (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (5-HT2). The post-spike after hyperpolarization was enhanced after application of 5-HT. A depolarization was induce by the 5-HT agonists (+/-)-8-hydroxy-(2)-(di-n-propylamino)tetralin (5-HT1A) and 1-(2-methoxyphenyl)piperazine (5-HT1). Possible mechanisms for the 5-HT-induced hyperpolarization and its intracellular medication are discussed. The present data suggest multiple effects of 5-HT on cat spinal motoneurons.
Zhang
L
L
Department of Anaesthesia Research, McGill University, Montréal, Qué., Canada.
D000200:Action Potentials / Q000187:drug effects; D000758:Anesthesia; D000818:Animals; D002415:Cats; D003655:Decerebrate State; D007478:Iontophoresis; D009046:Motor Neurons / Q000187:drug effects*; D010424:Pentobarbital; D012701:Serotonin / Q000494:pharmacology* / Q000502:physiology; D012702:Serotonin Antagonists / Q000494:pharmacology; D013116:Spinal Cord / Q000166:cytology*
D012702:Serotonin Antagonists; D012701:Serotonin; D010424:Pentobarbital