5-Hydroxytryptamine depresses depolarizing responses to GABA in the rat isolated vagus nerve.
Axons of the rat isolated cervical vagus nerve responded to gamma-aminobutyric acid (GABA) and 5-hydroxytryptamine (5-HT) with a readily reversible dose-dependent depolarization. Prior application of 5-HT at 2 or 30 microM equally depressed the depolarizing responses to GABA, shifting the GABA dose-response curve to the right and depressing the maximum; by contrast, responses to 5-HT were affected only by large doses of GABA (greater than 300 microM), and to a lesser degree. In addition, the fade in responses to high doses of GABA was also reduced in the presence of 5-HT. It is suggested that such all-or-none depressive actions may explain the blockade of GABA-induced responses by 5-HT observed in other tissues such as the guinea-pig ileum.
D000818:Animals; D004558:Electric Stimulation; D018756:GABA Antagonists; D066298:In Vitro Techniques; D008297:Male; D009467:Neuromuscular Depolarizing Agents / Q000037:antagonists & inhibitors*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000494:pharmacology*; D014630:Vagus Nerve / Q000187:drug effects*
D018756:GABA Antagonists; D009467:Neuromuscular Depolarizing Agents; D012701:Serotonin