The anorectic action of peripherally administered 5-HT is enhanced by vagotomy.
Peripherally administered 5-HT produced a greater suppression of food intake in rats with subdiaphragmatic vagotomy than in sham-operated controls. The enhanced anorexia to 5-HT in vagotomised rats and the anorexia in sham-operated controls were reversed by methysergide, indicating the involvement of 5-HT receptors in the observed anorexia in both groups of animals. Thus the increased suppression of food intake in vagotomised rats cannot be explained in terms of non-specific effects of 5-HT. Both vagotomised and sham-operated rats showed an equivalent degree of anorexia when treated with fenfluramine suggesting that the receptor mechanism responsible for the anorectic action of 5-HT plays little or no part in the action of fenfluramine. Systemic administration of 5-HT was found to slow the rate of gastric clearance. Unlike the anorexia induced by 5-HT this effect was not reversed by methysergide. Thus it appears that peripherally administered 5-HT interacts with the vagus nerve but the mechanism responsible for 5-HT anorexia is independent of any action on gastric clearance.
D000818:Animals; D001067:Appetite Depressants / Q000494:pharmacology*; D004347:Drug Interactions; D004435:Eating / Q000187:drug effects; D005277:Fenfluramine / Q000494:pharmacology; D005746:Gastric Emptying / Q000187:drug effects; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D051381:Rats; D011985:Receptors, Serotonin / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology*; D014628:Vagotomy; D014630:Vagus Nerve / Q000187:drug effects*
D001067:Appetite Depressants; D011985:Receptors, Serotonin; D005277:Fenfluramine; D012701:Serotonin; D008784:Methysergide