sincalide and 5-carboxamidotryptamine

These studies compared the effects of total abdominal vagotomy (VGX) on ingestive actions produced by peripheral serotonergic and cholecystokinergic (CCKergic) stimulation in rats. Subcutaneous injection of 0.01-0.16 mumol/kg of the serotonin (5-HT) analogue 5-carboxamidotryptamine (5-CT) dose-dependently reduced mash intake equally in VGX rats and their laparotomized (LAP) controls but concurrently stimulated drinking only in the controls. The sulfated octapeptide of cholecystokinin (CCK-8, 4.0 nmol/kg ip) also reduced food intake only in the controls. In a second set of rats, vagotomy did not alter anorexia after intraperitoneal administration of either 2.0 or 8.0 mumol/kg of 5-HT or of 0.03 mumol/kg of 5-CT but abolished anorexia after a large dose of CCK-8 (8.0 nmol/kg). The completeness of vagotomy was verified histologically by immunohistochemical staining of the vagal bundles for the high molecular weight form of neurofilament-H protein. We report for the first time that 5-CT produces anorexia by a vagally independent mechanism. In contrast, 5-CT stimulates drinking by a pathway that does involve vagal function. Finally, we confirm the prediction that vagotomy dissociates the neural mechanisms for the anorectic action of peripheral 5-HTergic and CCKergic stimulation.

Topics: Abdomen; Animals; Anorexia; Cholecystokinin; Dose-Response Relationship, Drug; Eating; Male; Rats; Rats, Sprague-Dawley; Serotonin; Serotonin Receptor Agonists; Sincalide; Thirst; Vagotomy