ABDOMINAL VAGOTOMY DISSOCIATES THE ANORECTIC MECHANISMS FOR PERIPHERAL SEROTONIN AND CHOLECYSTOKININ

These studies compared the effects of total abdominal vagotomy (VGX) o n ingestive actions produced by peripheral serotonergic and cholecysto kinergic (CCKergic) stimulation in rats. Subcutaneous injection of 0.0 1-0.16 mumol/kg of the serotonin (5-HT) analogue 5-carboxamidotryptami ne 5-CT) dose-dependently reduced mash intake equally in VGX rats and their laparotomized (LAP) controls but concurrently stimulated drinkin g only in the controls. The sulfated octapeptide of cholecystokinin (C CK-8, 4.0 nmol/kg ip) also reduced food intake only in the controls. I n a second set of rats, vagotomy did not alter anorexia after intraper itoneal administration of either 2.0 or 8.0 mumol/kg of 5-HT or of 0.0 3 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 histological ly by immunohistochemical staining of the vagal bundles for the high m olecular weight form of neurofilament-H protein. We report for the fir st 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 diss ociates the neural mechanisms for the anorectic action of peripheral 5 -HTergic and CCKergic stimulation.