INFUSION OF THE SEROTONIN(1B) (5-HT1B) AGONIST CP-93,129 INTO THE PARABRACHIAL NUCLEUS POTENTLY AND SELECTIVELY REDUCES FOOD-INTAKE IN RATS

Unilateral infusion of the selective 5-HT1B agonist, CP-93,129 (3-(1, 2, 5, 6,-tetrahydropyrid-4-yl) pyrrolo[3,2-b]pyrid-5-one) into the par abrachial nucleus (PBN) of the pens reduced food consumption by rats. The hypophagia was dose-related (ED50 approximate to 1 nmol) and assoc iated with fewer observations of feeding and more periods of inactivit y. Water intake, grooming and exploratory activity were unaffected. CP -93.129 also decreased food intake when injected into the hypothalamic paraventricular nucleus, but this action was 50-fold less potent than administration into the PBN. Autoradiography demonstrated 5-HT1B site s in the PBN: this binding was displaced by CP-93,129. The results imp licate parabrachial 5-HT1B receptors in mediating serotonergic enhance ment of satiation.