THE INDUCTION AND SUPPRESSION OF C-FOS EXPRESSION IN THE RAT-BRAIN BY CHOLECYSTOKININ AND ITS ANTAGONIST L364,718

Immunohistochemical techniques were used to map c-fos expression in the rat brain after the i.p. administration of CCK-8 (8 mug/kg). C-fos expression was observed in the rostral and the caudal parts of the nuclei of the solitary tract (NTS), and the paraventricular nuclei (PVN) in the hypothalamus. The c-fos expression in these areas was suppressed by the administration of L364,718 (120 mug/kg). Since L364,718 is known to be a powerful selective antagonist to the peripheral CCK-A receptors, these data suggest that the effects produced by exogenous CCK are due to peripheral receptors that project to the NTS.