EFFECTS OF CORTICOTROPIN-RELEASING FACTOR ON BRAIN SEROTONERGIC ACTIVITY

The serotonergic dorsal raphe nucleus is innervated by corticotropin-r eleasing factor (CRF) and expresses CRF receptors, suggesting that end ogenous CRF impacts on this system. The present study characterized in teractions between CRF and the dorsal raphe serotonin (5-HT) system. T he effects of intracerebroventricularly (i.c.v.) administered CRF on m icrodialysate concentrations of 5-HT in the lateral striatum of freely moving rats were determined. CRF had biphasic effects, with 0.1 and 0 .3 mu g decreasing and 3.0 mu g increasing 5-HT dialysate concentratio ns. I.C.V. administration of CRF inhibited neuronal activity of the ma jority of dorsal raphe neurons at both low (0.3 mu g) and high (3 mu g ) doses. Likewise, intraraphe administration of CRF (0.3 and 1.0 ng) h ad predominantly inhibitory effects on discharge rate. Together, these results suggest that CRF is positioned to regulate the function of th e dorsal raphe serotonergic system via actions within the cell body re gion. This regulation may play a role in stress-related psychiatric di sorders in which 5-HT has been implicated. (C) 1998 American College o f Neuropsychopharmacology. Published by Elsevier Science Inc.