Corticotropin-releasing factor (CRF) administered intraventricularly (0.5 nmol) was found to increase the discharge rates of locus coeruleus (LC) neurons in anesthetized rats. A similar effect on discharge rate was also observed during direct application of CRF to LC neurons by pressure microapplication. Intraventricular administration of CRF-OH, previously demonstrated to be considerably less potent in releasing ACTH, did not alter LC firing rates. These data suggest that activation of these central noradrenergic neurons may constitute an integral part of the overall 'stress response' initiated by CRF release.