Corticotropin-releasing factor (CRF) and the urocortins (UCN1, UCN2 and UCN3) are structurally related neuropeptides which act via two CRF receptors (CRF1 and CRF2) with putatively dualistic actions in the brain. The aim of the present study was to investigate the effects of CRF agonists, such as CRF, UCN1, UCN2, and UCN3, and CRF antagonists, such as antalarmin (a selective CRF1 antagonist) and astressin2B (a selective CRF2 antagonist) on the release of noradrenaline (NA) in the locus coeruleus (LC) and serotonin (5HT3) in the raphe nuclei (RN). For this purpose, male Wistar rats were used, their LC and RN were isolated, dissected and incubated with 5 μM of tritium-labelled NA and 5HT3 , then superfused with 100 nM of CRF, UCN1, UCN2 and UCN3 and stimulated electrically. In order to determine which receptor mediates the effects of CRF and urocortins 0.1 nM of antalarmin and 1 nM of astressin2B were also administered. In the LC, the NA release was increased significantly by CRF and UCN1 and decreased significantly by UCN2. In the RN, the 5HT3 release was reduced significantly by CRF and UCN1 and enhanced significantly by UCN3. The effects of CRF and UCN1 were prevented only by selective CRF1 antagonist, whereas the effects of UCN2 and UCN3 were reversed only by selective CRF2 antagonist. Therefore, the present study suggests the existence of two distinct CRF systems (CRF1 vs CRF2) in the LC and RN, which exert dualistic and site-specific effects on the local release of NA and 5HT3, respectively.