This study examines the roles of PKC and protein phosphorylation in the retention performance of a passive avoidance learning (PAL) task in rats. Results revealed that H7 injected into the dentate gyrus (DG) of the hippocampus impaired retention in a dose-dependent manner. Corticotropin-releasing factor (CRF) injected into the DG improved retention and this facilitation was antagonized by H7 pretreatment. CRF increased phosphorylation of five proteins, whereas H7 decreased phosphorylation in three of these proteins in both the cytosol and the membrane fractions of hippocampus. These effects were shown not to be associated with stress. These results demonstrate that CRF increased protein phosphorylation associated with enhanced retention of PAL task in rats.