Modulation of social learning in rats by brain corticotropin-releasing factor

In order to investigate the impact of brain stress-related neuropeptide tone on learning and memory performance, juvenile recognition ability was examined in adult female rats using a social memory test following pharmacological inactivation and activation of corticotropin-releasing factor (CRF) systems. In particular, administration of a competitive CRF receptor antagonist [0.2, 1 or 5 microg intracerebroventricular doses of D-Phe CRF (12-41)], dose dependently impaired learning performance over a 30-min delay to 27% of vehicle controls values. In complementary fashion, forgetting produced by a 120-min delay that impaired social recognition performance to 29% of 30-min delay control levels was reversed by administration of a 1-microg dose of the CRF binding protein ligand inhibitor, r/h CRF (6-33), although a higher 5 microg dose exerted non-specific effects on social investigation. These findings suggest that brain CRF systems are physiologically relevant for social memory capacity in the absence of stressor exposure.