Chronic corticosterone treatment impairs spontaneous alternation behavior in rats.

The present study used behavioral and morphological measures to assess hippocampal integrity in adult male rats after 8 weeks of daily corticosterone (10 mg/kg) injections. Behavioral testing during the final week of treatment revealed that spontaneous alternation behavior, a behavioral marker of hippocampal damage, was reduced in experimental animals without influencing exploration. Physiological assessment indicated that steroid exposure produced functional changes characteristic of prolonged exposure to stress or elevated plasma corticosterone, i.e., lower body weight and thymic involution. However, hippocampal cell loss was not observed in experimental rats. The data suggest that prolonged elevation of plasma corticosterone may significantly disrupt a hippocampal-sensitive behavior without producing gross morphological changes.