Effects of chronic corticosterone treatment on electrophysiological and behavioral measures in the rat

The electrophysiological and behavioral effects of daily oral exposure to a corticosterone or vehicle solution was evaluated in 20 male Wistar rats over a 10-wk period. Evaluation of the rats' behavior in an open field apparatus, as well as in automated locomotor cages, revealed no significant differences between steroid-treated and control animals following 5-6 wk of exposure. No differences in mean EEG power, as estimated by spectral analysis of cortical and dorsal hippocampal recordings, were observed between the two groups following 8 wk of exposure. However, some increases in EEG "stability" were noted in the corticosterone-treated rats. At 9 wk, responses to auditory stimuli, as assessed by evoked responses, in cortex and dorsal hippocampus were also found to be unaltered by corticosterone exposure. These studies suggest that exposure to daily oral corticosterone, in the doses used, over a period of 2-3 mo is not associated with gross electrophysiological or spontaneous behavioral effects in the brain areas assessed.