Corticosterone -- an anxiogenic or an anxiolytic agent?

Corticosterone (3--12 mg kg-1, i.p., giving rise to plasma corticosterone concentrations from 26.7 to 89.0 micrograms/100 ml) failed to have a significant anxiogenic action. Instead, corticosterone (3 mg kg-1) had a significant anxiolytic effect in the social interaction test of anxiety. Adrenalectomized rats had very low levels of social interaction; but adrenalectomized rats that had been given replacement corticosterone therapy did not differ from the sham-operated controls. Thus, corticosterone appears to have the opposite effect to that previously reported for ACTH. Possible mechanisms for the observed results are discussed.