Interaction of β-endorphin and GABAergic drugs in the regulation of memory storage

These experiments examined the interaction of β-endorphin and GABAergic drugs, administered post-training, in influencing retention of an inhibitory avoidance response. Male CD1 mice were trained in an inhibitory avoidance task, given immediate post-training ip injections and tested 24 h later for retention. β-Endorphin (0.5, 1.0, or 2.0 μg/kg) and muscimol (0.5, 1.0, or 2.0 mg/kg) produced dose-dependent impairment of retention; picrotoxin (0.25, 0.5, or 1.0 mg/kg) and bicuculline (0.1, 0.25, or 0.5 mg/kg) produced dose-dependent enhancement of retention. A low subeffective dose of muscimol (0.5 mg/kg) potentiated the retention-impairing effect of β-endorphin (1.0 μg/kg). In addition, concurrent administration of low, subeffective doses of bicuculline (0.1 mg/kg) or picrotoxin (0.25 mg/kg) attenuated the retention-impairing effects of β-endorphin (1.0 μg/kg). The findings are consistent with previous evidence indicating that β-endorphin influences memory through an interaction with GABAergic mechanisms.