Despite abundant evidence that systemic administration of adrenergic drugs and hormones can produce retrograde memory enhancement, the literature contains no clear demonstration that postlearning systemic administration of adrenergic antagonists produces retrograde amnesia. Here we demonstrate retrograde amnesia for a stressful learning task (a spatial water maze) with systemic administration of the beta-adrenergic antagonist propranolol (5 mg/kg). The amnesic effect of the drug depended on the degree of learning in the subjects: Propranolol caused a robust retrograde amnesia in "good learners," but did not significantly affect memory in "poor learners." The findings provide critical additional support for the hypothesis that postlearning adrenergic activation modulates memory consolidation processes after emotionally stressful events and help explain previous failures to detect memory impairment after systemic administration of adrenergic blocking drugs.
Copyright 2000 Academic Press.