Administration of the α-adrenergic antagonist phentolamine into the amygdala complex of Sprague-Dawley rats was observed to alter memory processes in a time-dependent manner. Bilateral administration of phentolamine (8.5 nmole) into the amygdala immediately after training significantly increased retention of passive avoidance conditioning. Delayed administration of the same dose 6 hr after training did not significantly alter retention. In addition, whereas post-training administration of the β-adrenergic antagonist propranolol (34.0 nmole) into the amygdala significantly decreased retention, concurrent administration of phentolamine (8.5 nmole) and propranolol (34.0 nmole) resulted in normal retention. The effects of α- and β-adrenergic antagonist administration on memory processes are discussed in terms of a possible opposing effect of these agents on norepinephrine function within the amygdala complex.
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