Pre-test epinephrine injections reverse DDC-induced retrograde amnesia.

The effects of pre-test systemic administration of epinephrine on DDC-induced retrograde amnesia (RA) for discriminated Pavlovian fear-conditioning were examined in rats. Epinephrine reversed RA with the optimal dosage being 0.05 mg/kg. Apparently, the effect was specifically reversal of amnesia since (a) performance was restored to control levels, but no higher, and (b) sensitization and activity-related artifacts were minimized. These results are consistent with those showing reversal of RA by pre-test administration of hormones or catecholamine agonists. That is, they suggest that amnesia is due to a retrieval deficit rather than to failure of memory storage. Results are discussed in terms of epinephrine-induced modulation of storage and retrieval processes through central and peripheral mechanisms.