Similar effects of a monoamine oxidase inhibitor and a sympathomimetic amine on memory formation

Abstract

Amnesia resulting from inhibition of cerebral protein synthesis by cycloheximide can be prevented by subcutaneous injection of the monoamine oxidase inhibitor pargyline (25 mg/kg) or the sympathomimetic amine metaraminol (3.0 mg/kg) administered up to 30 min following learning of a single trial passive avoidance task in day-old chickens. The injection has to be made during the life time of labile memory for the prevention of cycloheximide-induced amnesia. On the other hand amnesia induced by the Na/K ATP'ase inhibitor ouabain can only be prevented if these two agents are administered up to 5 min after learning, i.e. during the life time of short-term memory. In addition, both agents produce a retrieval deficit 90 min after the injection, but only when memory is in long-term storage. These results are compared to those obtained with administration of norepinephrine, d-amphetamine and diphenylhydantoin.