Diphenylhydantoin extension of short-term and intermediate stages of memory

Diphenylhydantoin was shown to extend the duration of maximum availability of both short-term and intermediate memory in day-old chicks following a single trial passive avoidance learning task. Diphenylhydantoin also extended the time of susceptibility of long-term memory to inhibition by cyloheximide, suggesting that the extention of the life of intermediate memory was accompanied by a delay in long-term memory formation. Furthermore, while diphenylhydantoin counteracted amnesia induced by cycloheximide given 5 min before or immediately after learning, it had no effect on amnesia induced by cycloheximide administered 5 min or later after learning. For the latter, a second injection of diphenylhydantoin was necessary. This is consistent with the argument that the first injection of diphenylhydantoin extended the life of intermediate memory and delayed the formation of long-term memory.