Effects of amphetamine on short-term, protein-independent, memory in day-old chickens.

When the protein synthesis inhibitor cycloheximide (CXM) is administered just before or soon after a single learning trial, the formation of permanent memory is prevented in day-old chickens. In spite of the blockage of long-term memory, which occurs by 3 hr, Mark and Watts [14] have demonstrated a short-term memory which is independent of protein synthesis and which decays over the 3 hr period. D-amphetamine sulphate, administered subcutaneously (up to 2 hr) after learning to CXM pretreated chickens, held the memory at the level exhibited by the labile memory trace at the time of injection. This close relationship between the amount of labile memory and the time of injection was still apparent 24 hr after learning. These data suggest that, provided there is sufficient labile memory in existence at the time of administration, amphetamine maintains the trace which would otherwise decay and allows it subsequent consolidation into permanent memory at a time later than normal.