Physostigmine accelerates the development of associative memory processes in the infant rat.

Previous research has shown that 15-day-old rats are quite poor at associating temporally separated events. However, by 17 days of age, this capability has improved substantially (Moye and Rudy 1987a). In the present study, the centrally active anticholinesterase physostigmine was found to enhance the ability of 15-day-olds to associate a tone conditioned stimulus (CS) with a shock unconditioned stimulus (US) when these events were separated by a 10-s trace interval. In effect, the drug produced trace conditioning performance similar to that observed in older animals. We suggest that performance in the trace conditioning task requires the development of associative memory processes that allow the young rat to retain a representation of a CS over time. Furthermore, the enhancement of trace conditioning by physostigmine indicates that central cholinergic maturation is an important factor in the expression of associative memory.