The cholinergic and dopaminergic systems of the prelimbic sector of frontal cortex and memory in the rat.

Rats were trained to perform delayed non-matching to sample (a working/representational memory task) and visual discrimination (a reference/dispositional memory task) in a T-maze, and implanted bilaterally with cannulae in the prelimbic cortex. The rats were tested postoperatively after bilateral 1-microliter injections of vehicle (Krebs-Ringer), sulpiride (10 micrograms/microliter) or scopolamine (18 micrograms/microliter). Sulpiride had no effect on the performance of either task, whereas scopolamine interfered only with the performance of delayed non-matching to sample. We conclude that dopaminergic mechanisms in the prelimbic cortex are not involved in either type of memory and that cholinergic, but not dopaminergic, mechanisms are important for working/representational memory processes.