5-Hydroxytryptamine and learning: long-term effects of P-chloroamphetamine on acquisition.

The effect of p-chloroamphetamine (PCA) on the acquisition of a conditioned avoidance response in the rat was examined. Eleven rats were injected with saline or 2 X 10 mg/kg of PCA i.p. on two consecutive days and the learning procedure was started eight days later and lasted for six days. The acquisition of the conditioned avoidance response was strongly impaired by PCA compared with the control group. It is suggested that the impaired learning is due to a long-term effect of PCA on a 5-hydroxytryptamine system directly or indirectly linked to learning.