Learning-induced changes in D2 receptors of rat brain are sexually dimorphic.

Pharmacological agents known to stimulate monoamine systems improve memory, and destruction of the dopaminergic systems or dopamine depletion lead to impairments in various learning-related tasks. These reported effects of the central dopaminergic system imply the involvement of D2 receptors. The aim of the present study was to investigate changes in [3H]spiroperidol binding in seven areas of rat brain following informal and active avoidance learning. Littermate male and female rats were reared until 3 months of age in standard colony conditions and treated as active controls or in enriched environmental conditions and exposed to pole-jump active avoidance trials. Female rats acquired avoidance behavior more rapidly than males. Among the brain regions, only the hippocampus showed significant variations in D2 receptor binding between the groups; sex differences and learning-sex interaction were observed in the corpus striatum. There was an inverse correlation between learning performance and hippocampal D2 receptor binding. Our results show that learning affects hippocampal D2 receptors in a sexually dimorphic pattern.