Environmental enrichment increases glucocorticoid receptor expression in hippocampal pyramidal neurons, but the molecular mechanisms are unknown. Several transcription factors are expressed in hippocampal neurons where they respond to environmental stimuli. In this study 12 adult male rats (n = 6 in each group) were exposed to enriched or isolated environment for 30 days. The expression of AP-2 mRNA, studied by in situ hybridization, was attenuated by environmental enrichment in the CA2 and CA3 subfields of the hippocampus. AP-2 may be involved in the environmental effect of glucocorticoid receptor gene expression in these neurons.