Environmental enrichment selectively increases 5-HT1A receptor mRNA expression and binding in the rat hippocampus

Environmental enrichment augments neuronal plasticity and cognitive function and possible mediators of these changes are of considerable interest. In this study, male rats were exposed to environmental enrichment or single housing for 30 days. Rats from the enriched group had significantly higher 5-HT1A receptor mRNA expression in the dorsal hippocampus (62%, 59% and 44% increase in the CA1, CA2 and CA3 subfields, respectively). This was associated with significantly higher [3H]8-OH-DPAT binding in the inferior part of CA1. No changes were seen for 5-HT2A or 5-HT2C receptor mRNAs. The neuronal plasticity detected after environmental change may be mediated, in part, through 5-HT1A receptors.