ANDROGENS SELECTIVELY MODULATE C-FOS MESSENGER-RNA INDUCTION IN THE RAT HIPPOCAMPUS FOLLOWING NOVELTY

We have previously shown that androgen receptors are found in high con centrations in hippocampal CA1 pyramidal cells. To begin to explore th e possible roles for androgen receptors in this area of the brain, we studied the effects of endogenous and exogenous androgen on the behavi ourally induced expression of cellular immediate early gene messenger RNAs. Adult male Fischer 344 rats were either gonadectomized, gonadect omized and given two Silastic capsules of dihydrotestosterone propiona te at the time of surgery, or left intact. Three weeks later, animals were placed into a novel open field for 20 min. This behavioural parad igm caused region- and gene-specific increases of c-fos, jun-B, c-jun and cif268 messenger RNA in the hippocampus as determined by semi-quan titative in situ hybridization histochemistry. The removal of circulat ing androgen by gonadectomy potentiated, whereas dihydrotestosterone t reatment of castrates attenuated, the behaviourally induced expression of c-Sos messenger RNA in the CAI region of the hippocampus. No chang es in c-Jos messenger RNA expression were detected in the CA3 or denta te gyrus regions where androgen receptor levels are low. Androgen stat us did not affect either the basal or stimulated expression of Jun-B, C-Jun or zif268 messenger RNA in any of the three cellular regions of the hippocampus examined. These results implicate androgen receptors i n modulating the active response of hippocampal neurons to a behaviour ally relevant stimulus. Since the products of cellular immediate genes can Function to alter an array of downstream genes, the modulation of these genes in the hippocampus by gonadal hormones may have important ramifications for hippocampal function. Copyright (C) 1996 IBRO.