ESTRADIOL REGULATION OF NITRIC-OXIDE SYNTHASE MESSENGER-RNAS IN RAT HYPOTHALAMUS

Expression and estrogen regulation of the genes for nitric-oxide (NO)- synthesizing enzymes (NO synthase, NOS) were investigated by in situ h ybridization. This study focused on regions of the hypothalamus that c ontain estrogen receptors and regulate specific neuroendocrine functio ns related to female sexual behavior and food intake, among others. Ov ariectomized (OVX) rats were treated with vehicle or 3 mu g/100 g estr adiol benzoate (EB) for 7 days. Brains were sectioned and hybridized w ith antisense riboprobes for neuronal NOS, macrophage NOS and endothel ial NOS. In the hypothalamus, mRNA was clearly detectable only for the neuronal NOS with the probes used. A strong hybridization signal was observed in the supraoptic paraventricular and ventromedial nuclei (SO N, PVN and VMN, respectively). Quantitative analysis showed an increas e in neuronal NOS mRNA in the VMN of the OVX rats treated with EB. The increase was mainly in the ventrolateral aspect of the VMN. No signif icant changes were observed in the hypothalamic SON and PVN. The data suggest that the expression of neuronal NOS mRNA in VMN can be regulat ed by estrogen.