Effect of Orexin in Ventromedial and Lateral Hypothalamus on Aromatse Gene Expression and 17- β Estradiol Concentration

Previous studies have investigated the effects and importance of orexin and estradiol on food intake. In this study the effects of orexin on estradiol release by the ventromedial hypothalamus (satiety center) and lateral hypothalamus (feeding center) have been investi­gated. Forty adult male rats، divided to two groups، the control group (consisting of 10 rats) and an experimental group (consisting of 30 rats)، were canulated in the lateral area and ventromedial nucleus steriotaxically. After two days recovery، 1،2 and 4 micrograms of orexin were injected into the lateral area and ventromedial nucleus. After two hours، tissue of the lateral area and ventromedial nucleus were removed and concentrations of estradiol and aromatase were measured by radio-immuno assay and RT-PCR، respectively. Results of RT-PCR showed that orexin-A (1،2،4 µg) augmented aromatase gene expression in the VMH and LH. 17-β estradiol measurement showed that 1، 2 and 4 µg orexin infusion increased estradiol levels significantly in VMH and LH، especially the 2 and 4 µg doses، observations suggesting that the neurons secreting estradiol exist in the VMH and LH.