Effects of Dopamine,Estradiol and Testosterone on Gonadotropin Release From The Pituitary Fragments of Rana rugulosa

To understand the regulatory mechanisms of gonadotropin secretion in Rana rugulosa,this study investigated the effects of dopamine (DA),estradiol (E2) and testosterone (T) on the in vitro release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary fragments of female Rana rugulosa using a static incubation system and radio-immunoassay (RIA).The results indicated that DA at the concentration from 0.1 μmol/L to 10 μmol/L inhibited the release of LH and FSH from the pituitary fragments of sexually pre-mature or hibernating individuals,and the inhibitory effects enhanced with increasing concentrations of DA.E2 at 1 μmol/L and 10 μmol/L significantly stimulated the release of LH of sexually pre-mature individuals,but inhibited their FSH release at 0.1 μmol/L to 10 μmol/L;T had no obvious effects on their FSH release,but significantly inhibited their LH release at 10 μmol/L.Neither E2 nor T,at the concentration from 0.1 μmol/L to 100 μmol/L,had obvious effects on the release of LH and FSH of hibernating individuals.The data suggest that DA and sexual steroids may have direct regulatory actions on LH and FSH release at the pituitary level in Rana rugulosa,and the action of sexual steroids may relate to the gonadal development stages (seasons).