EFFECTS OF THREE DIFFERENT GONADOTROPIN - RELEASING HORMONE ANALOGUES COMBINED WITH DOPAMINE ANTAGONISTS ON PLASMA SEX STEROID HORMONES, IN ENDANGERED MALE AND FEMALE CASPIAN BROWN TROUT, SALMO TRUTTA

To understand the steroidogenic activities in Caspian brown trout, female and male broodstocks were injected with three different GnRHa in combination with two different dopamine antagonists and we examined changes in plasma sex steroid hormones during the experiments. In four separate experiments, female and male received two injections (at 0 day and 4 day) in total volume 0.5 and 0.25 ml per kg-1 body weight respectively. Control group received only propylene glycol (Vehicle only). The final concentrations of GnRHa and metoclopramide (MET) were 20 µg GnRHa kg-1 body weight (BW) and 10 mg kg-1 body weight (BW), respectively. Each injection, received half dose of hormone. Blood samples were taken at 0, 2, 5 and 7 days, and blood plasma was retained for analysis of steroid levels. In female, plasma levels of estradiol-17B (E2) and testosterone (T) showed significant decreases in fish treated with GnRHa plus Dopamine antagonist compared to control group. Plasma 17?,20B-dihydroxy-4-pregnen-3-one (17,20B-P) levels abruptly increased at the 2nd day post-injection in all treated groups, reached peak levels at the 5th day, and the elevated levels slightly decreased by the 7th day. In male, all experimental treatments showed lower blood plasma 11-ketotestosterone (11KT) levels relative to control. Treatment in all hormonal groups resulted in significant decrease in blood plasma 17,20BP levels compared to control group except fish treated with mGnRHa in combination with metoclopramide at 2nd post injection. Mean blood plasma T levels displayed a marked increase between 2nd and 5thyad . Changes in plasma T levels showed no significant change at the 7th day post injection.