ACTIONS OF THE SUPERACTIVE ANALOGUE DESGLY10 (D-ALA6) LRH ETHYLAMIDE (LRH-A) ON GONADOTROPIN SECRETION IN GOLDFISH (CARASSIUS AURATUS)

The effects of season, temperature, dosage, frequency of injection and interval between injections on the GtH release-response to LRH-A in goldfish were investigated. The results demonstrated that goldfish have a very dramatic seasonal variation in responsiveness to LRH-A. The highest serum GtH levels induced were just prior to the spawning season in early spring (February.) Following the spring spawning season (May-June), the GtH release-response was less, and, in the summer (August)when the fish were sexually regressed, there was little or no response. A dose dependence was not always clear in the response, but high dose (1.0 ug/g body weight) usually induced the highest levels and had a persistent effect for 24 hours. The pituitary GtH level was significantly lower after a series of injections of high dose. There is a close relationship between the level of serum GtH induced, and temperature, the dosage of LRH-A injected, the interval between injections.Daily injections of LRH-A for up to 9—10 days can stimulate onset of gonadal recrudes.cence in sexually regressed goldfish; however, it may slow down or block gonadal recrudescence in goldfish that have commenced development.