Abstract
LHRH analogue [(D-Ala6-desGly10) LHRH ethylamide] injection at a dose of 30μg/kg body weight accelerated spermiation in carp. The amount of collectable milt increased rapidly at 12h after injection and was maintained at high levels for 24h. The spermatocrit gradually in-creased throughout the experiment, and motility of the spermatozoa did not appear to be affected.
Plasma gonadotropin (GtH) level showed a significant rise at 5min after the LHRH analogue injection. The level decreased at 40min but increased again gradually and reached a peak at 24h. The control group had a lower plasma GtH level than the injected group throughout the experiment. Plasma testosterone increased significantly from 1h and was maintained at a high level for 24h. Plasma 11-ketotestosterone also showed a similar pattern of changes. No signi-ficant changes were recognized for both androgens in the control fish.
From these results, it is possible to postulate that exogenous LHRH analogue stimulated an early and rapid discharge of gonadotropin from the pituitary gland, and that spermiation was enhanced by the action of the successive secretion of gonadotropin and androgens.
