Long-term effects of a luteinizing hormone-releasing hormone analogue and/or a dopamine antagonist, pimozide, on gonadal activity in an autumn-spawning bitterling,Acheilognathus rhombea, during various phases of the annual reproductive cycle
✍ Scribed by Shimizu, Akio
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 844 KB
- Volume
- 276
- Category
- Article
- ISSN
- 0022-104X
No coin nor oath required. For personal study only.
✦ Synopsis
An autumn-spawning bitterling, Acheilognathus rhombea, kept mainly under suppressive environmental conditions, was treated with an emulsified luteinizing hormone-releasing hormone (LHRH) analogue (LHRH-a) and/or a dopamine antagonist, pimozide (PIM), in various phases throughout the annual reproductive cycle. In the experiments performed under long (suppressive) day length using prespawning immature underyearling fish in late summer, LHRH-a stimulated gonadal development to some extent but could not induce functional maturity. However, administration of LHRH-a with PIM was effective for stimulation of gonadal activity, attaining functional maturity in both sexes. Photorefractory yearling fish in spring showed induction of functional maturity by administration of LHRH-a + PIM under the short day length but not under the long day length. LHRH-a + PIM treatment had no effect on maintenance of gonadal maturity in fish regressing under low (suppressive) temperature during early winter. It was concluded that the involvement of gonadotropin-releasing hormone (GnRH) and the dopamine antagonist in longterm reproductive events greatly differed among reproductive phases constituting the annual reproductive cycle and/or among environmental conditions concerned with the regulatory mechanism of the cycle. Interaction of GnRH and gonadotropin release-inhibiting factor (GRIF) is important for the regulation of long-term reproductive events in this species. Nonetheless, photoperiod or temperature may still have some effect which cannot be compensated for by the GnRH or the GRIF antagonists, especially in fish during the refractory period and in fish regressing under low temperature conditions. @ 1996 Wiley-Liss, Inc.