| Title: | Enhancing spawning in the grey mullet (Mugil cephalus) by removal of dopaminergic inhibition |
| Author(s): | Aizen J; Meiri I; Tzchori I; Levavi-Sivan B; Rosenfeld H; |
| Address: | "Israel Oceanographic and Limnological Research, National Center for Mariculture, Eilat 88112, Israel" |
| DOI: | 10.1016/j.ygcen.2005.01.002 |
| ISSN/ISBN: | 0016-6480 (Print) 0016-6480 (Linking) |
| Abstract: | "A dot-blot immunoassay for the detection of vitellogenin (Vtg) in plasma of adult grey mullet (Mugil cephalus) was developed. The assay identified the sex of the tested fish prior to detectable gonadal development, enabling the establishment of broodstock at the desired ratio of 7:4 females to males. This broodstock was maintained under natural photoperiod, and used to study the relative effect of gonadotropin-releasing hormone (GnRH) and dopamine antagonists on oocyte maturation and ovulation, as well as the effect of 17alpha-methyltestosterone (MT) on spermiation. Three groups of females were treated with: (i) a single injection of dopamine antagonist, domperidone (Dom), (ii) GnRH analog (GnRHa) administered via ethylene-vinyl acetate copolymer (EVAc) slow-release implants or (iii) a combination of both Dom and GnRHa. Males were treated with MT, administered via EVAc slow-release implants. An additional group of untreated fish was used as a control. The Dom treatment proved to be more potent than the GnRHa treatment, and did not differ significantly from the combined treatment. The Dom and Dom+GnRHa treatments accelerated oocyte development and increased plasma estradiol levels equally, whereas the GnRHa treatment did not vary significantly from the control. MT was found to be a potent spermiating agent, which enhanced steady milt production in all treated males. In contrast, no spontaneous spermiation occurred in untreated males. Plasma 11-ketotestosterone (11-KT) levels were significantly higher in MT-treated males than in the controls. Interestingly, MT-treated males held with the GnRHa+Dom-treated females showed higher levels of plasma 11-KT than those held with GnRHa-treated females, indicating an additive effect which is probably attributable to female pheromones. Fully mature females were induced to spawn by injecting GnRHa alone or coupled with metaclopramide (a dopamine D2 receptors antagonist). The combined treatment, which included a dopamine antagonist, was found to be more potent in inducing ovulation and spawning as compared to GnRHa alone. In conclusion, our data suggest that dopaminergic inhibition is a major barrier along the reproductive axis that arrests spontaneous spawning in captive mullets" |
| Keywords: | "Animals Blotting, Western Domperidone/*pharmacology Dopamine/*physiology Dopamine Antagonists/*pharmacology Drug Implants Electrophoresis, Polyacrylamide Gel Female Gonadotropin-Releasing Hormone/pharmacology Immunoassay Male Methyltestosterone/pharmacolo;" |
| Notes: | "MedlineAizen, Joseph Meiri, Iris Tzchori, Itai Levavi-Sivan, Berta Rosenfeld, Hanna eng Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. 2005/05/03 Gen Comp Endocrinol. 2005 May 15; 142(1-2):212-21. doi: 10.1016/j.ygcen.2005.01.002. Epub 2005 Feb 3" |
