Dopaminergic influence on gonadotropin secretion in white sturgeon (Acipenser transmontanus)

Abstract

The effects of dopamine on the secretion of two sturgeon gonadotropins (stGTH I and stGTH II) in sexually mature male white sturgeon (Acipenser transmontanus) were evaluated. In Experiment I, sturgeon were given intraperitoneal injections of physiological saline (PS), dopamine (100 mg kg-'), the gonadotropin releasing hormone analog D-Ala 6 -des-Gly 10 -GnRH ethylamide (GnRHA) (10 jig/kg-'), and a combination of GnRHa and dopamine. Fish receiving only GnRHa had significantly higher (p < 0.05) concentrations of plasma stGTH I and stGTH II compared to fish receiving PS, dopamine, or a combination of GnRHa and dopamine. Two hours following its administration, dopamine was effective in decreasing plasma concentrations of both stGTHs that were previously elevated by GnRHa. Dopamine or PS administered by themselves did not alter plasma concentrations of either stGTH. In Experiment II, sturgeon injected intraperitoneally with a combination of GnRHa and pimozide had significantly higher (p < 0.05) concentrations of plasma stGTH I and stGTH II compared to males receiving GnRHa or pimozide alone. While this effect of GnRHAa + pimozide was observed in the spring, no such potentiation was seen in these fish during the summer (Experiment III). These results represent the first evidence of dopaminergic inhibition of GnRH-induced pituitary gonadotropin secretion in Chondrostean fish.

Induced Spawning, Artificial Fertilization, and Egg Incubation Techniques for Green Sturgeon

“…The sperm concentration in milt of four males ranged from 2.9 3 10 8 to 5.4 3 10 9 sperm/mL and was within the range reported for Eurasian and North American sturgeons (Dettlaff et al 1993;Cosson et al 2000;Park and Chapman 2005). Domperidone was used in this study to enhance pituitary response to GnRHa injections, based on the reported dopaminergic inhibition of gonadotropin release in sturgeon (Pavlick and Moberg 1997) and application of dopamine antagonists for induced spawning of other fishes (Peter et al 1988;Dufour et al 2005). With a limited annual supply of broodfish (two pairs), there was a concern that capture and handling stress would affect GnRH-induced ovulation and therefore the annual production of green sturgeon juveniles needed for research projects.…”

Neuroendocrine control by dopamine of teleost reproduction

“…Interestingly, a dopaminergic inhibition of GnRH‐induced pituitary gonadotropin secretion has also been found in a chondrostean fish, the white sturgeon Acipenser transmontanus Richardson (Pavlick & Moberg, 1997). This indicates that the role of DA in the inhibitory control of reproduction may not be specific to teleosts, but may have a more ancient evolutionary origin, in an actinopterygian ancestor, common to teleostean and chondrostean fishes.…”

Application of dopaminergic antagonist: Metoclopramide, in reproduction of crucian carp Carassius carassius (L.) under controlled conditions

“…In teleost, the stimulatory function of GnRH may be inhibited by dopamine though activation of the dopamine D2 receptor and down regulation of GnRH activity by increase in the GnRH-binding capacity whereas treatment with apomorphin, reversed this effect (De Leeuw et al, 1989). The inhibitory role of dopamine was also confirmed in other fish species such as the common carp Cyprinus carpio L., (Peng et al, 1994), African catfish Clarias gariepinus (Burchell, 1822) (De Leeuw et al, 1988), rainbow trout Oncorhynchus mykiss (Walbaum, 1792) (Saligaut et al, 1998) and white sturgeon Acipenser transmontanus (Richardson, 1836) (Pavlic and Moberg, 1997). Dopamine inhibition of GT release was, however, not confirmed in marine species (Copeland and Thomas, 1989).…”