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Regulation of Gonadotropin-Releasing Hormone (GnRH)-Receptor Gene Expression in Tilapia: Effect of GnRH and Dopamine

Levavi-Sivan, B. and Safarian, H. and Rosenfeld, H. and Elizur, A. and Avitan, A. (2004) Regulation of Gonadotropin-Releasing Hormone (GnRH)-Receptor Gene Expression in Tilapia: Effect of GnRH and Dopamine. Biology of Reproduction, 70 (6). pp. 1545-1551.

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Article Link(s): http://dx.doi.org/10.1095/biolreprod.103.021998

Publisher URL: http://www.biolreprod.org/

Abstract

The present work was designed to study certain aspects of the endocrine regulation of gonadotropin-releasing hormone receptor (GnRH-R) in the pituitary of the teleost fish tilapia. A GnRH-R was cloned from the pituitary of hybrid tilapia (taGnRH-R) and was identified as a typical seven-transmembrane receptor. Northern blot analysis revealed a single GnRH-R transcript in the pituitary of approximately 2.3 kilobases. The taGnRH-R mRNA levels were significantly higher in females than in males. Injection of the salmon GnRH analog (sGnRHa; 5–50 μg/kg) increased the steady-state levels of taGnRH-R mRNA, with the highest response recorded at 25 μg/kg and at 36 h. At the higher dose of sGnRHa (50 μg/kg), taGnRH-R transcript appeared to be down-regulated. Exposure of tilapia pituitary cells in culture to graded doses (0.1–100 nM) of seabream (sbGnRH = GnRH I), chicken II (cGnRH II), or salmon GnRH (sGnRH = GnRH III) resulted in a significant increase in taGnRH-R mRNA levels. The highest levels of both LH release and taGnRH-R mRNA levels were recorded after exposure to cGnRH II and the lowest after exposure to sbGnRH. The dopamine-agonist quinpirole suppressed LH release and mRNA levels of taGnRH-R, indicating an inhibitory effect on GnRH-R synthesis. Collectively, these data provide evidence that GnRH in tilapia can up- regulate, whereas dopamine down-regulates, taGnRH-R mRNA levels.

Item Type:Article
Additional Information:© 2004 by the Society for the Study of Reproduction, Inc.
Keywords:dopamine, gonadotropin-releasing hormone, gonadotropin-releasing hormone receptor, pituitary
Subjects:Aquaculture and Fisheries > Aquaculture > Mariculture
Aquaculture and Fisheries > Aquaculture > Fish culture
Science > Biology > Reproduction
Deposited On:09 Jul 2004
Last Modified:15 Jun 2011 23:38

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