Ovaprim abrogates expression of GnRH receptor- II in the Indian catfish

Abstract

Hormone-induced breeding of fish has been effectively achieved with ovaprim, a salmon GnRH analog, in several teleost fish but not quite successfully in the Indian catfish. In order to analyze the rationale behind ovaprim ineffectiveness in this species, we investigated the effect of ovaprim injection on the GnRH receptors of the ovary and other extra-pituitary organs, since GnRH receptors are known to be over-expressed during spawning. RT-PCR analysis revealed that the GnRH receptor-II is present not only in the ovary, but also in the testis, liver and heart tissues of the catfish. However, the expression of the receptor declined in a time-dependent manner in response to ovaprim injection in all the above tissues. Concomitant changes were observed in the histology of the ovary, which indicated a decrease in the number of the immature ovarian follicles, thus elucidating the rationale behind partial success of ovaprim-induced spawning in the Indian catfish, as compared to other teleosts.