Brain gonadotropin releasing hormone3 expression variation during oogenesis and sexual behavior and its effect on pituitary hormonal expression in the blue gourami

To gain a better insight regarding the roles of gonadotropin releasing hormone3 (GnRH3) in the regulation of reproduction in the suborder Labyrinthici, GnRH3 expression was investigated during the reproduction cycle of the male and female blue gourami (Trichogaster trichopterus). The full-length blue gourami brain GnRH3 gene was sequenced (EMBL acc. no. EU107388) and was found to be expressed in both the brain and pituitary of the blue gourami. High mRNA levels were detected only in the brain of females with oocytes in the maturation stage. Correspondingly, significantly greater mRNA levels of GnRH3 were detected in mature males than in immature ones. In primary cultures of dispersed pituitary cells, GnRH3 significantly increased βFSH and βLH subunit mRNA levels in cells from both females and males, whereas GH gene transcription was affected differently by GnRH3 in females, as compared to males. Thus, we propose that GnRH3 can act differentially in the blue gourami females and males. In females, GnRH3 may be involved in the final maturation stage of the oocyte and induces βFSH, βLH and GH gene expression; in males, it is engaged in sexual behavior and spermatogenesis regulation via βFSH and βLH stimulation and dowregulation of GH transcription.