Upregulation of Kiss-1 and Gpr54 Genes Expression in Pituitary of Male Rats Following the Central Administration of Neuropeptide Y

Introduction: The neuropeptide Y (NPY) in the neural circuits of the hypothalamus has a stimulating effect on reproductive activities in mammals. Kisspeptin (KiSS1) is a quintessential neurotransmitter in the reproductive axis which directly stimulates gonadotropin-releasing hormone neurons in the hypothalamus. The distribution of KiSS1 expressing cells in the pituitary was described previously. Despite earlier reports showing the KiSS1 receptor, G-protein coupled receptor 54 (GPR54) expression in the pituitary, the potential physiological roles of kisspeptin at this gland have remained obscure. Accordingly, this study investigated the role of NPY on the relative expression of Kiss1 and Gpr54 genes in the pituitary gland in male Wistar rats. Methods: In general, 20 male Wistar rats weighing 200-250 g in 4 groups (5 in each group) received saline, NPY (2.3 nM), BIBP3226 (NPY receptor antagonist, 7.8 nM), and NPY+ BIBP3226. Then, they received the simultaneous injection of these molecules through the third ventricle of the brain. Finally, the relative mean expressions of Kiss1 and Gpr54 genes in the anterior pituitary were quantitatively analyzed by the real-time polymerase chain reaction. Results: The central injection of NPY increased the relative mean expressions of Kiss1 and Gpr54 genes in the pituitary gland compared to the control group although the injection of BIBP3226 eradicated these effects. However, the gene expression of Gpr54 in the rats receiving NPY coupled with BIBP3226 in hypophysis in comparison to the group receiving only NPY demonstrated a significant reduction (P<0.05). Conclusion: Overall, the central injection of NPY stimulated the gene expression of Kiss1 and Gpr54 in the pituitary gland.