The involvement of kisspeptin in centrally regulatory mechanism of neuropeptide Y on testosterone secretion in male Wistar rats

Introduction: Numerous studies have demonstrated that kisspeptin, a peptide from the KISS1 gene, plays an important role in regulating the secretion of gonadotropin releasing hormone (GnRH). Also, there is some evidence suggesting that kisspeptin can interact with other neuropeptides for the control of the reproductive axis. In the present study, we have investigated the effect of central administration of either kisspeptin or neuropeptide Y (NPY) or both on the mean plasma testosterone concentration in male rats. Methods: In this experimental study, 66 male Wistar rats were allocated into 11 groups (n=6 per group) receiving saline, kisspeptin (1 nmol), P234 (kisspeptin receptor antagonist, 1 nmol), NPY (2.3 nmol), BIBP3226 (NPY receptor antagonist, 7.8 nmol) or co-administration of them via intracerebroventricular (ICV) injection at 9:00-9:30 A.M. Blood samples were collected at 30 and 60 min following the injections for hormone assay. The serum testosterone concentration was measured using rat testosterone kit and the method of radioimmunoassay. Results: Kisspeptin or NPY injection significantly increased the mean serum testosterone concentration compared to saline at 30 and 60 min postinjection (P<0.001). The co-injection of kisspeptin+NPY considerably raised the mean serum testosterone concentration compared to NPY in both 30 and 60 min after the administration (P<0.001). This study indicates that P234 or BIBP3226 significantly attenuated (P<0.001) the testosterone increase after the kisspeptin injection compared to kisspeptin while a stimulatory increase effect was observed in the kisspeptin groups compared to either NPY or kisspeptin. Conclusion: Based upon the results, NPY may modulate the testosterone secretion indirectly via the kisspeptin signaling system.