Simultaneous Effect of Kisspeptin and Galanin on Serum Luteinizing Hormone and Testosterone Levels in Male Rats

Abstract

Background: Galanin is a neuropeptide with a wide range of physiological functions that also has stimulatory effects on the reproductive axis. Kisspeptin is a crucial neuropeptide for the stimulation of the reproductive function. In the present study, the interaction of kisspeptin and the galanin signaling system was investigated on the mean serum luteinizing hormone (LH) and the testosterone concentrations in rats. Materials and Methods: Fifty-five male Wistar rats in 11 groups (n=5 per group) received saline, kisspeptin (1nmol), P234(1nmol), galanin(1nmol), galantide (1nmol) or simultaneous injections of them via third cerebral ventricle at 07:00 - 07:30. Blood samples were collected at 30 min following the injections. Hormone concentrations were measured using rat kit and the method of the radio-immunoassay (RIA). Results: Kisspeptin or galanin injection significantly increased both the mean serum LH and the testosterone concentration compared to saline (P<0.05). The co-administration of kisspeptin/galanin increased the mean serum LH and the testosterone concentration significantly compared to galanin or saline (P<0.05). The co-administration of kisspeptin/galanin decreased the mean serum LH concentration compared to kisspeptin, this reduction, however, was not statistically significant. Also, testosterone concentration declined in the kisspeptin/galanin group compared to kisspeptin group. Galantide or p234 injection decreases the mean serum LH and the testosterone concentration compared to galanin and kisspeptin, respectively. The co-administration of galantide/p234 lowers the mean serum LH concentration compared to saline. Conclusion: The interaction of hypothalamic galanin and kisspeptin signaling pathways may play an important role in the modulation of hormonal control of the hypothalamus-pituitary-gonadal axis. [GMJ. 2017;6(1):23-29]