en Endocrine Physiology/Pharmacology Endocrine Physiology/Pharmacology Experimental research article Experimental research article <p dir="ltr" style="text-align: justify;"><span style="font-size: 12px;"><b>Introduction: </b><font face="Arial,Arial"><font face="Arial,Arial">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. </font></font></span><span style="font-size: 12px;"><b>Methods: </b><font face="Arial,Arial"><font face="Arial,Arial">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. </font></font></span><span style="font-size: 12px;"><b>Results: </b><font face="Arial,Arial"><font face="Arial,Arial">Kisspeptin or NPY injection significantly increased the mean serum testosterone concentration compared to saline at 30 and 60 min postinjection (</font></font><i><font face="Arial,Arial"><font face="Arial,Arial">P</font></font></i><font face="Arial,Arial"><font face="Arial,Arial"><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 (</font></font><i><font face="Arial,Arial"><font face="Arial,Arial">P</font></font></i><font face="Arial,Arial"><font face="Arial,Arial"><0.001). This study indicates that P234 or BIBP3226 significantly attenuated (</font></font><i><font face="Arial,Arial"><font face="Arial,Arial">P</font></font></i><font face="Arial,Arial"><font face="Arial,Arial"><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. </font></font></span><span style="font-size: 12px;"><b>Conclusion: </b><font face="Arial,Arial"><font face="Arial,Arial">Based upon the results, NPY may modulate the testosterone secretion indirectly via the kisspeptin signaling system.</font></font></span></p> Neuropeptide Y, Kisspeptin, HPG axis, Testosterone, Rat 267 276 http://ppj.phypha.ir/browse.php?a_code=A-10-943-1&slc_lang=en&sid=1 Vahid Azizi V_Azizi@sbu.ac.ir 3200319475328460016934 3200319475328460016934 No Department of Animal Biology, Faculty of Biological Sciences, Kharazmi University, Tehran, Iran Shahrbanoo Oryan Sh_Oryan@yahoo.com 3200319475328460016935 3200319475328460016935 Yes Department of Animal Biology, Faculty of Biological Sciences, Kharazmi University, Tehran, Iran Homayoun Khazali H_Khazali@sbu.ac.ir 3200319475328460016936 3200319475328460016936 No Department of Physiology, Faculty of Biological Sciences, Shahid Beheshti University, Tehran, Iran Abdolkarim Hosseini ab_hosseini@sbu.ac.ir 3200319475328460016937 3200319475328460016937 No Department of Physiology, Faculty of Biological Sciences, Shahid Beheshti University, Tehran, Iran