Central Injection of Substance P Antagonizes the Rf Amide-Related Peptide-3 Impacts on Hypothalamic Kiss-1 and Gnrh Gene Expressions in Male Wistar Rats

Introduction: gonadotropin-inhibitory hormone (gnih) and its mammalian orthologue rf amide-related peptide (rfrp) are known to inhibit the secretion of gonadotropins. in addition, substance p (sp), a member of tachykinin’s family, can increase the firing rate of kisspeptin/neurokinin b/dynorphin (kndy) neurons and provoke the secretion of gonadotropins. in this experimental study, we investigated the effects of co-administration of rfrp-3 and sp on the expression of kiss-1 and gnrh genes, as gonadotropin regulator genes, in male rats. methods: forty-two mature wistar rats were randomly allocated into 7 groups (n=6 in each group). animals in each group intracerebroventricularly received either saline+dmso, sp (1nmol), rfrp-3 (5 nmol), sp (1nmol) + rfrp-3 (5 nmol), sp (1 nmol) + rf9 (rfrp-3 receptor antagonist, 10 nmol), sp (1 nmol) + p234 (kisspeptin receptor antagonist, 1 nmol) + rfrp-3 (5 nmol), or sp (1 nmol) + cp-96,345 (sp receptor antagonist, 5 nmol) + rfrp-3 (5 nmol). two hours after injections, hypothalamic samples were collected to evaluate the expression of target genes by real-time pcr. results: injections in sp and sp + rf9 groups increased the expression of both gnrh and kiss-1 genes (p < 0.05). injections in rfrp-3 and sp + rfrp-3 + cp-96,345 groups significantly decreased the expression of gnrh and kiss-1 genes (p < 0.05). however, injections of sp + rfrp-3 and sp + rfrp-3 + p234 did not significantly change the expression of gnrh and kiss-1 genes. conclusion: the results of our study indicated that sp antagonized the effects of rfrp-3 in the expression of hypothalamic kiss-1 and gnrh genes.