RESUMO
Until 2000 it was believed that gonadotropin-releasing hormone [GnRH] was the sole regulator of hypophyseal gonadotropes. In 2000, the discovery of a gonado-tropin inhibitory hormone [GnlH] initiated a revolution in the field of reproductive physiology. Identification of GnlH homologues in mammals, the arginine-pheny-lalanine-amide [RFamide]-related peptides [RFRPs], indicated a similar function. Subsequently, further works conducted in various laboratories worldwide have shown that these neuropeptides inhibit the hypothalamic-hypophyseal axis. This review discusses the role of RFRPs in mammalian reproductive processes
RESUMO
Kisspeptin and RFamide-related peptide-3 [RFRP-3] are known to affect GnRH/luteinizing hormone [LH] in several species, including the rat. It has been hypothesized that GnRH/LH changes during the rat estrous cycle may result from changes in the expression of KiSS1 and RFRP-3 genes. Therefore, the present study investigates KiSS1 and RFRP-3 gene expression at the transcriptional level in the rat hypothalamus during the estrous cycle. In the present experimental study, 36 adult female Sprague-Dawley rats [3-4 months old] were used to study the expression of KiSS1 and RFRP-3 mRNA in the hypothalamus during the estrous cycle. Four rats were ovariectomized, whereas the remainder were allotted to four different phases of the estrous cycle [n=8 per estrus phase]. Rats were decapitated, and the hypothalami were immediately dissected and frozen in liquid nitrogen. Expressions of KiSS1 and RFRP-3 mRNAs were analyzed by real-time PCR. The expression of KiSS1 mRNA during estrus was lower than other phases of the cycle [p<0.01]. Expression of KiSS1 mRNA during the metestrus phase was lower than the proestrus phase [p<0.01]. The expression of RFRP-3 mRNA during proestrus was lower than the diestrus phase [p<0.01]. Results of the present study showed the role of coordinated expression of KiSS1 and RFRP-3 mRNA in the hypothalamus in the control of the rat estrous cycle