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Japanese researchers have unveiled groundbreaking insights into how specific neurons in the brain influence the release of crucial hormones that govern ovarian functions in females, including follicular development and ovulation. Their findings, recently published in Scientific Reports, offer a potential avenue for comprehending and addressing reproductive disorders in both animals and humans.
The study delves into the role of kisspeptin neurons in the brain, which regulate the release of hypothalamic gonadotropin-releasing hormone (GnRH) and pituitary follicle-stimulating hormone/luteinizing hormone (LH). This intricate process holds significant importance in reproductive functions across mammals, including humans, as it stimulates ovaries for crucial reproductive processes like follicular development and ovulation.
The research primarily focused on two brain areas involved in this process: the arcuate nucleus (ARC) and the anteroventral periventricular nucleus (AVPV). Kisspeptin neurons in these areas play distinctive roles in controlling the secretion of hormones vital for reproduction. Notably, kisspeptin neurons in the ARC produce and respond to dynorphin, an inhibitory substance, while those in the AVPV trigger hormone surges leading to ovulation.
Mayuko Nagae, a postdoctoral fellow, and Yoshihisa Uenoyama, an associate professor at Nagoya University in Japan, emphasized the significance of kisspeptin neurons expressing dynorphin and their role in fertility. They aimed to understand the precise function of dynorphin and its receptor in regulating kisspeptin neurons’ activity.
The researchers genetically modified female rats, targeting the deletion of Kiss1—a gene coding for kisspeptin—in neurons expressing the dynorphin receptor. Their findings revealed altered kisspeptin neuron levels in both ARC and AVPV regions, resulting in prolonged estrous cycles, reduced ovarian weight, and fewer offspring in the modified rats, despite their fertility remaining intact.
Professor Hiroko Tsukamura from Nagoya University highlighted the study’s groundbreaking nature, noting its elucidation of the critical role played by kisspeptin neurons with dynorphin receptors in regulating hormonal secretion and ovulation in female rats. The findings mark the first demonstration of the necessity of kisspeptin neurons receiving direct dynorphin input to regulate GnRH/LH pulses and surges in female rats.
Excited about further studies to uncover molecular mechanisms controlling kisspeptin neuronal activity, Professor Tsukamura underscored the potential applications of these findings in advancing understanding of reproductive mechanisms and addressing ovarian disorders in livestock and human infertility.
