Gonadotropin-releasing hormone (GnRH) neurons are the final target of a complex network regulating reproduction. The balance between excitatory and inhibitory inputs is essential for rhythmic GnRH secretion, including pulses and surges, yet the underlying mechanisms remain unresolved. Here, using adult animals of both sexes, we test the hypothesis that excitatory kisspeptin and inhibitory neuronal nitric oxide (NO) synthase (nNOS)-derived inputs orchestrate GnRH release within a microcircuit of kisspeptin, nNOS and GnRH neurons (the "KiNG" network). We focus on nNOS neurons of the organum vasculosum of the lamina terminalis (OV) and the median preoptic nucleus (MePO), which interact with kisspeptin and exhibit cycle-dependent kisspeptin receptor (Kiss1r) expression. Using a highly-sensitive NO/cGMP biosensor together with electrophysiological, genetic, chemogenetic and pharmacological approaches we demonstrate that kisspeptin induces NO-dependent cGMP production in the OV/MePO, including in GnRH neurons, which in turn fine-tunes the GnRH/LH response, providing mechanistic insights into how the KiNG network shapes pulse and surge generation.
Delli et al. (Tue,) studied this question.