Kisspeptin, neurokinin B, and dynorphin act in the arcuate nucleus to control activity of the GnRH pulse generator in ewes.

Recent work has led to the hypothesis that kisspeptin/neurokinin B/dynorphin (KNDy) neurons in the arcuate nucleus play a key role in GnRH pulse generation, with kisspeptin driving GnRH release and neurokinin B (NKB) and dynorphin acting as start and stop signals, respectively. In this study, we tested this hypothesis by determining the actions, if any, of four neurotransmitters found in KNDy neurons (kisspeptin, NKB, dynorphin, and glutamate) on episodic LH secretion using local administration of agonists and antagonists to receptors for these transmitters in ovariectomized ewes. We also obtained evidence that GnRH-containing afferents contact KNDy neurons, so we tested the role of two components of these afferents: GnRH and orphanin-FQ.

KNDy (kisspeptin/neurokinin B/dynorphin) neurons are activated during both pulsatile and surge secretion of LH in the ewe.

KNDy (kisspeptin/neurokinin B/dynorphin) neurons of the arcuate nucleus (ARC) appear to mediate the negative feedback actions of estradiol and are thought to be key regulators of pulsatile LH secretion. In the ewe, KNDy neurons may also be involved with the positive feedback actions of estradiol (E(2)) to induce the LH surge, but the role of kisspeptin neurons in the preoptic area (POA) remains unclear. The goal of this study was to identify which population(s) of kisspeptin neurons is (are) activated during the LH surge and in response to the removal of E(2)-negative feedback, using Fos as an index of neuronal activation.