Figure 14.

Schematic working model of multiple signals involved in surge generation. The gray dotted box indicates portion of sagittal brain sketch magnified in schematic figure. For simplicity only, the substances with the most evidence for involvement in surge regulation are depicted; see text for full description of each neuromodulator. Excitatory inputs (green lines and text) arise from the AVPV, SCN, and medulla, mediated by kisspeptin (kiss), GABA, VIP, and catecholamines. Inhibitory inputs (red text) arising from the arcuate nucleus (ARC) and dorsomedial hypothalamus (DMH) mediated by endogenous opioid peptides (EOPs), NKB, and GnIH/RFRP-3 are reduced (dashed red line) during the surge. The SCN provides excitatory input to the AVPV and inhibitory input to the DMH at appropriate times of day to coordinate changes in downstream inputs to GnRH neurons. Sagittal brain sketch courtesy of Dr. Paul Heideman. (The College of William and Mary, Williamsburg, Virginia).