Figure 3.

Interactive model postulated to account for rapid SS, GHRH, and GH pulses within a volley driven by a primary arcuate-nucleus (ArC) oscillator (top). Resultant multipulse volleys of GH are quenched by GH’s autofeedback on the periventricular nucleus (PeV), thus creating a secondary slower oscillator (bottom right). The GH-releasing peptide, ghrelin, amplifies the size of GH pulses by opposing the inhibitory actions of SS on GHRH pulses within ArC and on GH release by somatotropes in the pituitary gland. [Adapted with permission from L. S. Farhy et al.: Am J Physiol Regul Integr Comp Physiol 292:R1577–R1593, 2007 (18).]