The neuroendocrine regulation of pulsatile growth hormone (GH) secretion involves the reciprocal interactions between growth hormone-releasing hormone (GHRH)- and somatostatin-containing neurones, residing primarily in the hypothalamic arcuate nucleus (ARC) and the periventricular nucleus (PeN), respectively. Considerable evidence supports the concept that GH itself participates in the regulation of its own rhythmic secretion through a reciprocal feedback on GHRH and somatostatin neurones. The direct actions of GH are mediated through GH receptors, and in the PeN, the majority of somatostatin neurones express this receptor. GH induces the expression of the immediate early gene c-fos in the ARC; however, few GHRH residing in the ARC express the GH receptor, suggesting that the action of GH on GHRH cells must be indirect through another population of unidentified cells. NPY neurones express c-fos in response to GH, and preliminary results suggest that NPY neurones in the ARC express the GH receptor. These observations suggest that NPY neurones play a physiological role in the feedback of regulation of GH secretion.