In vivo and in vitro effects of neuropeptide K and neuropeptide gamma on the release of growth hormone

There is anatomical and experimental evidence suggesting that tachykinins have a role in the regulation of secretion of anterior pituitary Hormones. In this investigation, the effects of neuropeptide K and neuropeptide gamma on the secretion of GH were studied in vivo and in vitro. Injections of neuropeptide K into the third ventricle of freely moving, ovariectomized rats resulted in a significant increase of plasma GH, but neuropeptide gamma induced no significant changes in these levels, although it did induce a significant increase in GH pulse height. In vitro, neither neuropeptide K nor neuropeptide gamma had any apparent effect on GH release from hemipituitaries incubated for 2 h. These results suggest that neuropeptide K may have a modulatory function in the regulation of GH secretion from the anterior pituitary, through an action exerted at the hypothalamic level, and the effects of neuropeptide gamma seem to be more marginal.