Central actions of the nonpeptide growth hormone secretagogue GHS-25

Growth hormone secretagogues (GHSs) increase the activity of hypothalamic a rcuate nucleus neurons thought to be involved in controlling the release of growth hormone (GH). The GHS receptor is also found in hypothalamic region s not associated with the release of CH, suggesting that GHSs may influence other hypothalamic systems. This study utilized double-labeling immunocyto chemical techniques to examine the hypothalamic actions of a novel nonpepti de CHS, GHS-25, In common with other GHSs, GHS-25 induced significant amoun ts of Fos immunoreactivity in the arcuate nucleus of conscious male rats. H owever, unlike other CHSs, GHS-25 also induced Fos immunoreactivity in the supraoptic nucleus. Double labeling revealed that approx 66% of supraoptic nucleus cells that were Fos positive after the administration of GHS-25 wer e also immunoreactive for oxytocin, Thus, in addition to its actions on the GH axis, GHS-25 may influence the release of neurohypophyseal hormone.