Intraventricular ghrelin activates oxytocin neurons: implications in feeding behavior.

Ghrelin affects behavioral and physiological responses, such as feeding or the activity of the HPA axis. Distribution of its receptor in central sites involved in neuroendocrine control, including the hypothalamic paraventricular nucleus, indicates that interplay with multiple neuropeptidergic systems underlies ghrelin's actions. We report that intracerebroventricular ghrelin increases c-Fos immunoreactivity of oxytocin neurons in magno and parvocellular portions of the paraventricular nucleus. The orexigenic response to ghrelin administered at the dose that activates oxytocin neurons can be further elevated by pretreatment with a selective oxytocin receptor antagonist. Our data suggest that oxytocin may be responsible for the mediation of some effects induced by ghrelin. Modifications in the activity of the oxytocin system may alter some of these effects.