Intraventricular ghrelin activates oxytocin neurons: implications in feeding behavior

Abstract

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.

Systemic administration of oxytocin reduces basal and lipopolysaccharide-induced ghrelin levels in healthy men

“…Ghrelin increases the c-fos immunoreactivity of OXT neurons, which are hypothesized to mediate some of the central effects of ghrelin (Olszewski et al 2007). OXT infusion decreases the NPY changes in response to ghrelin in men (Coiro et al 2008).…”

“…A recent study has showed that intraventricular administration of ghrelin increases the c-fos activity of oxytocin (OXT)-secreting neurons (Olszewski et al 2007). OXT is involved in social bonding, has important reproductive functions, and is a classical stress hormone (Gimpl & Fahrenholz 2001, Landgraf & Neumann 2004.…”

Ghrelin in the CNS: From hunger to a rewarding and memorable meal?

“…However, it should be noted that the evidence for longer-term effects is weaker. In the majority of studies, single injections of ghrelin typically have not produced increases in food intake longer than a few hours (e.g., see (Gaskin et al, 2003;Gilg and Lutz, 2006;Kalra et al, 2005;Olszewski et al, 2007b;Olszewski et al, 2003a;Olszewski et al, 2003b;Shrestha et al, 2004;Shrestha et al, 2006)). …”

“…(Olszewski et al, 2007b;Olszewski et al, 2003a;Olszewski et al, 2003b;Wren et al, 2001;Wren et al, 2000)). The orexigenic action persists regardless of the energy status of the organism, i.e., in both deprivation and overfeeding paradigms.…”

“…The majority of standardized laboratory chow diets used in a number of ghrelin studies were carbohydratebased (e.g. (Olszewski et al, 2007b;Olszewski et al, 2003a;Olszewski et al, 2003b;Wren et al, 2001;Wren et al, 2000)). In addition, Bomberg et al found that when calorie-dense yet "bland" chow and an "attractive" calorie-dilute sucrose solution are offered concurrently to ICV ghrelin-treated rats, these animals increase the intake of both ingestants.…”