Des-acyl Ghrelin Acts by CRF Type 2 Receptors to Disrupt Fasted Stomach Motility in Conscious Rats

Abstract

Although it has been shown that des-acyl ghrelin decreases food intake and gastric emptying, no previous studies have examined the effects of des-acyl ghrelin on physiologic fed and fasted motor activity in the gastrointestinal tract. We examined the effects of intraperitoneal (IP) administration of des-acyl ghrelin on food intake and the effects of intracerebroventricular (ICV) or intravenous (IV) administration of des-acyl ghrelin on gastroduodenal motility using freely moving conscious rat models. The brain nuclei responding to these effects were examined by c- fos immunohistochemistry of the brain sections. IP injection of des-acyl ghrelin decreased food intake, and this effect was not altered by capsaicin treatment. IP injection of des-acyl ghrelin enhanced c- fos expression in the arcuate and paraventricular nucleus but not in the nucleus of the solitary tract. Both ICV and IV injection of des-acyl ghrelin disrupted fasted motor activity in the antrum but not in the duodenum. Changes in gastric motility induced by IV injection of des-acyl ghrelin were completely antagonized by ICV injection of a selective corticotropin-releasing factor (CRF) 2 receptor antagonist; however, the CRF 1 receptor antagonist had no effects. The results suggest that des-acyl ghrelin decreases food intake and disrupts the fasted motor activity of the antrum in freely moving conscious rats. Peripheral des-acyl ghrelin may induce this function by direct activation of brain receptor by crossing the blood-brain barrier but not by the activation of vagal afferent pathways. In the brain, CRF 2 receptor, but not CRF 1 receptor, is involved in this action.