Involvement of cholinergic neurons in the regulation of the ghrelin secretory response to feeding in sheep.
We previously demonstrated that a transient surge in plasma levels of ghrelin occurs just prior to a scheduled meal and that this surge is modified by the feeding regimen. This suggests that the ghrelin secretion is regulated by the autonomic nervous system, especially the cholinergic projections to the stomach. To test this hypothesis, we investigated changes in plasma ghrelin levels at feeding time in rams by administering cholinergic blockers (atropine and hexamethonium) and a cholinergic accelerator (metoclopramide). The average food intake in each group infused with atropine, hexamethonium, metoclopramide, and saline was 150+/-28, 137+/-46, 153+/-50, and 1075+/-25g, respectively. Plasma ghrelin concentrations increased (P<0.05) after i.v. infusion of hexamethonium and gradually decreased (P<0.05) after i.v. infusion of metoclopramide. Plasma ghrelin levels in hexamethonium-treated animals were greater (P<0.05) than those of atropine-treated animals. Plasma ghrelin levels were significantly (P<0.05) higher in sheep given i.v. infusions of atropine or hexamethonium than the levels in normal- or pair-fed sheep infused with saline. Plasma ghrelin levels were similar in metoclopramide-treated, pair-fed, and control animals. These results support the possibility that ghrelin secretion is regulated by cholinergic neurons of the vagus and that cholinergic activity suppresses ghrelin secretion in sheep.
Sugino
Toshihisa
T
High-tech Research Center, School of Veterinary Medicine and Animal Sciences, Kitasato University, Towada-shi, 034-8628, Aomori, Japan. terashim@vmas.kitasato-u.ac.jp
Yamaura
Junji
J
Yamagishi
Masako
M
Kurose
Yohei
Y
Kojima
Masayasu
M
Kangawa
Kenji
K
Hasegawa
Yoshihisa
Y
Terashima
Yoshiaki
Y
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D018678:Cholinergic Agents / Q000494:pharmacology*; D018679:Cholinergic Agonists / Q000494:pharmacology; D018680:Cholinergic Antagonists / Q000494:pharmacology; D004435:Eating / Q000187:drug effects / Q000502:physiology*; D054439:Ghrelin; D018738:Hexamethonium / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008787:Metoclopramide / Q000494:pharmacology; D009474:Neurons / Q000145:classification / Q000502:physiology*; D036361:Peptide Hormones / Q000097:blood* / Q000378:metabolism; D012756:Sheep; D014630:Vagus Nerve / Q000166:cytology / Q000502:physiology*
D018678:Cholinergic Agents; D018679:Cholinergic Agonists; D018680:Cholinergic Antagonists; D054439:Ghrelin; D036361:Peptide Hormones; D018738:Hexamethonium; D001285:Atropine; D008787:Metoclopramide