[Effect and mechanism of ghrelin and its synthetic peptide growth hormone releasing peptide 6 on gastric motor in mice].
OBJECTIVE
To investigate the effect and mechanism of ghrelin and its synthetic peptide GHRP-6 on gastric motor in mice.


METHODS
In vivo, the dose-dependent effects of ghrelin (20,50,100,200 mug/kg) and GHRP-6 (20,50,100,200 mug/kg) on gastric emptying were measured by intragastric application of phenol red test which was adapted for use in mice. The effects of atropine, NG-nitro-L-arginine methyl ester (L-NAME), and D-Lys(3)-GHRP-6 (GHS-R antagonist) on the gastric motor induced by ghrelin and GHRP-6 (100 mug/kg) were also investigated. In vitro, the effects of ghrelin (0.01,0.1,1.0,10.0 mumol/L) and GHRP-6 (0.01,0.1,1.0,10.0 mumol/L) on spontaneous contraction of mice fundic muscle strips were studied as well.


RESULTS
Both ghrelin (50,100,200 mug/kg) and GHRP-6 (50,100,200 mug/kg) significantly accelerated gastric emptying (P<0.05), but they failed to accelerate gastric emptying in the presence of atropine, L-NAME and D-Lys(3)-GHRP-6 (P<0.05). Ghrelin (0.1, 1.0, 10.0 mumol/L) and GHRP-6 (0.1, 1.0, 10.0 mumol/L) induced significant contraction of fundic muscle strips in concentration-dependent manner (P<0.05), which could be blocked by tetrodotoxin.


CONCLUSIONS
Ghrelin and its synthetic peptide GHRP-6 accelerate gastric emptying perhaps by activating GHS-R of cholinergic excitatory pathways and nitrergic nervous pathways in the enteric nervous system.
Qiu
Wen-Cai
WC
Department of General Surgery, The 6th People's Hospital of Shanghai, School of Medicine, Shanghai Jiaotong University, Shanghai 200233, China.
Wang
Zhi-Gang
ZG
Wang
Wei-Gang
WG
Zheng
Qi
Q
D000818:Animals; D005260:Female; D005746:Gastric Emptying / Q000187:drug effects*; D054439:Ghrelin / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009842:Oligopeptides / Q000494:pharmacology*; D013270:Stomach / Q000187:drug effects / Q000502:physiology*
C520836:GHRP-6, Lys(3)-; D054439:Ghrelin; D009842:Oligopeptides