Ghrelin participates in the two-way regulation of the motility of the small intestinal smooth muscle in rats

Abstract

Objective To investigate the effect and mechanism of Ghrelin on the contraction and relaxation of rat small intestinal smooth muscle. Methods The effect of different concentrations of Ghrelin (0;20;40;80 μg/kg) on the small intestinal transit in vagotomized rats in vivo and Ghrelin (0.01; 0.1;0.5 ; 1.0 μmol/L) on the contraction and relaxation of rat small intestinal smooth muscle strips in vitro was observed,the locations of Ghrelin receptors (GHS-R1 a) in small intestinal muscle layers were detected by immunofluorescency. Results Ghrelin dose-dependently increases small intestinal transit (( 25.4 ± 1.0)％,(33.7 ± 1.9)％,(39.3 ±2.4)％,(44.7 ±2.1)％),enhances the contraction ((67.0 ±2.4)％,(149.5 ±3.3)％,(187.1 ±4.7)％,(213.5 ±3.4)％) and relaxation ((35.3 ± 1.1)％,(62.9 ± 3.8 ) ％,( 79.6 ± 2.7 ) ％,( 94.6 ± 2.2 ) ％ ) of smooth muscle strips mediated by carbachol.Ghrelin receptors were mainly located on membrane of the nerve cells in the muscle layers,while no receptors exist on membrane of smooth muscle cells. Conclusions Ghrelin enhances the effect of contraction and relaxation of rat small intestinal smooth muscle mediated by cholinergic neurotransmitters activating nerve cells in the enteric plexus. Key words: Animal experimentation; Receptors,Ghrelin; Myenteric plexus