title: [Growth hormone secretagogue participates in two-way regulation of the motility of small intestinal smooth muscle in rats].
abstract: OBJECTIVE
  To investigate the effect of growth hormone secretagogue(ghrelin) on the contraction and relaxation of small intestinal smooth muscle in rats and its mechanism.
  
  
  METHODS
  Twenty-four vagotomized rats were injected intraperitoneally with different concentrations of ghrelin (0, 20, 40, 80 μg/kg). The small intestinal transit were observed. The effect of ghrelin(0.01, 0.1, 0.5, 1.0 μmol/L) on the contraction and relaxation of rat small intestinal smooth muscle strips was observed in vitro in the presence of carbachol(50 nmol/L), the locations of ghrelin receptors(GHS-R1a) on different cells in small intestinal muscle layers were detected by immunofluorescence.
  
  
  RESULTS
  With the increase of concentrations, ghrelin elevated the percentage of small intestinal transit[(25.4±1.0)%, (33.7±1.9)%, (39.3±2.4)%, (44.7±2.1)%] in a dose-dependent manner, and the differences were statistically significant among groups(P<0.05). Ghrelin could also enhance 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 Cch in a dose-dependent manner, and the differences were statistically significant among groups(P<0.05). Immunofluorescence revealed that ghrelin receptors mainly located on membrane of the nerve cells in the muscle layers, while no receptors were observed on membrane of the smooth muscle cells.
  
  
  CONCLUSIONS
  Ghrelin may enhance the effect of the contraction and relaxation of the rat small intestinal smooth muscle mediated by cholinergic neurotransmitters by activating the nerve cells in the enteric plexus.
authors.affiliation: Department of Anesthesiology and Imaging Medicine Center, The First Hospital of Huai'an, Nanjing Medical University, Jiangsu Huai'an 223300, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zheng
authors.forename: Cheng-guang
authors.initials: CG
authors.lastname: Yang
authors.forename: Wen-cai
authors.initials: WC
authors.lastname: Qiu
authors.forename: Xin
authors.initials: X
authors.lastname: Chang
mesh_terms: D000818:Animals; D005769:Gastrointestinal Motility; D054439:Ghrelin / Q000494:pharmacology*; D007421:Intestine, Small / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D054439:Ghrelin