title: Relaxant effect of chloroquine in rat ileum: possible involvement of nitric oxide and BKCa.
abstract: OBJECTIVE
  Bitter perception has a particularly important role in host defence. However, to date, direct effects of bitter compounds on small intestinal motility have not been shown. This study investigated the effects of bitter compounds on the spontaneous contraction of longitudinal smooth muscle strips of rat ileum.
  
  
  METHODS
  Isolated longitudinal smooth muscle strips of rat ileum were used for tension recording in vitro. Immunofluorescence staining was used to identify the localization of TAS2R10 receptors.
  
  
  RESULTS
  The spontaneous contraction of rat ileum was decreased after chloroquine administration. Other bitter compounds, such as quinine, denatonium and saccharin, exhibited similar effects. Chloroquine-induced relaxation was not blocked by tetrodotoxin, but was partially reversed by the nitric oxide synthase inhibitor L-NAME or the large conductance Ca(2+) -activated K(+) (BKCa) channel antagonist iberiotoxin. By surgically removing the small intestinal mucosa or bathing in Ca(2+) -free Krebs solution, the chloroquine-induced relaxation was largely attenuated. The immunofluorescence staining showed that TAS2R10 receptors were expressed in rat ileum.
  
  
  CONCLUSIONS
  The results indicate that bitter receptor agonists induce relaxation of longitudinal smooth muscle strips of rat ileum, which is mediated by nitric oxide and BKCa channels.
authors: Department of Physiology, Shandong University School of Medicine, Jinan, China.
authors: Fangmiao
authors: F
authors: Jing
authors: Ming
authors: M
authors: Liu
authors: Ning
authors: N
authors: Yang
authors: Yinglu
authors: Y
authors: Liu
authors: Xiaoyu
authors: X
authors: Li
authors: Jingxin
authors: J
authors: Li
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002738:Chloroquine / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005769:Gastrointestinal Motility / Q000187:drug effects / Q000502:physiology; D007082:Ileum / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009126:Muscle Relaxation / Q000187:drug effects* / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D004791:Enzyme Inhibitors; C494842:Kcnma1 protein, rat; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D010455:Peptides; D015221:Potassium Channels; D009569:Nitric Oxide; C064719:iberiotoxin; D002738:Chloroquine; D019001:Nitric Oxide Synthase; D002118:Calcium; D019331:NG-Nitroarginine Methyl Ester