Modulation by protease-activated receptors of the rat duodenal motility in vitro: possible mechanisms underlying the evoked contraction and relaxation

Br J Pharmacol. 1999 Oct;128(4):865-72. doi: 10.1038/sj.bjp.0702755.


1 The present study examined effects of agonist enzymes and receptor-activating peptides for protease-activated receptors (PARs) on duodenal motility in the rat, and also investigated possible mechanisms underlying the evoked responses. 2 Thrombin at 0.03-0.1 microM and the PAR-1-activating peptide SFLLR-NH2 at 3-100 microM or TFLLR-NH2 at 10-50 microM produced a dual action, relaxation followed by contraction of the duodenal longitudinal muscle. The PAR-2-activating peptide SLIGRL-NH2 at 10-100 microM elicited only small contraction. Trypsin at 0.08 microM induced small contraction, or relaxation followed by contraction, depending on preparations. The PAR-4-activating peptide GYPGKF-NH2 at 1000 microM exhibited no effect. 3 The contractile responses of the duodenal strips to TFLLR-NH2 and to SLIGRL-NH2 were partially attenuated by the L-type calcium channel blocker nifedipine (1 microM), the protein kinase C inhibitor GF109203X (1 microM) and the tyrosine kinase inhibitor genistein (15 microM), but were resistant to indomethacin (3 microM) and tetrodotoxin (1-10 microM). 4 The relaxation of the preparations exerted by TFLLR-NH2 was unaffected by indomethacin (3 microM), propranolol (5 microM), NG-nitro-L-arginine methyl ester (100 microM) and tetrodotoxin (1-10 microM). This relaxation was resistant to either GF109203X (1 microM) or genistein (15 microM), but was, remarkably, attenuated by combined application of these two kinase inhibitors. 5 Apamin (0.1 microM), an inhibitor of calcium-activated, small-conductance potassium channels, but not charybdotoxin (0.1 microM), completely abolished the PAR-1-mediated duodenal relaxation, and significantly enhanced the PAR-1-mediated contraction. 6 These findings demonstrate that PAR-1 plays a dual role, suppression and facilitation of smooth muscle motility in the rat duodenum, while PAR-2 plays a minor excitatory role in the muscle, and that PAR-4 is not involved in the duodenal tension modulation. The results also suggest that the contractile responses to PAR-1 and PAR-2 activation are mediated, in part, by activation of L-type calcium channels, protein kinase C and tyrosine kinase, and that the relaxation response to PAR-1 activation occurs via activation of apamin-sensitive, but charybdotoxin-insensitive, potassium channels, in which both protein kinase C and tyrosine kinase might be involved synergistically.

MeSH terms

  • Animals
  • Calcium Channel Blockers / pharmacology
  • Calcium Channels, L-Type / drug effects
  • Duodenum / drug effects
  • Duodenum / physiology*
  • Enzyme Inhibitors / pharmacology
  • Gastrointestinal Motility / drug effects
  • Gastrointestinal Motility / physiology*
  • In Vitro Techniques
  • Male
  • Muscle Contraction / physiology
  • Muscle Relaxation / physiology
  • NG-Nitroarginine Methyl Ester / pharmacology
  • Oligopeptides / pharmacology
  • Propranolol / pharmacology
  • Rats
  • Rats, Wistar
  • Receptors, Thrombin / physiology*
  • Tetrodotoxin / pharmacology
  • Thrombin / pharmacology
  • Trypsin / pharmacology


  • Calcium Channel Blockers
  • Calcium Channels, L-Type
  • Enzyme Inhibitors
  • Oligopeptides
  • Receptors, Thrombin
  • Tetrodotoxin
  • Propranolol
  • Trypsin
  • Thrombin
  • NG-Nitroarginine Methyl Ester