ROLE OF TRANSIENT RECEPTOR POTENTIAL A1 (TRPA1) IN COLD-INDUCED CONTRACTION IN THE ISOLATED INTESTINAL STRIPS IN RABBITS

Abstract

Background: Transient receptor potential (TRP) A1, a member of TRP channel family, is
activated by noxious cold. Aim of the work: The present study is designed to determine if
TRPA1 contributed to cold-induced contractions in the isolated rabbit intestinal preparations
and explore the potential mechanisms. Method: The small intestinal smooth muscle layers
were surgically isolated from male rabbits and changes in isotonic tension of longitudinal
muscle under various treatments were recorded as intestinal motilities. Cold stimuli were
obtained by the reperfusion with Tyrode's solution at given temperature. Results: The
contractions induced by cold stimuli (from 37 °C to 12 °C stepwise) were inversely
proportional to the temperature with a maximum contraction at 17 °C in rabbit small intestinal
preparations (P<0.001). Cold-induced intestinal contractions were specially inhibited by
TRPA1 blocker, ruthenium red (30 μmol/ml bath fluid), (P<0.001). The cold-induced
contractions of the small intestinal strips were almost inhibited by the pretreatments of the
strips with TRPA1, Allyl isothiocyanate (AITC, 300 μmol/ml bath fluid) (P<0.01).
Pretreatment of the strips with atropine 10-4M⁄ml bath fluid did not affect the cold induced
contractions in rabbit small intestinal strips (P>0.05). Lidocaine, Na+ channel blocker, (10-2)
M/ml bath fluid reduced the cold induced contraction in the rabbit small intestinal strips
(P<0.05). Conclusions: TRPA1 was involved in cold-induced contractions in the rabbit small
intestinal smooth muscle. Neural mechanism might be involved in that response. Further
studies should be done to clarify role of Ca2+ in cold induced contraction.
Keywords: TRPA1, smooth muscle contraction, cold