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Transient receptor potential A1 is involved in cold-induced contraction in the isolated rat colon smooth muscle

DONG Yang, SHIHai-Lian, SHI Jian-Rong, WU Da-Zheng

Institute of Chinese Materia Medica, Shanghai Key Laboratory of Complex Prescription； Experimental Teaching Centre, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China

Abstract

Transient receptor potential (TRP) A1, a member of TRP channel family, is activated by noxious cold. The aims of this studywere to determine if TRPA1 contributed to cold-induced contractions in the isolated rat colon preparations and explore the potentialmechanisms. The colon smooth muscle layers were surgically isolated from the male Wistar rats and changes in isotonic tension oflongitudinal muscle under various treatments were recorded as colonic motilities. Cold stimuli were obtained by the reperfusion withKrebs-Henseleit solution at given temperature using Constant Flow Pump. The mRNA expressions of TRPA1, TRPV1 and TRPM8in rat colon smooth muscle layer were examined by using reverse transcription-polymerase chain reaction (RT-PCR) techniques. Theresults showed that the contractions induced by cold stimuli (from 37 °C to 12 °C stepwise) were inversely proportional to thetemperature with a maximum contraction at 17 °C in both proximal and distal colons (P<0.01). RT-PCR analysis revealed theexpression of TRPA1, but not TRPM8 and TRPV1, in the rat proximal and distal colon smooth muscle layers. Cold-induced coloniccontractions were specially inhibited by TRPA1 blocker, ruthenium red (30 μmol/L), in the proximal and distal colon (P<0.05). Thecold-induced contractions of proximal (P<0.01, P<0.05) and distal colons (both P<0.001) were almost abolished or inhibited by thepretreatments of TRPA1 agonists, Allyl isothiocyanate (AITC, 300 μmol/L) and cinnamaldehyde (CA, 1 mmol/L). Extracellularcalcium removal (EGTA, 1 mmol/L), PLC blocker (U73122, 10 μmol/L) and IP3 receptor blocker (2-aminoethoxydiphenyl borate,2-APB, 30 μmol/L) all decreased the contractions evoked by the cooling at 17 °C in the proximal and distal colon (P<0.001, P<0.05,P<0.001). Atropine (1 μmol/L) had no effects on these contractions. L-type Ca2+ channels blocker nifedipine (1 μmol/L) and neurotoxintetrodotoxin (TTX, 2 μmol/L) decreased the contractile response in the distal colon (P<0.01, P<0.05), but not in the proximal colon.In conclusion, TRPA1 contributes to cold-induced contractions of the rat colon smooth muscle, and the mechanism of TRPA1activation involves PLC/IP3/Ca2+ pathway. L-type Ca2+ channel and neurogenic mechanism other than muscarinic receptor might bepartially involved in cold-induced contraction of the distal colon, which probably resulted in higher contraction of distal coloncompared with that of proximal colon.

Key words: Colon; smooth muscle; contraction; TRPA1

Received: 2010-05-11　　Accepted: 2010-06-24

Corresponding author: 吴大正　　E-mail: wdazheng@hotmail.com

Citing This Article：

DONG Yang, SHIHai-Lian, SHI Jian-Rong, WU Da-Zheng. Transient receptor potential A1 is involved in cold-induced contraction in the isolated rat colon smooth muscle. Acta Physiol Sin 2010; 62 (4): 349-356 (in Chinese with English abstract).