Arecoline excites the contraction of distal colonic smooth muscle strips in rats via the M 3 receptor – extracellular Ca 2+ influx – Ca 2+ store release pathway

• Published in: Canadian journal of physiology and pharmacology 2010-04, Vol.88 (4), p.439-447
• Main Authors: Li, Chuan-Bao, Yang, Xiao, Tang, Wen-Bo, Liu, Chuan-Yong, Xie, Dong-Ping
• Format: Article
• Language: English
• ISSN: 0008-4212; 1205-7541
• DOI: 10.1139/Y10-024

Areca is a Chinese herbal medicine that is widely used for constipation. However the mechanisms of its action are not clear. We investigated the effects of arecoline, the most active component of areca, on the motility of rat distal colonic smooth muscle strips. In longitudinal muscle of distal colon (LMDC) and circular muscle of distal colon (CMDC), arecoline increased the contraction in a dose-dependent manner. Tetrodotoxin (TTX) did not inhibit the effects of arecoline. The contractile response to arecoline was completely antagonized by atropine. 4-Diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP) strongly depressed the response to arecoline, but gallamine and methoctramine did not. Nifedipine, 2-aminoethoxydiphenyl borate (2-APB), and Ca 2+ -free Krebs solution with EGTA partly inhibited the effects of arecoline. The sum of Ca 2+ -free Krebs solution, EGTA, and 2-APB completely inhibited the effects of arecoline. The results show that arecoline stimulates distal colonic contraction in rats via the muscarinic (M 3 ) receptor – extracellular Ca 2+ influx – Ca 2+ store release pathway. It is likely that the action of areca in relieving constipation is due to its stimulation of muscle contraction.