ABSTRACT
<p><b>OBJECTIVE</b>To observe the influences of quercetin (Que) on the contraction of small intestine smooth muscle of rabbits in vitro and explore the mechanism.</p><p><b>METHODS</b>With the isothermal perfusion of small intestine in vitro. The influences of quercetin on the spontaneous contraction of small intestine and contraction induced by Ach, histamine and Bacl2 were observed and the mechanism of quercetin was studied.</p><p><b>RESULTS</b>Quercetin reduced the tension of contraction of small intestine smooth muscle in rabbits in a dose-depended manner. Quercetin could completely block the contraction of Bay K8644. Heparin could also block the inhibition of quercetin on small intestine smooth muscle but ruthenium red (RR) had no effect on the relaxation of quercetin. Nitro-L-arginine methylester(L-NAME) inhibited the relaxation of quercetin.</p><p><b>CONCLUSION</b>Quercetin inhibits the contraction of small intestine smooth muscle of rabbits in vitro. The mechanism may be related to increase NO concentration in small intestine smooth muscle so that it inhibits extracellular Ca2+ inflowing via cell membrane. And quercetin has effect on intracellular Ca2+ releasing via IP3 of sarcoplasmic reticulum.</p>