Object: The purpose of this study was to assess the effect of the water extracts of rhubarb on bladder detrusor muscle and
to examine the possible mechanism of its action. Methods: Bladder detrusor muscle strips from guinea pigs were suspended in organ baths and the isometric force were measured by ink-writing recorders. The response to rhubarb and the effect of hexamethonium,
phentolamine, atropine and verapamil on rhubarb-induced contraction were also assessed. Results: (1) Administration of rhubarb dose-dependently increased resting tension, mean contractile amplitude and frequency in detrusor strips. (2) α-adrenergic receptor antagonist phentolamine, muscarinic cholinergic antagonist atropine and
calcium channel blocker verapamil partly inhibited the contraction responses induced by rhubarb. Conclusion: The results suggest that rhubarb dose-dependently increased contractile tension, mean contractile amplitude and frequency of detrusor strips. The action of increased tension induced by rhubarb can be inhibited by atropine and phentolanine, suggesting that the action may be via M-muscarinic cholinergic receptor and α1-adrenergic receptor. The action of increased mean contractle amplitude induced by rhubarb can be inhibited by verapamil and atropine, suggesting that the action may be via L-type calcium channel and M-muscarinic cholinergic receptor.