Objective  To investigate the number and distribution of interstitial cells of Cajal(ICCs) in unstable bladder

and their changes on the contraction of muscle strip of unstable detrusor.   Methods  Detrusor instability model was established by partial bladder outlet obstruction. About a 3 mm×4 mm detrusor strip was harvested from normal and unstable bladder. The c-kit positive cells were detected by immunofluorescence. About a 2 mm×7 mm detrusor strip was used to assess the frequency and the amplitude of strip contraction. The effect of c-kit blocker Glevic on unstable strip contraction was evaluated.   Results  The number of ICCs (c-kit positive cells) increased significantly in unstable bladder than that in stable bladder（P0.05). ICCs were mostly scattered in normal bladder

but in network distribution in unstable bladder. The contraction amplitude and frequency of unstable strips was significantly higher than that of normal strips. When exposed to Glevic

the contraction amplitude of unstable strips reduced significantly with no influence on contraction frequency.   Conclusion  The number of ICCs increased significantly and interacted tightly in unstable bladder. The contraction amplitude and frequency of unstable strips is significantly higher than that of normal strips and can be significantly the contraction amplitude can be reduced by Glevic

which might indicate a close relationship between the ICCs and the detrusor instability.