Aim:Our previous study indicated that there are two types of Ca~(2+)release eventsseen in intact mouse bladder tissue.In this study our aim is to investigate themechanism that underlies the phenomena of Ca~(2+)release in smooth muscle.Methods:Single cells were isolated and tissue segments were prepared by cuttingthe detrusor into 0.1 cm×0.5 cm strips running along the axis from the neck to thefundus.Single cells and intact tissue strips were co-loaded with the Ca~(2+)indicatorand caged Ca~(2+)by incubation with 10μmol/L Fluo-4 AM and DMNP-EDTA-AM.Fluo-4 AM fluorescence was detected by laser scanning confocal microscopy,and local uncaging of DMNP-EGTA was achieved by brief exposure to the outputof a diode-pumped,Ti:sapphire laser tuned to 730 nm.Results:Local uncaging ofcaged Ca~(2+)was able to trigger Ca~(2+)release events in both single cells and tissuestrips from mouse bladder.The Ca~(2+)release events could not be blocked byryanodine alone,but the property of the Ca~(2+)release was markedly altered.Surprisingly,in the presence of ryanodine,Xestospongin C completely inhibitedthe Ca~(2+)release events both in single cell and tissue experiments.Conclusion:(1)Two photon flash photolysis(TPFP)triggers Ca~(2+)induced Ca~(2+)release.Thisprocess involves release through type 2 ryanodine receptor channels;(2)TPFPresults in the release of Ca~(2+)through inositol 1,4,5-trisphosphate receptors in theabsence of phospholipase C activation. Aim: Our previous study indicated that there are two types of Ca ~ (2+) release eventsseen in intact mouse bladder tissue. In this study our aim is to investigate themechanism that underlies the phenomena of Ca ~ (2+) release in smooth muscle . Single Cells were isolated and tissue segments were prepared by cutting the detrusor into 0.1 cm × 0.5 cm strips running along the axis from the neck to the fundus. Single cells and intact tissue strips were co-loaded with the Ca ~ (2+) Indatorand caged Ca 2+ was incubated by 10 μmol / L Fluo-4 AM and DMNP-EDTA-AM. Fluo-4 AM fluorescence was detected by laser scanning confocal microscopy, and local uncaging of DMNP-EGTA was achieved by brief exposure to the output of a diode-pumped, Ti: sapphire laser tuned to 730 nm. Results: Local uncaging of caged Ca ~ (2+) was able to trigger Ca ~ (2+) release events in both single cells and tissuestrips from mouse bladder. The Ca ~ (2+) release events could not be blocked byryanodine alone, but the property of the Ca ~ (2+) release wa s markedly altered. Surfactant, in the presence of ryanodine, Xestospongin C completely inhibited the Ca ~ (2+) release events both in single cell and tissue experiments. Conlusion: (1) Two photon flash photolysis (TPFP) triggers Ca ~ ) induced Ca ~ (2+) release. This process involves release of type 2 ryanodine receptor channels; (2) TPFPresults in the release of Ca ~ (2+) through inositol 1,4,5-trisphosphate receptors in the presence of phospholipase C activation .