Objective     To explore the role of adenosine triphosphate (ATP) in the detrusor muscle from unstable bladders of rats.      Methods     There were 30 female Sprague-Dawleys (SD) rats in bladder outlet obstruction (BOO) group and 15 female SD rats in control group. The bladders from 10 rats from each group were incubated in 37 ℃ Kreb solution. After a bolus infusion of sodium chloride

ATP and  pyridoxalphosphate-6-azophenyl-2’4’-disulfonic (PPADS) were infused into the in vitro bladder respectively

and then the bladders were pumped with sodium chloride at 0.1 ml/min for 4 min. A cystometry was performed at the same time for 8 min. Later

ATP was added into the incubation solution with or without incubation of PPADS previously and cystometry was recorded simultaneously. The bladder pressure curves were recorded and the pressure of in vitro bladders at the time points of 20 s

50 s

4 min

8 min were measured.      Results     For the bladder pressure curve and bladder pressure at different time points

there was no significant difference in each group and between the two groups when the drugs were given into bladders. There was a distinctive bladder contraction when ATP was added into the incubation solutions .The bladder pressure of control group was higher than that of BOO group at 50 s (P0.01). However

the amplitude of bladder contraction was decreased dramatically when the bladder was incubated previously with PPADS. There was no dramatical difference in the bladder pressure between the two groups.      Conclusion     ATP given intravesically or released by the urothelium cells plays a role in the urinary frequency and detrusor instable contraction through nervous reflex. The ATP released by the bladder purinergic nerves can induce detrusor contraction directly.