To investigates the effects of water avoidance stress on voiding behaviour and functional bladder responses in mice.

Mice in the Stress group were exposed to water avoidance stress (WAS) for 1 h/day for 10 days, Controls were age-matched and housed normally. Voiding behaviour was measured periodically throughout the stress protocol and bladders were isolated 24-h after final stress exposure to measure bladder compliance, spontaneous phasic activity, contractile responses, and release of urothelial mediators.

Repeated stress exposure induced a significant increase in plasma corticosterone levels in the WAS group compared to control. An overactive bladder phenotype was observed in WAS mice, causing a significant increase in the number of voiding events observed from as early as day-3, and a 7-fold increase following 10-days' stress. This increase in voiding frequency was associated with a significant decrease in void size, an increase in the number of small voids, but no change in total voided volume. Bladders from stressed mice showed a significant increase in the maximum responses to the muscarinic agonist carbachol (p < 0.01), in addition to enhanced pressure responses to the purinergic agonists ATP (p < 0.05) and αβ-mATP (p < 0.05), and non-receptor mediated contractions to KCl (p < 0.05) compared to controls. Nerve-mediated bladder contractions to electric field stimulation were not significantly affected by stress, nor were spontaneous phasic contractions or release of urothelial ATP and acetylcholine.

Repeated exposure to water avoidance stress produced an overactive bladder phenotype, confirmed by increased voiding frequency, and associated with enhanced bladder contractile responses.