Urge incontinence and bladder dysfunctions are highly prevalent in the aging population with a huge financial cost(1). However, the underlying mechanisms are poorly understood. Recent evidence suggests that transient receptor potential vallinoid 4 (TRPV4) channels present in the urothelium, which facilitate Ca2+ influx, may serve as key sensory molecules in response to noxious stimuli and bladder stretch. We previously demonstrated that this receptor is functional in native bladder tissue, triggering release of ATP from the urothelium. This study tested the hypothesis that the expression of TRPV4 receptors was altered in aging bladders. Bladder tissues were obtained from young (2-5 months) and aging (24-36 months) guinea-pigs (GP) (male Dunkin-Hartley, schedule-1 procedure) in compliance with UK and EU regulations. Immunohistochemistry and Western blotting were employed to detect TRPV4 expression. Fixed full-bladder wall slices (14 microns) were probed for TRPV4 and examined by confocal microscopy. The presence of TRPV4 in mucosal and denuded smooth muscle lysates was evaluated using a standard Western blotting protocol and the relative expression analysed. Mucosal and intact smooth muscle strips were isolated from GP bladders and superfused with a Tyrode’s solution. The superfusate adjacent to the tissue was sampled and measured for ATP release using luciferin-luciferase assay(2). Positive staining for TRPV4 was observed in both young and aging GP bladders. Quantification of relative band intensity from Western blots by densitometry revealed a significantly greater mean TRPV4 expression (7 fold) in aging mucosa than young (arbitrary units normalised to loading control – aging: 65.0±11.6, young: 9.2±1.2; mean ± SEM, n=5, p<0.05, Mann-Whitney) and (6 fold) in smooth muscle (aging: 23.5±1.9, young: 3.8±2.7; n=5, p<0.05). Additionally, TRPV4 expression in the aging mucosa was significantly greater compared to smooth muscle (Mann-Whitey, n=5, P<0.05), which was not seen in young tissue. TRPV4 activator GSK1016790A (GSK, 1μM) triggered significant increase in ATP release in tissue preparations from both GP groups (young GP – mucosa: 281±60% of control; full thick strip: 346±40% of control; aging GP – mucosa: 232±47% of control; full thick strip: 269±40% of control; mean ± SEM, n=9, p<0.05, Wilcoxon’s). No significant difference in receptor-activated ATP release was observed between GP age-groups. These results provide the first evidence that TRPV4 expression is altered in bladders with increasing age. The up-regulated expression of TRPV4 receptors and their abundance in the urothelium indicate that these receptors may contribute to the urothelium-mediated sensory dysfunction during aging. This highly increased TRPV4 expression may influence bladder function through altered Ca2+ entry or other signalling pathways independent from ATP release.