Interstitial cells (ICs), analogous to the interstitial cells of Cajal in the gut, may generate phasic activity (PA) in smooth muscle tissues, including the bladder. An established marker of the ICs is c-kit [1]. However, recent studies have shown that Anoctamin-1 (Ano1, Tmem16a), a Ca2+ activated chloride channel (CaCC), influences generation of pacemaker activity in gut ICs and therefore can be used as a novel marker for these cells [2]. CaCC blocking drugs such as niflumic acid were able to alter the pacemaker activity of the ICs in the gut and thus may be important modulators of these cells in other tissues. Thus, the aim of this study was to investigate whether Ano1 is expressed in porcine bladder and to explore the role of niflumic acid in modulating the PA of bladder tissue. Methods: Female pig (~6months old) bladders were obtained from the local abattoir, hence ethical approval was unnecessary. PCR was carried out on the c-DNA synthesized from total RNA isolated from bladder mucosa (composed of the urothelium, lamina propria and muscularis mucosa) and denuded detrusor. Primers were designed for Sus scrofa Ano1 mRNA (XM_003122417.2). PCR products were separated by electrophoresis and sequenced. Longitudinal strips of denuded detrusor (n=7) or mucosa (n=47) were mounted in perspex microbaths and superfused with Krebs’ solution at 37°C. Isometric tension was measured via UF1 force transducers connected to a Powerlab system using the LabChart software. Denuded detrusor strips were superfused constantly with 0.1µM carbachol (CCh) solution to induce PA. The effect of increasing concentrations of niflumic acid (1-30µM added cumulatively, 10-min exposure for each concentration) or drug vehicle (DMSO) on spontaneous and CCh-stimulated PA was investigated by measuring the amplitude and frequency of PA. All data is expressed as mean±SEM. Statistical analysis was carried out by using repeated measure ANOVA followed by Dunett’s post hoc test. Results: Ano1 mRNA expression was found in both mucosal and detrusor layers of porcine bladder. Niflumic acid did not have a significant effect on the amplitude or the frequency of CCh-stimulated PA in the denuded detrusor strips at all concentrations. However, the amplitude of basal PA in mucosal strips was significantly reduced (p<0.001) with 10µM (22.3±4.6% inhibition) and 30µM (26.6±4.4% inhibition) niflumic acid. The frequency of basal mucosal contractions was reduced only at 30µM (25.0±7.7% inhibition) niflumic acid (p<0.001). Drug vehicle had no effect on PA. Discussion: Inhibition of mucosal PA but not cholinergic-induced detrusor PA by niflumic acid, may suggest a role of ANO1 channels in mediating the PA of ICs found in the suburothelial layer of mucosal strips, while not affecting direct muscle stimulation by CCh.