Chloride current in urine-induced responses in isolated mouse VSNs. (A) Urine-induced inward currents decreased in the presence 300 µM of extracellular DIDS. The response recovered after DIDS was washed off. The cell was held at −80 mV and recorded with perforated patch clamp. The interval between urine applications was 2–3 min. (B) 300 µM niflumic acid, another chloride channel blocker, had a similar effect on urine-induced currents as DIDS. The response only partially recovered after niflumic acid was washed off. (C and D) In all the cells tested, DIDS and niflumic acid significantly inhibited the urine-induced inward current, suggesting the involvement of a chloride current in the response. The open circle is the value of the urine response normalized to the initial urine response in Ringer's (control) for each cell. The filled circles and error bars are the mean and SEM for the cells tested in the same conditions. The number of cells is listed on the top of each graph. **, P < 0.01, determined with repeated measures one-way ANOVA with Bonferroni test (C) and Friedman with Dunn test (D). DU, 1:500 dilute urine.