Changes in Ih properties in bladder ICC-LCs. (a) Characteristic traces of Ih currents in the bladder ICC-LCs of naive or CYP-treated WT and HCN1−/− mice evoked by a voltage-clamp protocol with a holding potential of −60 mV and a step potential ranging from −60 to −120 mV in decrements of 10 mV. Application of ZD7288 (50 μM) reduced Ih amplitudes in all four groups. (b) RT-PCR showed that only c-kit and GAPDH expression was visualized in the lanes, confirming the reliability of the isolated bladder ICC-LCs. (c) Fully activated current traces of Ih evoked at −120 mV, showing that CYP treatment significantly elevated Ih current amplitudes and HCN channel gating rates in WT and HCN1−/− mice, while HCN1 channel deletion significantly decreased Ih current amplitudes and HCN channel gating rates in CYP-treated and naive mice. Over a voltage range of −60 to −120 mV, (d, e) CYP-treatment significantly increased Ih current density in WT and HCN1−/− mice (data represent the mean±s.d., N=10, *P<0.05, **P<0.01 and ***P<0.001, versus naive mice), (f, g) while HCN1 channel knockout significantly decreased Ih density in CYP-treated and naive mice (data represent the mean±s.d., N=10, *P<0.05, **P<0.01 and ***P<0.001, versus WT mice).