Electrophysiological investigation of ERG channels in the cochlear nucleus neurons

ERG (Ether a go go related gene) channels (Kv 11) are the members of the voltage-dependent potassium channel family, which have three subtypes as ERG1 (Kv 11.1), ERG2 (Kv 11.2), ERG3 (Kv11.3). Electrophysiological, biophysical properties of ERG channels and their functions are not known in the cochlear nucleus (CN) neurons, which is the first relay station of auditory pathway. For that reason, we aimed to study pharmacological and biophysical properties and their functions in the stellate, bushy and octopus neurons of the ventral cochlear nucleus (VCN). A total of 70 mice at 14-17 day-old were used for this study. Electrophysiological characterization of ERG channels was performed using patch clamp technique in CN slices. In current clamp, application of ERG channel blockers, terfenadine (10 µM) and E-4031 (10 µM), significantly increased input resistance in all the three cell types (p<0,05. In stellate cell, they also increased a spontaneous activity and frequency of action potential (AP) induced by square current pulse (p<0,05). In all the cell types, it was found that terfenadine (10 µM) and E-4031 (10 µM) significantly reduced threshold for induction of APs with square current pulses (p<0,05). Tail ERG currents were measured under voltage-clamp. Steady state activation curve for ERG tail current was determined, yielding a half-activation voltage (V0,5) and slope factor (k factor) of approximately -50 mV and 7 mV respectively for all the three cell types. Steady-state inactivation curve had half-inactivation voltages (V0,5) and k factors between -70, -78 mV and 7-10 mV respectively. In conclusion, the findings obtained in the present study suggest that ERG channels appear to contribute AP frequency in stellate cells, threshold for AP induction by current injection and resting membrane potentials in all the three cell types.