Biophysical Properties of ERG Channels in Octopus Neurons of Ventral Cochlear Nucleus

Objective: 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 (Kv 11.3). 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 octopus neurons of the ventral cochlear nucleus (VCN). Methods: 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. Results: In current clamp, application of ERG channel blockers, terfenadine (10 μM) and E-4031 (10 μM), significantly increased input resistance in all the cells (p<0.05). Also, in octopus cells, it was found that terfenadine (10 μM) and E-4031 (10 μM) significantly reduced threshold for induction of action potentials (AP) 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). Steady state activation curve for ERG tail current was determined with a half-activation voltage in Octopus cell V0.5 -50.72±0.32 with a slope factor of 6.04±0.23 mV (n=3). The quasy steady-state inactivation curve for chord conductances gave for Octopus cell V0.5 value of -74.34±0.46 and the slope of 7.89±0.32 (n=3). Conclusion: In conclusion, the findings obtained in the present study suggest that Octopus neurons express ERG channels and appear to threshold for AP induction and, possibly, resting membrane potentials in this cells.