Neurotrophin-3 modifies potassium currents in isolated inner hair cells from guinea-pig cochlea

Objective: Neurotrophins elicited short-term glutamate release from the presynaptic locus. The aim of this study was to investigate short-term effects of neurotrophin-3 (NT-3) on the membrane current of inner hair cells (IHCs). Methods: IHCs were isolated from the guinea-pig cochlea. Membrane currents were measured by conventional whole-cell voltage-clamp recordings. NT-3 was dissolved in a standard external solution and applied to the IHCs under pressure using pipettes. Results: Six out of eight IHCs demonstrated a suppression of K currents by extracellular application of NT-3. At +60 mV, the amplitudes of the outward current in the control and NT-3 solutions were 5.6±1.3 and 4.2±1.0 nA, respectively. NT-3 suppression was voltage-independent. One cell showed an immediate suppression with NT-3 and the following potentiation during washing with standard saline. Conclusion: NT-3 suppressed the amplitude of K current on IHCs, suggesting that neurotrophins are capable of potentiating the hair cells’ excitability. Neurotrophins may have a therapeutic value in the prevention and treatment of hearing impairment caused by inner ear damage.