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.


CONCLUSIONS
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.
Kimitsuki
Takashi
T
Department of Otorhinolaryngology, Miyazaki Medical College, 5200 Kihara, Kiyotake-cho, Japan. kimituki@fc.miyazaki-med.ac.jp
Nakashima
Takahiro
T
Kawano
Hirokazu
H
Komune
Shizuo
S
D000818:Animals; D006168:Guinea Pigs; D006199:Hair Cells, Auditory, Inner / Q000502:physiology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000502:physiology; D020933:Neurotrophin 3 / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology*
D020933:Neurotrophin 3; D015221:Potassium Channels