ATP-induced current in isolated outer hair cells of guinea pig cochlea.
1. Electrical and pharmacologic properties of ATP-induced current in outer hair cells isolated from guinea pig cochlea were investigated in the whole-cell recording mode by the use of a conventional patch-clamp technique. 2. Under current-clamp conditions, rapid application of ATP depolarized the outer hair cells resulting in an increase in conductance. The ATP-induced response did not show any desensitization during a continuous application. 3. At a holding potential of -70 mV, the ATP-induced inward current increased in a sigmoidal fashion over the concentration range between 3 microM and 1 mM. The half-maximum concentration (EC50) was 12 microM and the Hill coefficient was 0.93. 4. The ATP-induced current had a reversal potential near 6 mV, which was close to the theoretical value (1 mV) calculated from the Goldman-Hodgkin-Katz equation for permeable intra- and extracellular cations. 5. In the current-voltage (I-V) relationship for the ATP response, a slight inward-going rectification was observed at more positive potentials than the reversal potential. 6. The substitution of extracellular Na+ by equimolar choline+ shifted the reversal potential of the ATP-induced current to more negative values. The substitution of Cs+ in the internal solution by N-methyl-D-glucamine+ (NMG+) shifted it in the positive direction. The reversal potential of ATP-induced current was also shifted to positive values with increasing extracellular Ca2+ concentration. A decrease of intracellular Cl- by gluconate- did not affect the reversal potential, thereby indicating that the ATP-induced current is carried through a large cation channel.(ABSTRACT TRUNCATED AT 250 WORDS)
Nakagawa
T
T
Department of Neurophysiology, Tohoku University, School of Medicine, Sendai, Japan.
Akaike
N
N
Kimitsuki
T
T
Komune
S
S
Arima
T
T
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D005260:Female; D006168:Guinea Pigs; D006198:Hair Cells, Auditory / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D010646:Phentolamine / Q000494:pharmacology; D011802:Quinidine / Q000494:pharmacology
D000255:Adenosine Triphosphate; D011802:Quinidine; D010646:Phentolamine