Heterogeneous voltage-dependence of inward rectifier currents in spiral ganglion neurons. Zun-Li Mo and Robin L. Davis. Department Biological Sciences, Rutgers University, Piscataway, New Jersey, 08855-1059, U.S.A.
APStracts 4:134N, 1997.
ABSTRACT
Inward rectification was characterized in neonatal spiral ganglion neurons maintained in tissue culture. Whole-cell current and voltage clamp techniques were used to show that the hyperpolarization-activated cationic (Ih) current underlies most or all of the inward rectification demonstrated in these neurons. The average reversal potential (-41.3 mV) and cesium-sensitivity were typical of that found in other neurons and cell types. What was unique about the hyperpolarization activated currents, however, was that the half maximal voltages (V1/2) and slope factors (k) that characterized Ih current activation were graded from neuron to neuron. Voltage clamp recordings made with standard bath and pipette solutions revealed V1/2 values that ranged from -78.1 to - 122.1 mV, with slope factors from 7.6 to 13.1. These gradations in the voltage dependent features of the Ih current did not result from variability in the recording conditions because independently measured Na+ current-to-voltage relationships were found to be uniform (peak current at -20 mV). Moreover, the range and average V1/2 and slope values could be altered with activators (8- CPT-cAMP in combination with OA) or inhibitors (H-89) of PKA indicating that Ih current heterogeneity most likely resulted from differential phosphorylation. 

Received 8 May 1997; accepted in final form 16 July 1997.
APS Manuscript Number J378-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 27 August 1997