Low Doses of Aminoglycosides Alter the Action Potential Tuning Curve Without Change in Threshold Sensitivity

Abstract

Compound auditory nerve action potentials (CAP) have been extensively used in the evaluation of drug ototoxicity. Electrophysiological changes observed after aminoglycoside treatment consist of a threshold elevation, an increase in CAP latency near threshold, and a modification of the amplitude of the CAP response as a function of the stimulus intensity (amplitude-intensity function) (see Aran, 1981). The action potential timing curves (APTC) measured with either a forward or a simultaneous masking paradigm also reveal a deterioration in cochlear frequency selectivity in aminoglycoside-treated animals (Harrison and Aran, 1981). However, these alterations have only been observed with high doses of antibiotics and very few reports have been concerned with the early detection of CAP changes following low-dose aminoglycoside treatment. The purpose of the present paper was to investigate in the rat the dose-dependent changes following administration of a range of amikacin doses, with emphasis on the effects of a weak intoxication.