INFLUENCE OF OTOTOXIC PHARMACEUTICALS ON BIOELECTRIC RESPONSES IN CEREBRAL CORTEX AND COCHLEA

Abstract

The article describes the results of the experiment aimed to find out the nature of changes in the excitability of the auditory cortex during prolonged taking of antibiotics, aminoglycosides, diuretics and salicylates. Methodology. The series of experiments was carried out on cats of both sexes weighing 3-3.5 kg, in natural behaviour. Rectangular threshold (1.5-3 V) and supra-threshold (5-7 V) electrical impulses lasting 0.1 ms were applied to the TCR fibres, using single and paired (interstimular intervals of 20-500ms) stimulation of the TCR fibres. As a source of irritating impulses, a multi-channel stimulator "SEN-3201" of the company "Nikon-Kohden" (Japan) was used. For each skeletal interval was carried out on 10 repetitions. The SOFTWARE was registered using the average Det-1100 average from Nikon-Kohden (Japan). The resulting visual control was performed from the screen of the "Disa-Indicator" oscilloscope (Denmark). The maximum level of the intensity value reached 110 dB. Sound signals were transmitted through special high-frequency phones (or speakers) of the GD-4 type, which were in a free state, at a distance of 10 cm from the ear of the test ear. All the studied pharmaceuticals (furosemide, streptomycin, gentamicin, kanamycin, monomycin, tobramycin and amikacin) except acetylsalicylic acid, which was injected intraperitoneally, were administered to cats intramuscularly 2 times a day at intervals of 10-12 hours. Bioelectric reactions of the cortex and cochlea were recorded daily 2-3 hours after the next administration of drugs. Streptomycin, kanamycin and monomycin were used at a dose of 40 mg / kg, which causes inhibition of the cochlea's MIC response (MOI) and auditory nerve PD only with long-term use. Gentamicin, tobramycin and amikacin were administered in a lower (15 mg/kg) dose. Results. Furosemide reduced by 50% the value of the microphone potential recorded during sound stimulation with a frequency of 10 kHz after 4 days, with a frequency of 1 kHz-5 days, with a frequency of 0.5 kHz-6 days from the beginning of use. The most sensitive to furosemide were auditory nerve PD, which occurred during sound stimulation at a frequency of 10 kHz (T50 – 5 days), and less – at a frequency of 0.5 kHz (T50 – 7 days). The cancellation of furosemide was accompanied by the restoration of the value of these bioelectric reactions to the initial level in 5 days. Thus, the data obtained indicate the possibility of a reversible depressing effect of furosemide on the responses of the CGM and the cochlea that occur on sound stimulation. All the studied antibiotics-aminoglycosides had the ability to reduce the value of the testing primary response when paired electrical stimulation of TCR fibres. These changes were observed 2-3 days after the start of the use of antibiotics. Initial changes in the value of MP and PD of the auditory nerve occurred after 12-24 times of drug administration. In this case, a decrease in these potentials by 20-25% was noted. Further use of antibiotics led to an increase in changes in responses registered in the cochlea, with the greatest sensitivity to the effects of drugs were reactions to high-frequency sound stimuli. When analyzing the ability of the studied tools to disrupt the activity of the peripheral fragment of the auditory analyzer, a pattern similar to that for the cerebral cortex was found. Withdrawal of drugs at the stage of initial changes in potentials registered in the cochlea is not accompanied by their recovery for a long (6 weeks) period after stopping the administration of antibiotics. Conclusions. Different rates of formation of damage to interneuronal transmissions were found during long-term use of different antibiotics.