Effect of Ethylalcohol and Pentobarbital Sodium on the Acoustic Middle Ear Reflex in Man

Abstract

The effect of ethylalcohol and pentobarbital sodium on the acoustic middle ear reflex in man was studied by recording the change in the ears' acoustic impedance before and after oral administration of ethyl-alcohol, giving blood alcohol concentrations from 0.02 to 0.15%, and pentobarbital in doses from 1.5 to 4.3 mg/kg. The reflex was elicited by bursts of pure tones (500 and 1450 cps) and the response was recorded in both ears simultaneously when either the right or the left ear was stimulated. Thus, the effect on the crossed and the uncrossed reflexes was studied.

It was found that both ethanol and pentobarbital have a depressive effect on the reflexes. The crossed and the uncrossed reflexes were equally sensitive to ethanol while the crossed reflex was more sensitive to pentobarbital than the uncrossed. In addition, the slope of the stimulus-response curve of the crossed reflex was diminished by pentobarbital, while ethanol did not change the slope of the crossed and uncrossed reflexes. The results are discussed in relation to studies on the sensitivity of spinal reflexes to ethanol and barbiturate. The consequences of diminished middle ear muscle activity caused by the drugs for sound-induced damages on the inner ear are emphasized.