Vestibular effects of antibiotics introduced in the inner ear. Behavioral and electrophysiological studies in the...

The aim of this study was to find a rapid and suitable method for testing the toxicity of drugs upon the vestibular end organs. The experiments were performed in the frog and the action of two antibiotics, streptomycin sulphate and penicillin G, was studied by carefully observing the equilibrium behaviour of the animals and recording the spontaneous activity of the nerve of the horizontal semicircular canal. The results obtained show that: 1) injection of streptomycin sulphate (20 microgram) directly into the labyrinthic cavity elicited disorders of the equilibrium and reduced the spontaneous activity of the horizontal canal nerve; 2) these disorders were reversible or not depending on the animal; 3) there is a good correlation between behavioral observations and electrophysiological data (i.e. the activity of the ampullary nerve was low in frogs whose behaviour was impaired at the time of sacrifice; the activity did not differ from controls when the normal behaviour was completely restored); 4) injection of penicillin G or 0.7% NaCl into the labyrinthic cavity had no effect on the equilibrium of the frogs or on the activity of the ampullary nerve; 5) intramuscular or intralymphatic injections of streptomycin sulphate produced a neuromuscular block but did not alter the activity of the ampullary nerve. In conclusion, the question of ototoxicity is discussed.