Comparative study of the influence of aminoglycoside antibiotics on the activity of the horizontal semicircular canal in the frog.

This work is an electrophysiological study made in the frog. The technique allows one to test and to compare the actions of a number of aminoglycoside antibiotics, directly introduced into the labyrinthic cavity, on the spontaneous activity of a vestibular receptor--the horizontal semicircular canal. The effects of aminoglycoside solutions have been compared with those of physiological solutions (NaCl 7 g/l, Ringer) and of penicillin (not ototoxic). The results obtained show: (1) After the introduction of a physiological solution the activity disappears only very briefly (electrical artefact, probably); after a few minutes the activity returns to its initial value. A similar phenomenon is obtained with penicillin. (2) When used at a dose of 10 microgram, all the aminoglycosides studied generally induced an important and lasting decrease in semicircular canal activity. (3) These aminoglycosides have been classified according to their vestibular local toxicity. Their descending order of influence is as follows: streptomycin, dihydrostreptomycin, amikacin (BBK 8), neomycin, sisomycin, gentamicin and lividomycin, tobramycin, kanendomycin. (4) A parallel can be drawn between local vestibular toxicity and clinical ototoxicity. The role and importance of the hemolabyrinthic barrier are noted and the notion of ototoxicity is discussed.