Electrical activity of isolated semicircular canal in the frog. Action of streptomycin.

1. An isolated frog semicircular canal was placed in a two-compartment perspex chamber which allowed the fluids bathing the inside (endolymph) and the outside (perilymph) of the canal to be replaced separately. Mechanical stimulation (MS) of the ampullar receptors was performed by sinusoidal cupular movement. 2. Streptomycin sulfate in the perilymph reduced promptly, strongly and reversibly nerve spontaneous activity (SA) recorded on the ampullar nerve. Streptomycin sulfate also reduced reversible and weakly the slow potentials recorded either near the crista ampullaris (Adc) or on the ampullar nerve (Ndc) and the modulation of firing rate (delta Fms) all these activities being evoked by a mechanical stimulation. 3. Streptomycin sulfate injected into ampullar endolymph reduced promptly and strongly the Adc, Ndc, and delta Fms. When its concentration was higher 0.2 mg/ml, the SA was also reduced about 40 min later. 4. It is concluded that streptomycin sulfate alters weakly and reversibly spike generation process and synaptic transmission; it inhibits strongly and reversibly the resting discharge and it inhibits strongly and may be partly reversibly the transduction mechanisms.