Action of streptomycin and calcium on the apical membrane of hair cells of the frog isolated semicircular canal.

Abstract

An isolated frog posterior semicircular canal was placed in a two-compartment perspex chamber allowing separate perfusions of the peri- and endolymphatic space with adequate saline solutions. The ampullar receptors were mechanically stimulated with a hydraulic device which imposed sinusoidal movements to the cupulo-endolymphatic system at low frequency (0.10 Hz). Slow potentials recorded with non-polarizable Ag/AgCl electrodes near the crista ampullaris (Adc) and on the ampullar nerve (Ndc) were displayed together with an analog signal of the mechanical stimulation and with the nerve spike frequency, on a strip chart. The streptomycin action or the high calcium concentration action (these two substances being administered together or separately into the ampullar space) indicated that the streptomycin seemed to block mechano-dependent channels (non-specific) assumed to be included into the hair cell apical membrane. The synaptic transmission process was altered by streptomycin but was improved by the high calcium concentration. Also, the mechanisms which would control the spontaneous release of a neurotransmitter, seemed, at least partly, different from those controlling the neurotransmitter release in response to a mechanical stimulation; these last ones were less sensitive to the calcium action.