[The effects of Streptolysin-O and sodium hyaluronate on the permeability of the round window membrane in guinea pigs--an electrophysiologic study]

Abstract

Background: The round window membrane (RWM) acts like a barrier for topically applied substances into the middle ear preventing diffusion into the perilymphatic fluid compartment.

Material and method: In an animal model, modulation of the permeability of the RWM was attempted using Streptolysin-O (SLO) in various concentrations and sodium hyaluronate. Thereafter, the effect of intratympanically applied Lidocain 2 % on hearing threshold measured by auditory brainstem response was tested for Lidocain 2 % and Lidocain 2 % in combination with SLO or sodium hyaluronate.

Results: The results show that both, SLO and sodium hyaluronate, influence the effect of Lidocain 2 % on hearing thresholds as an indirect sign for changes of the permeability of the RWM. However SLO by itself in low concentrations decreased auditory thresholds in some animals while this was never observed with sodium hyaluronate.

Conclusions: Our findings preclude SLO and favor sodium hyaluronate as a modulator of RWM permeability in therapeutic trials.