Intact blood-perilymph barrier in the rat after impulse noise trauma

Conclusion. The permeability of the blood-labyrinth barrier for radioactive mannitol was unchanged after impulse noise trauma. The present findings are contradictory to the theory of an increased permeability in the blood-labyrinth barrier as a result of extensive noise exposure. Objective. Noise trauma is reported to cause multiple effects on the cochlea including mechanical and metabolic damage. The aim of the study was to observe the effects of impulse noise on cochlear homeostasis. Materials and methods. A well-established rat model was used for evaluation of the early effects of impulse noise trauma on the integrity of the blood-perilymph barrier. To evaluate whether a blood-perilymph barrier disruption contributes to cochlear injury after impulse noise, the paracellular transport of radioactive mannitol into scala vestibuli perilymph (PLV) and electrolyte concentration in perilymph were estimated. Thirteen animals exposed to synthesized impulses of 160 dB SPL peak value, at a rate of 100 pulses, were designed as the study group and 15 rats not exposed to noise were designed as the control group. After mannitol infusion each ear of the animal in the study group was separately exposed to impulse noise and PLV samples were taken during 2 h post-infusion. In the control group, corresponding PLV samples were taken after mannitol injection. Results. At 2 h after mannitol infusion there was no difference in PLV mannitol concentration in the study group and control group (21.5% +/- 2.2 and 20.5% +/- 2.1, respectively). Impulse noise had no effect on the electrochemical composition of PLV.