The emergence of free radicals after acoustic trauma and strial blood flow.

The effect of acoustic trauma on cochlear strial circulation was investigated immunohistologically in the guinea pig. Kanamycin was used as a tracer of blood flow. Moreover, histochemical examinations were made to reveal the emergence of free radicals in the cochlea following acoustic trauma. At 5 min (5 min after intense sound exposure 120-125 dB SPL, 3 h) the blood flow in the stria vascularis was greatly diminished. At 2 h the strial blood flow started to recirculate and at 6 h it appeared to have returned to normal. Superoxide anion radicals (O2-) emerged along the luminal membrane of the marginal cells of the stria vascularis at 5 min. O2- disappeared at 30 min, but reappeared at 2 h. The cause of its emergence at 5 min was obscure. However, the strange phenomenon that O2- emerged again at 2 h seemed ascribable to the re-circulation of strial blood flow after sound exposure.