Hypothermia reduces glutamate efflux in perilymph following transient cochlear ischemia

The effect of hypothermia on ischemic injury of the cochlea in gerbils was studied with particular regard to glutamate efflux in the perilymph. Under normothermic conditions interruption of the blood supply to the cochlea for 15 min caused a remarkable elevation of the compound action potential (CAP) threshold, and an increase in perilymphatic glutamate. The CAP threshold recovered to some extent with reperfusion, but not to preischemic levels. CAP threshold, under hypothermic conditions and with reperfusion, recovered promptly to near preischemic levels, while glutamate concentration did not change. These results, together with electron microscopy studies, suggest that hypothermia prevents hearing loss primarily through reduction of glutamate efflux at the synopses between inner hair cells and primary afferent auditory neurons. NeuroReport 12: 1983-1987 (C) 2001 Lippincott Williams & Wilkins.