Quantitative immunogold cytochemistry reveals sources of glutamate releasein inner ear ischemia

Glutamate is thought to be a major neurotransmitter between hair cells and afferent dendrites in the inner ear. However, excessive glutamate is known to be excitotoxic, and may be involved in ischemic neuronal damage in the c entral nervous system. The glutamate concentration in the perilymph has bee n reported to increase during ischemia,but the source of glutamate is still nuclear. In the present study, ne have used post-embedding immunogold cyto chemistry to analyse changes in the cellular distribution of glutamate in t he guinea pig organ of Corti during ischemia. The areal gold particle densi ties in the inner hair cells of the ischemic side were fewer than those of the control side, indicating that glutamate may be released from the hair c ells during ischemia. Adjacent supporting cells (border cells) also showed a decrease in particle density, suggesting that they constitute an addition al source of glutamate.