並列摘要
Amino acid L-glutamate was first proposed as a neuroexcitatory agent some thirty years ago, and appears to be one of the major excitatory neurotransmitters in the central nervous system. Besides its neuroexcitatory action, L-glutamate was also found to be neurotoxic. Excessive exposure to L-glutamate may kill the neuron. This phenomenon is called “excitotoxic-ity”, since the neurons are literally “excited to death”. Excitotoxicity has been consid-ered to be associated with various pathol-ogy in the central nervous system such as ischemia, epilepsy and some neurodegenera-tive diseases. In the cochlea, L-glutamate is also the best candidate as neuro-transmitters between inner hair cells and the primary afferent neurons. The presnta-tion of excitotoxicity in the inner ear includes swelling of the afferent nerve terminals and death of the spiral ganglion cells. These toxicity is probably mediated by both NMDA and non-NMDA receptors. Clinically, noise trauma, cochlear anoxia and neural type presbycusis may have close relationship with excitotoxicity.