| Glutamate is the main neurotransmitter of excitatory synaptic transmission in afferent nerve system of cochlear. Meanwhile,many researches have indicated that ischemia,oxygen deficiengcy and excessive sound stimulus all induce inner hair cell and supporting cell to release excess glutamate which poison the hair cell, afferent neurofibers,ganglion spirale.The study of central nervous system showed that glutamate transporter performed the important effect in reuptake of glutamate from synaptic cleft.Aim The purpose of this study is to investigate the distribution and functions of glutamate-aspartate transporter in the cochlea of guinea pig. Immunohistochemistry was used to investigate the expression of GLAST in the cochlea of the guinea pig. By perfusing the antibody to GLAST to the cochlea that raised against the GLAST, the auditory brainstem response and the pathologic morphour were observed.Methods Immunohistochemistry and image analysis were used to investigate the expression of GLAST in the cochlea of the guinea pig. The antibody to GLAST was taken the place of PBS in Control group.Byperfusing the antibody to GLAST to the cochlea that raised against the GLAST, the auditory brainstem response and the pathologic morphour were observed. The antibody to GLAST was taken the place of artificial perilympha in Control group. Results1. The staining for GLAST in inner ear of the guinea pig showed a strong reactivity in the inner and outer hair cells,inner and outer pollar cells,supporting cells, marginal cells of stria vascularis,spiral limbus epithelium, spiral ganglion cells.Specially,the GLAST-IR was stronger in inner and outer hair cells,inner and outer pollar cells, spiral ganglion cells and the Deiters'cell than in Hensen cell, Claudius cell, marginal cells of stria vascularis and spiral limbus epithelium.The GLAST-IR positive products could not be observed in the dendrons and axons of spiral ganglion cells.2. By the image analysis to GLAST-IR positive products in cochlea,the GLAST-IR was stronger in the second turn of inner hair cell of the normal guinea pigs than others turns of inner hair cell (P<0.05). The variability of density of GLAST-IR positive products in others turns was not significant (P>0.05). The variability of density of GLAST-IR positive products in four turns of outer hair cell was significant and from the first turn to the fourth turn(.P<0.05),the density of GLAST-IR positive products decreased progressively.3. Surveying the ABR thresholds:The variability of the ABR thresholds between Experimental group and Control group was not significant before the operations.The ABR was always not educed in the Experimental group after operations. At third day after operation,the ABR could be educed in only two guinea pigs in Control group and the thresholds had developed up to 70—80dB SPL.At sixth day after operation,the ABR could be educed in all guinea pigs in Control group and the threshold was 62.5 ± 5.25 dB SPL. At ninth day after operation,the ABR could be educed in all guinea pigs in Control group and the threshold was 47.5±6.18dB SPL.By statistical analysis,the thresholds at the different experimental time points had statistical difference in Control group(P<0.05).4. Morphological results:Basilar membrane strethched preparation showed that morphous of hair cell was normal on the whole in cochlea of Control group, but,lighter damages in outer hair cell occurred at the first turns.In Experimental group,the worst serious damages of cochlear hair cells were showed in the first turns of basilar menbrane,and damages in the lower turns were lighter.And damages of outer hair cells were getting heavier from 3rd row to 1st row. Transmission electron microscope showed that edema of hair cells,swelling of mitochondria,and injury of nerve fibers in the Experimental group. Morphological changes also occurred in Control group,but were lighter than those of Experimental group.Conclusions1. The GLAST extensively distribute in the inner and outer hair cells,inner and outer pollar cells,supporting cells, marginal cell of stria vascularis,spiral limbus epithelium and spiral ganglion cells of cochlea of guinea pigs . GLAST-IR was stronger in inner and outer hair cells,inner and outer pollar cells, spiral ganglion cells and the Deiters'cell than in Hensen cell, Claudius cell, marginal cells of stria vascularis and spiral limbus epithelium.2. By the image analysis to GLAST-IR positive products in cochlea,the GLAST-IR was stronger in the second turn of inner hair cell of the normal guinea pigs than others turns of inner hair cell (P<0.05). The variability of...
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