Distribution of aspartate and glutamate in cochlear nucleus (CN) following destruction of organ of Corti (OC) Free

Webster and Webster [ORL 86, 342 (1978)] have shown that degenerative changes in the CN are maximal three weeks after surgical destruction of the OC in the guinea pig. A1 this time aspartate and glutamate are reduced by 28% (p < 0.05 or better) and 19% in the anteroventral CN, and 25% and 23% in the posteroventral CN, respectively, when compared to the opposite, nonoperated side. Both regions receive heavy primary innervation. Only minimal changes occur in the molecular and fusiform layers of the dorsal CN, regions receiving little primary innervation. In the deep dorsal CN, with moderate innervation, aspartate and glutamate are reduced by 13% and 10%, respectively. These results support the concept that these substances may be involved in primary afferent transmission in the CN. By comparison, aspartate and glutamate are only 17% and 11% lower in the whole CN of 90 day old Waltzing guinea pigs (a mutant in which the OC degenerates within several weeks after birth) than in controls [Wenthold and Gulley, Brain Res. 158, 295 (1978)]. Subdivision of the CN should show changes closer to those following surgical destraction of the OC. [Supported by NIH.]