Putative amino acid neurotransmitters in cochlear (CN) and vestibular (VN) nuclei of guinea pig

Abstract

We reported that aspartate (asp) and glummate (glu) are significantly reduced in the ventral CN after surgical destruction of the organ of Corti, corresponding to the pattern of primary innervation [Thaimann et al., J. Acoust. Soc. Am. Suppl. 1 67, S77 (1980)]. More recently, we confirmed and extended Wenthold's finding [Brain Res. 143, 544 (1978)] that these substances decline similarly, although on a faster time scale, after VIIIth nerve section–no decline in molecular and fusiform layers of dorsal CN, but significant declines (p < 0.001) in deep dorsal CN (asp 29%, glu 24%) and in posteroventral CN (asp 48%, glu 45%). Analogous declines occurred in the phylogenetically older VN following VIIIth nerve section. In the heavily innervated central part of superior VN asp and glu decreased by 21% and 37%, respectively (p < 0.001), with no decline in the sparsely supplied peripheral part. In lateral VN, asp and glu declined significantly (35% and 21%, respectively) in the heavily innervated ventral portion, while in the sparsely innervated dorsal part, only asp declined (26%). The behavior of asp and glu after lesion (as well as their resting distribution) is consistent with the involvement of either or both in neurotransmission at the primary auditory and vestibular terminals. [Supported by NIH.]