Quantitative autoradiography of 5-[H-3]6-cyano-7-nitro-quinoxaline-2,3-dione and (+)-3-[H-3]dizocilpine maleate binding in rat vestibular nuclear complex after unilateral deafferentation, with comparison to cochlear nucleus

The distributions of non-N-methyl-D-aspartate and N-methyl-D-aspartate receptors in the rat vestibular nuclear complex were estimated by quantitative autoradiography of 5-[H-3]6-cyano-7-nitro-quinoxaline-2,3-dione and (+)-3-[H-3]dizocilpine maleate binding, respectively. The binding of 5-[H-3]6-cyano-7-nitro-quinoxaline-2,3-dione in the vestibular nuclear complex was also compared with that in the cerebellar cortex and cochlear nucleus. Measurements were made in control rats and in rats with unilateral destruction of the inner ear and removal of the vestibular ganglion. Compared to the unlesioned side, 5-[H-3]6-cyano-7-nitro-quinoxaline-2,3-dione binding in the lesioned-side vestibular nuclear complex was decreased significantly in all regions at two to four postoperative days. However, the bilateral asymmetry disappeared in most regions by 30 days. 5-[H-3]6-Cyano-7-nitro-quinoxaline-2,3-dione binding increased in the molecular layer of the cerebellar cortex at 30 days after lesion, although there were no clear chances at two to seven days. 5-[H-3]6-Cyano-7-nitro-quinoxaline-2,3-dione binding in the cochlear nucleus decreased on the lesioned side, compared to the unlesioned side, in regions receiving significant auditory nerve innervation, but increased in the molecular layer of the dorsal cochlear nucleus. (+)-3-[H-3]Dizocilpine maleate binding in regions of the vestibular nuclear complex was reduced on the lesioned side, compared to the unlesioned side, after deafferentation, with the largest reductions usually al 30 postoperative days. It is suggested that: (i) non N-methyl-D-aspartate receptors are involved in synaptic transmission for both vestibular and auditory nerve fibers, while the involvement of N-methyl-D-aspartate receptors is less certain; (ii) unilateral deafferentation of the vestibular nuclear complex can result in bilateral asymmetries for non-N-methyl-D-aspartate and N-methyl-D-aspartate receptors, which are most prominent at earlier and later survival times, respectively; and (iii) vestibular compensation may involve regulation of both non-N-methyl-D-aspartate and N-methyl-D-aspartate receptors in the vestibular nuclear complex and activation of non-N-methyl-D-aspartate receptor-related processes in cerebellar cortex. (C) 1997 IBRO.