Immunohistochemical Localization of NMDA Receptor in the Auditory Brain Stem of Postnatal 7, 16 Circling Mouse

Glutamate receptors may play a critical role in the refinement of developing synapses. The lateral superior olivary nucleus (LSO)-medial nucleus of trapezoid body (MNTB) synaptic transmission in the mammalian auditory brain stem mediate many excitatory transmitters such as glutamate, which is a useful model to study excitatory synaptic development. Hearing deficits are often accompanied by changes in the synaptic organization such as excitatory or inhibitory circuits as well as anatomical changes. Owing to this, circling mouse whose cochlea degenerates spontaneously after birth, is an excellent animal model to study deafness pathophysiology. However, little is known about the development regulation of the subunits composing these receptors in circling mouse. Thus, we used immunohistochemical method to compare the N-Methyl-D-aspartate receptor (NMDA receptor) NR1, NR2A, NR2B distribution in the LSO which project glutamergic excitatory input into the auditory brainstem, in circling mouse of postnatal (p) 7 and 16, which have spontaneous mutation in the inner ear, with wild-type mouse. The relative NMDAR1 immunoreactive density of the LSO in circling mouse p7 was 128.67±8.87 in wild-type, 111.06±8.04 in heterozygote, and 108.09±5.94 in homozygote. The density of p16 circling mouse was 43.83±10.49 in wild-type, 40±13.88 in heterozygote, and 55.96±17.35 in homozygote. The relative NMDAR2A immunoreactive density of LSO in circling mouse p7 was 97.97±9.71 in wild-type, 102.87±9.30 in heterozygote, and 106.85±5.79 in homozygote. The density of LSO in p16 circling was 47.4±20.6 in wild-type, 43.9±17.5 in heterozygote, and 49.2± 20.1 in homozygote. The relative NMDAR2B immunoreactive density of LSO in circling mouse p7 was 109.04±6.77 in wild-type, 106.43±10.24 in heterozygote, and 105.98±4.10 in homozygote. the density of LSO in p16 circling mouse was 101.47±11.5 in wild-type, 91.47±14.81 in heterozygote, and 93.93±15.71 in homozygote. 이 연구는 2008년도 단국대학교 대학연구비의 지원으로 연구되었음. * Correspondence should be addressed to Myeung Ju Kim, Department of Anatomy, College of Medicine, Dankook University, San # 29, Anseo-dong, Cheonan-si, Chungnam 330-714, Korea. Ph.: (041) 550-3856, Fax: (041) 556-6461, E-mail: [email protected]