Age-related changes in the expression of NMDA, serotonin, and GAD in the central auditory system of the rat.

Hyun Joon Shim, Lae Hyung Lee, Youngbuhm Huh, So Yoon Lee, Seung Geun Yeo

Department of Otorhinolaryngology, Eulji Hospital, Eulji University School of Medicine, Seoul, Korea.

Acta oto-laryngologica 2012 Jan

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We suggest that age-induced changes of serotonin, N-methyl-d-aspartate receptor (NMDAR), and glutamate decarboxylase (GAD) expression in rats are dependent on the specific location in the central auditory system (CAS). Despite the importance of understanding changes in neurotransmitters during presbycusis, only a few studies have assessed age-associated changes in neurotransmitter at each level of the CAS. We therefore evaluated effects of aging on neurotransmission in the CAS of rats. The concentrations of serotonin, NMDAR, and GAD were assayed immunohistochemically in the cochlear nucleus (CN), superior olivary nucleus (SON), inferior colliculus (IC), medial geniculate body (MGB), and auditory cortex (AC) of Sprague-Dawley rats, aged 2 weeks (n = 20) or 24 months (n = 20). The total number of neuronal cell bodies of the CAS did not differ significantly at each level between young and aged rats (p > 0.05). Serotonin expression was increased with age in the IC and MGB, but decreased in the CN, SON, and AC (p < 0.05). NMDAR was significantly higher in the CN, MGB, and AC of aged compared with young rats, but was significantly decreased over time in the SOC and IC (p < 0.05). GAD67 was increased with age in the MGB and AC and decreased in the CN and SON (p < 0.05), but was not changed in the IC.

Citation

Hyun Joon Shim, Lae Hyung Lee, Youngbuhm Huh, So Yoon Lee, Seung Geun Yeo. Age-related changes in the expression of NMDA, serotonin, and GAD in the central auditory system of the rat. Acta oto-laryngologica. 2012 Jan;132(1):44-50