title: The expression of glutamate aspartate transporter (GLAST) within the human cochlea and its distribution in various patient populations.
abstract: Glutamate plays an important role in the central nervous system as an excitatory neurotransmitter. However, its abundance can lead to excitotoxicity which necessitates the proper function of active glutamate transporters. The glutamate-aspartate transporter (GLAST) has been shown to exist and function within non-human cochlear specimens regulating the inner ear glutamate concentration. In this study, we examined human cochleas from formalin-fixed celloidin-embedded temporal bone specimens of three different types of patients (Meniere's disease, normal controls, and other otopathologic conditions) and examined the differential expression of GLAST in the spiral ligament of the basal, middle, and apical turns of the cochlea. Immunohistochemical staining was performed with polyclonal antibodies against GLAST and image analysis was carried out with the Image J analysis software. In contrast to other studies with non-human specimens, GLAST was expressed in the spiral ligament fibrocytes but was not detected in the satellite cells of the spiral ganglia or supporting cells of the Organ of Corti in the human cochlea. Our data also showed that GLAST expression significantly differs in the basal and apical turns of the cochlea. Lastly, post-hoc analysis showed a difference in the GLAST immunoreactive area of patients with Meniere's disease when compared to that of patients with other otopathologic conditions-such as presbycusis or ototoxicity. These results may potentially lead to further understanding of different disease states that affect hearing.
authors.affiliation: Department of Head and Neck Surgery, David Geffen School of Medicine, University of California, Los Angeles, CA 90095-1624, USA.
authors.forename: Sameer
authors.initials: S
authors.lastname: Ahmed
authors.forename: Nopawan
authors.initials: N
authors.lastname: Vorasubin
authors.forename: Ivan A
authors.initials: IA
authors.lastname: Lopez
authors.forename: Seiji
authors.initials: S
authors.lastname: Hosokawa
authors.forename: Gail
authors.initials: G
authors.lastname: Ishiyama
authors.forename: Akira
authors.initials: A
authors.lastname: Ishiyama
mesh_terms: D000368:Aged; D027322:Amino Acid Transport System X-AG / Q000378:metabolism*; D000704:Analysis of Variance; D001706:Biopsy; D003051:Cochlea / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D008575:Meniere Disease / Q000473:pathology*; D013136:Spiral Ganglion / Q000378:metabolism / Q000473:pathology; D013701:Temporal Bone / Q000378:metabolism / Q000473:pathology; D014725:Vestibular Nerve / Q000378:metabolism / Q000473:pathology
chemical_list: D027322:Amino Acid Transport System X-AG
keywords: Glutamate; Glutamate-aspartate transporter; Hearing loss; Human temporal bone; Immunohistochemistry; Meniere's disease