In humans, aging is accompanied by the deterioration of the hearing function--presbycusis. The major etiology for presbycusis is the loss of hair cells in the inner ear; less well known are changes in the central auditory system. Therefore, we used 1H magnetic resonance spectroscopy at 3T tomograph to examine metabolite levels in the auditory cortex of three groups of subjects: young healthy subjects less than 30 years old and subjects older than 65 years either with mild presbycusis corresponding to their age or with expressed presbycusis. Hearing function in all subjects was examined by pure tone audiometry (125-16,000 Hz). Significant differences were found in the concentrations of glutamate and N-acetylaspartate, with lower levels in aged subjects. Lactate was particularly increased in subjects with expressed presbycusis. Significant differences were not found in other metabolites, including GABA, between young and elderly subjects. The results demonstrate that the age-related changes of the inner ear are accompanied by a decrease in the excitatory neurotransmitter glutamate as well as a lactate increase in the auditory cortex that is more expressed in elderly subjects with large hearing threshold shifts.

• MeSH
• audiometrie čistými tóny MeSH
• dospělí MeSH
• glutamáty metabolismus   MeSH
• kyselina asparagová analogy a deriváty   metabolismus   MeSH
• laktáty metabolismus   MeSH
• lidé MeSH
• magnetická rezonanční spektroskopie * MeSH
• presbyakuze metabolismus   MeSH
• senioři MeSH
• sluchové korové centrum metabolismus   MeSH
• stárnutí metabolismus   MeSH
• studie případů a kontrol MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH

Changes in the levels of gamma-aminobutyric acid (GABA) are known to occur in different parts of the brain during aging. In our study we attempted to define the effect that aging has on glutamate decarboxylase (GAD), the key enzyme in the synthesis of GABA, in the central parts of the auditory system. Age-related changes in GAD65 and GAD67 levels were investigated using immunohistochemistry and Western blotting in the inferior colliculus (IC), the auditory cortex (AC) and the visual cortex in Long-Evans rats. The results show that aging is associated with a decrease in the numbers of GAD65- and 67-immunoreactive neurons and the optical density of their somas in both the IC and AC. Western blot analysis revealed a pronounced age-related decline in the levels of GAD65 and 67 proteins in both the IC and AC. For comparison, in the visual cortex the decrease in both proteins was less pronounced than in the IC and AC. A similar pattern of age-related changes was found in Fischer 344 rats, a strain that manifests a rapid loss of hearing function with aging. The observed age-related decline in the levels of GAD65 and 67 may contribute significantly to the deterioration of hearing function that accompanies aging in mammals, including man.

• MeSH
• analýza rozptylu MeSH
• colliculus inferior metabolismus   MeSH
• druhová specificita MeSH
• GABA fyziologie   metabolismus   MeSH
• glutamát dekarboxyláza metabolismus   MeSH
• krysa rodu rattus MeSH
• lidé MeSH
• potkani inbrední F344 MeSH
• potkani Long-Evans MeSH
• presbyakuze metabolismus   MeSH
• protein - isoformy analýza   metabolismus   MeSH
• sluchové korové centrum metabolismus   MeSH
• stárnutí metabolismus   MeSH
• western blotting metody   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• lidé MeSH
• zvířata MeSH
• Publikační typ
• práce podpořená grantem MeSH