Age-related hearing loss, presbyacusis, is becoming one of the most common health disabilities in elderly people. Despite intensive research, age-related changes are still poorly understood and, given the continuous aging of the population, it is desirable to improve our knowledge of the mechanisms of presbyacusis. Consequently we decided to study age-related changes that appear in the structure and function of the central auditory system in the brain of experimental animals. In the first experiment we tested the hypothesis that during aging there is substantial decline of GABA-mediated inhibition in the central auditory system of the rat. We evaluated levels of both isoforms of glutamatedecarboxylase (GAD65, GAD67), a key enzyme in GABA synthesis. Western blot analysis revealed an overall decrease in levels of both isoforms in the inferior colliculus as well as the auditory cortex in aged rats. The same pattern was found when we used immunohistochemistry analysis; there was a decrease in the number of GAD65 and GAD67-ir neuronal bodies and a decrease in the density of the labeling. The results were similar for both GAD isoforms and both studied strains - the normally aging Long Evans strain (LE) and the Fischer 344 (F344) strain known for accelerated aging. In the next experiment we evaluated..
