Brain gamma-aminobutyrate aminotransferase (GABA-T) and monoamine oxidase (MAO) in patients with Alzheimer's disease.

Activities of Gamma-aminobutyrate aminotransferase (GABA-T) and Monoamine oxidase (MAO)-A and -B were estimated in postmortem brains from 6 control subjects without psychiatric or neurologic disorders and 8 histopathologically verified cases of patients with Alzheimer's disease and senile dementia of Alzheimer type (AD/SDAT). The enzyme activities were examined in four cortical brain regions, three nuclei in the basal ganglia, thalamus and white matter. GABA-T activities in the cortical regions (frontal, parietal, occipital and temporal cortices) and nucleus caudatus were significantly lowered in the AD/SDAT patients. The MAO-A activities were significantly increased in the occipital cortex, caudate nucleus, thalamus and white matter in the AD/SDAT patients. No significant differences were found in the other regions (frontal cortex, parietal cortex, temporal cortex, putamen and globus pallidus). The MAO-B activities in three cortical regions (frontal, parietal and occipital cortices), thalamus and white matter were significantly increased in the AD/SDAT patients, whereas no difference was apparent in the other regions. The changed activities could not be correlated with age or postmortem time. The present results are the first describing decreased GABA-T activities as well as increased MAO-A activities in brain from patients with AD/SDAT, while the results with MAO-B support previous findings. A possible connection was found between the order of magnitude of the changes in enzyme activities and the severity of the disease.