Quantitative autoradiography of hippocampal GABAB and GABAA receptor changes in Alzheimer's disease

GABAB and GABAA receptors were examined by quantitative [3H]GABA autoradiography in postmortem human hippocampus from 6 histopathologically verified cases of dementia of the Alzheimer type (DAT) and 6 normal controls. Significant decrements in the Bmax for both types of GABA receptors were observed in DAT hippocampus as compared to normal controls. No significant differences in Kd values were revealed. As compared to controls, DAT hippocampus exhibited fewer GABAB receptors in stratum moleculare of the dentate gyrus, stratum lacunosum-moleculare and stratum pyramidale of CA1. Significant loss of GABAA receptors in DAT hippocampus was also observed in the CA1 pyramidal cell region. These changes could not be correlated with differences in age nor in postmortem delay between the two groups. These findings may reflect the neuronal pathologies in CA1 region, in dentate gyrus, and in projections from the entorhinal cortex which are associated with the memory impairment in DAT.