LAUSR

Gamma‐aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the central nervous system. GABA type A receptors (GABAARs) are severely affected in Alzheimer's disease (AD). However, the distribution and subunit composition of GABAARs in the AD brain are not well understood. This is the first comprehensive study to show brain region‐ and cell layer‐specific alterations in the expression of the GABAAR subunits α1‐3, α5, β1‐3 and γ2 in the human AD hippocampus, entorhinal cortex and superior temporal gyrus. In late‐stage AD tissue samples using immunohistochemistry we found significant alteration of all investigated GABAARs subunits except for α3 and β1 that were well preserved. The most prominent changes include an increase in GABAAR α1 expression associated with AD in all layers of the CA3 region, in the stratum (str.) granulare and hilus of the dentate gyrus. We found a significant increase in GABAAR α2 expression in the str. oriens of the CA1‐3, str. radiatum of the CA2,3 and decrease in the str. pyramidale of the CA1 region in AD cases. In AD there was a significant increase in GABAAR α5 subunit expression in str. pyramidale, str. oriens of the CA1 region and decrease in the superior temporal gyrus. We also found a significant decrease in the GABAAR β3 subunit immunoreactivity in the str. oriens of the CA2, str. granulare and str. moleculare of the dentate gyrus. In conclusion, these findings indicate that the expression of the GABAAR subunits shows brain region‐ and layer‐specific alterations in AD, and these changes could significantly influence and alter GABAAR function in the disease.