GABAA receptors are the major inhibitory receptors in the brain. They are hetero-pentamers with a composition of predominantly two α, two β and one γ or δ subunit. From the six α subunit genes, the α5 subunit displays a limited spatial expression pattern and is known to mediate both phasic and tonic inhibition. In this study, using immunoaffinity-based proteomics we identified the α5 subunit containing receptor complexes in hippocampus and olfactory bulb. The α1-α5 interaction was identified in both brain regions albeit with significantly different stoichiometries. In line with this, reverse IPs using anti-α1 antibody showed the α5-α1 co-occurrence and validated the quantitative difference. In addition, we showed that the association of Neuroligin 2 with α1-containing receptors was much higher in olfactory bulb than hippocampus, which was confirmed using blue native gel electrophoresis and quantitative mass spectrometry. Finally, immunocytochemical staining revealed co-localization of α1 and α5 subunits in post-synaptic puncta in the hippocampus.