The distribution of 13 GABAA receptor subunit mRNAs in the rat brain. II. Olfactory bulb and cerebellum

Abstract

In an effort to determine subunit compositions of in vivo GABAA receptors, the cellular localization of 13 subunit encoding mRNAs (α,-α6, β,-βu γ2-γ3+~ δ) was determined in the rat olfactory bulb and cerebellum. Cerebellar granule cells expressed significant quantities of α α6, β2, β3, γ2, and 6δ mRNAs. They contained very much lower levels of α4, β and 73 mRNAs, and the αz, α3, α5, and γ, genes appeared to be silent. Purkinje cells contained only the α15 β2, β3, and γz mRNAs. Putative Bergmann glial cells were found to contain the γ1 mRNA and possibly the α2 mRNA. In the molecular layer, only the 1f 2 and y2 mRNAs were expressed in stellate/basket cells. The 3 probe hybridized weakly to targets in the molecular layer. The inferior olivary nucleus contained significant quantities of 2, a4, and y, transcripts, with the 1 3, 02, 03, and 72 mRNAs also present. In the olfactory bulb, mitral cells were found to express the a 0 2,03, and 72 mRNAs strongly and the a3 mRNA weakly. Tufted cells contained a a3, 2, 3, and y2 mRNAs and, occasionally, the a2 mRNA. In the internal granule cells the az, a4, as, 3, and 6 mRNAs were all present. Low levels of a3, y2, and 73 mRNAs were also noted in these cells. Periglomerular cells expressed low levels of a2, a3, 4, &, 3,7n 72 and 73 mRNAs. No ae mRNA was present in the olfactory bulb. Correlations that are general ones from other brain regions are the colocalizations of a A, A, and a4o mRNAs. In both the olfactory bulb and cerebellum, a,2y2 receptor cores are probably employed. The o-subunit mRNA appears to codistribute with a-subunit mRNAs (a4 and a6) associated with GABAA subunits that fail to bind benzodiazepine agonists.