GABAA receptors: immunocytochemical distribution of 13 subunits in the adult rat brain
Section snippets
Animals and tissue preparation
Adult male Sprague–Dawley rats (250–350 g; Forschungsinstitut für Versuchstierzucht, Himberg, Austria) were injected with a lethal dose of thiopental (150 mg/kg, i.p.; Sanabo, Austria) and perfused through the ascending aorta with 50 ml phosphate-buffered saline (PBS; 50 mM phosphate buffer, pH 7.4, in 0.9% NaCl) followed by 200 ml 4% paraformaldehyde in PBS. The brains were postfixed in the same fixative for 90 min at 4°C, then transferred to 20% sucrose in PBS and kept there at 4°C for 24 h.
Results
In Fig. 1, Fig. 2, Fig. 3, the immunocytochemical distribution of 13 different GABAA receptor subunits is presented at three different sagittal levels. Details on the GABAA receptor subunit-like immunoreactivity (IR) in certain brain areas are depicted at higher magnifications of sagittal and coronal sections in Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11, Fig. 12, Fig. 13, Fig. 14, Fig. 15, Fig. 16, Fig. 17, Fig. 18, Fig. 19, Fig. 20. In Table 1, a qualitative and
Discussion
The present study provides, for the first time, a concomitant comprehensive analysis of the immunocytochemical distribution of 13 GABAA receptor subunits, α1–α6, β1–β3, γ1–γ3 and δ, in the rat brain. Our data are generally in good agreement with previous reports on the distribution of individual subunits in parts or in the entire rat brain, notably with the most extensive study by Fritschy and Mohler27 and those of other groups.9., 12., 20., 21., 22., 30., 32., 49., 60., 62., 85., 86., 103.
Conclusion
There is a conspicuous heterogeneity of individual GABAA receptor subunit-IR allowing for a huge variety of differently constituted GABAA receptor subtypes. In spite of this apparent complexity, general frameworks of receptor-IR can be recognized. The most widely distributed immunoreactivities are those for subunits α1 and γ2. These subunits are likely constituents of a high portion of GABAA receptors. Concomitantly, all three β-subunit-IRs are widely distributed in the brain. Their
Acknowledgements
We thank C. Trawöger for preparing the photographs. We thank Dr Z. Nusser for discussions. The work was supported by grants from the Austrian Science Foundation (P12159-med), the Austrian National Bank (6317, 7621) and a grant from the European Commission (ERBBIO4 CT960585).
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Present address: University Clinics for Neurosurgery, Währinger Gürtel 18–20, A-1090 Vienna, Austria.