Localization of the mouse α1A‐adrenergic receptor (AR) in the brain: α1AAR is expressed in neurons, GABAergic interneurons, and NG2 oligodendrocyte progenitors

α1-Adrenergic receptors (ARs) are not well defined in the central nervous system. The particular cell types and areas that express these receptors are uncertain because of the lack of high avidity antibodies and selective ligands. We have developed transgenic mice that either systemically overexpress the human α1A-AR subtype fused with the enhanced green fluorescent protein (EGFP) or express the EGFP protein alone under the control of the mouse α1A-AR promoter. We confirm our transgenic model against the α1A-AR knockout mouse, which expresses the LacZ gene in place of the coding region for the α1A-AR. By using these models, we have now determined cellular localization of the α1A-AR in the brain, at the protein level. The α1A-AR or the EGFP protein is expressed prominently in neuronal cells in the cerebral cortex, hippocampus, hypothalamus, midbrain, pontine olivary nuclei, trigeminal nuclei, cerebellum, and spinal cord. The types of neurons were diverse, and the α1A-AR colocalized with markers for glutamic acid decarboxylase (GAD), gamma-aminobutyric acid (GABA), and N-methyl-D-aspartate (NMDA) receptors. Recordings from α1A-AR EGFP-expressing cells in the stratum oriens of the hippocampal CA1 region confirmed that these cells were interneurons. We could not detect expression of the α1A-AR in mature astrocytes, oligodendrocytes, or cerebral blood vessels, but we could detect the α1A-AR in oligodendrocyte progenitors. We conclude that the α1A-AR is abundant in the brain, expressed in various types of neurons, and may regulate the function of oligodendrocyte progenitors, interneurons, GABA, and NMDA receptor containing neurons. J. Comp. Neurol. 497:209–222, 2006. © 2006 Wiley-Liss, Inc.