Venus-GABA_ARα1 localizes specifically to inhibitory synapses.

<p>(A) Light microscopy of fixed saggital sections from wild type and Otx1-VGABA_ARα1 transgenic mice treated with anti-GFP antibody and revealed with the DAB procedure. Transgenic, but not wild type mice express the fusion protein in layer 5/6 cortical pyramidal neurons. The fusion protein localizes to cell bodies (arrows) and processes (arrowheads) in cortex. Scale bars: 200 µm. (B) Immuno-electron microscopy shows VGABA_ARα1 expression (arrows) exclusively at inhibitory synapses by silver-intensified immunogold labeling (SIG). Inhibitory terminals immunoreactive for GAD65/67 are revealed with the DAB procedure (white asterisks). Asymmetric synapses (black asterisks) are immunonegative for both GAD and VGABA_ARα1. Scale: 500 nm. Cy: cytoplasm. Nu: nucleus. De: dendrite. V: Venus. G_AR: GABA_A receptor. (C) Within a total cortical area of 614.6 square microns 67 of the 134 inhibitory (symmetric) synapses were labeled by VGABA_ARα1, whereas none of the 200 excitatory (asymmetric) synapses were immunopositive for the fusion protein. (D) An average of 54% of inhibitory synapses were immunopositive for VGABA_ARα1, compared to 0% of the excitatory synapses. The data are presented as average ± SEM (t test).