GxTX-594 labels CA1 hippocampal pyramidal neurons transfected with Kv2.1-GFP. Two-photon excitation images of rat CA1 hippocampal pyramidal neurons in brain slices as in Fig. 9 A. Kv2.1-GFP (left), GxTX-594 (middle), and overlay (right). Scale bars, 10 μm in all panels. (A) Pyramidal neurons 2 d after transfection with Kv2.1-GFP. (B) Pyramidal neurons 4 d after transfection with Kv2.1-GFP. (C) Pyramidal neurons 6 d after transfection with Kv2.1-GFP.