Anti-GluR3 selectively destroys astrocytes after 4 hr exposure. Mixed cultures exposed to vehicle or various antisera for 4 hr were incubated with propidium iodide (PI) for 30 min, fixed, and immunostained for GFAP or MAP-2. In cultures incubated with anti-GluR3 (1 mg/ml), approximately half the astrocytes (left) display a deranged morphology characterized by swelling, fragmentation, and lysis (red arrows). Binucleated astrocytes are a common feature (double red arrows). Other neighboring astrocytes appear morphologically normal (green arrow). Only deranged astrocytes are propidium iodide-positive, indicating damage to the plasma membrane occurring presumably as the cell begins to die (red nuclei). In contrast, most neurons appear morphologically normal and propidium iodide-negative at this time point (right, green arrows). The red arrowhead marks a propidium iodide-positive nucleus, possibly a dying astrocyte unlabeled by the MAP-2 antibody. Both astrocytes and neurons were comparatively unperturbed in vehicle-treated cultures (data not shown). The images presented are representative of seven experiments. Scale bar, 50 μm (pertains to this and all subsequent images).