Glutamate-induced toxicity in rat primary cortical cells as assessed by phase contrast microscopy (100×). Primary cortical cells isolated from 19 day old fetal rat brains were cultured for 7 days and then treated with 1 mM glutamate alone or in the presence of estrogens for 6 h. Degenerated cells are depicted by arrowheads. A = untreated control cells; B = cells treated with 1 mM glutamate for 6 h; C = cells treated with 1 mM glutamate and 1 μM 17β-E2; D = cells treated with 1 mM glutamate and 1 μM Δ8, 17β-E2. Note after glutamate treatment, dead cells with loss of dendrites are clearly visible in the cultures. In contrast, either untreated control cells or cells treated with glutamate in presence of estrogens retain their normal morphology. Dendrites and membranes are clearly visible and only a few degenerated cells are present in these cultures (A,C,D).