Fig. 8. Inhibition of varicosity formation aggravates NMDA-induced neuronal death. (A) Representative confocal images of PI fluorescence in hippocampal slices 24 hours after 10 minutes exposure to 3 µM (a,b) or 30 µM (c,d) NMDA in normal (a,c) or low Na⁺ conditions (b,d). Culture medium was changed to normal or low Na⁺ buffer 30 minutes prior to NMDA treatment. (e) PI fluorescence intensity was quantified in the CA1 region (solid columns), the CA3 region (hatched columns) and the DG (open columns). Low Na⁺ conditions exacerbated NMDA excitotoxicity; NMDA in low Na⁺ solution evoked neuronal death all over the hippocampus. Note that treatment with NMDA even at a concentration of 3 µM showed apparent neurotoxicity. (B) Slices were treated with a mixture of protease inhibitors (1:1000) for 12 hours and exposed to 3 or 30 µM NMDA. They were subsequently incubated in normal medium at 37°C for 24 hours and PI uptake was measured. Treatment with protease inhibitors exacerbated NMDA-induced neuronal death. **P<0.01 versus Control, ^#P< 0.05, ^##P<0.01 versus corresponding concentrations of NMDA. Data are the means±s.e.m. of 9-12 slices.