Fig. 3. Excitotoxic challenge to primary cortical neuron cultures. 1Primary cortical neuron cultures were exposed to 300 μm NMDA without (A ) or with (B ) preincubation in 10 μm dexmedetomidine. Eight hours later, the cells were fixed and subjected to nuclear chromatin fluorescent staining. Nuclei with features suggestive of neuronal death (pycnosis, i.e. , chromatin condensation or fragmentation) were counted (arrowheads). Normal nuclei are shown (arrows). Scale bar = 20 μm.