Primary cortical neuron viability is reduced by expression of capn-InsP3R1. Rat primary cortical cultures were transduced with adeno-associated virus 2/1 expressing lacZ, capn-InsP3R1 D2550A, or capn-InsP3R1 (7 DIV). (a) One week following transduction (14 DIV), cultures were stained for microtubule-associated protein 2 (MAP2) (red) and nuclei (blue; left panel), or incubated with calcein-AM (green) and propidium iodide (PI) (red; right panel). Representative 100· epifluorescence images captured for counting are shown. (b) Percent neuronal survival as determined by counts of MAP2-reactive cells (one-way ANOVA; *p < 0.001). (c) Percent cell survival as determined by counts of calcein-AM positive, PI-negative cells (unpaired t-tests with unequal variance; *p < 0.001). Expression of capn-InsP3R1 resulted in a significant decrease in percent viable neurons compared with lacZ and capn-InsP3R1 D2550A as determined by both assays.