Death of rat sympathetic ganglion cells in vitro caused by neurite transection: Effect of extracellular calcium

Calcium entry into neurons secondary to excitotoxic insults is believed to cause neuronal death after trauma and ischemia, but the role of calcium inf lux in neuronal death after neurite transection independent of excitotoxici ty has not been clearly defined. This study assesses the effect of variatio ns in extracellular calcium concentration ([Ca2+](e)) from 50 nM to 5 mM on cell death, in 14-day-old cultures of dissociated sympathetic neurons from the superior cervical ganglia of newborn rats. The neurites were transecte d with a custom-made injury device, and cell death was assessed with propid ium iodide and fluorescence microscopy. We found that neurite transection c aused a significant increase (p < 0.05) in cell death at all [Ca2+](e) stud ies, but there was no significant difference in mortality at the various [C a2+](e). Cell death significantly increased between 2 and 24 h postinjury a t all three [Ca2+](e). Cell death increased with decreasing distance betwee n the cell body and the transection site, and there was a significant decre ase in mortality at distances greater than 0.66 mm, irrespective of the [Ca 2+](e). These results suggest that influx of extracellular calcium is not r esponsible for posttransection cell death, suggesting that calcium release from internal stores or calcium-independent cell death mechanisms are trigg ered by neurite transection.