Death of Rat Sympathetic Ganglion Cells In Vitro Caused by Neurite Transection: Effect of Extracellular Calcium

Abstract

Calcium entry into neurons secondary to excitotoxic insults is believed to cause neuronal death after trauma and ischemia, but the role of calcium influx in neuronal death after neurite transection independent of excitotoxicity has not been clearly defined. This study assesses the effect of variations 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 transected with a custom-made injury device, and cell death was assessed with propidium iodide and fluorescence microscopy. We found that neurite transection caused a significant increase (p < 0.05) in cell death at all [Ca²⁺]_e studies, but there was no significant difference in mortality at the various [Ca²⁺]_e. Cell death significantly increased between 2 and 24 h postinjury at all three [Ca²⁺]_e. Cell death increased with decreasing distance between the cell body and the transection site, and there was a significant decrease in mortality at distances greater than 0.66 mm, irrespective of the [Ca²⁺]_e. These results suggest that influx of extracellular calcium is not responsible for posttransection cell death, suggesting that calcium release from internal stores or calcium-independent cell death mechanisms are triggered by neurite transection.