Traumatic injury of cortical neurons causes changes in intracellular calcium stores and capacitative calcium influx

Using an in vitro traumatic injury model, we examined the effects of mechan ical (stretch) injury on intracellular Ca2+ store-mediated signaling in cul tured cortical neurons using fura-2. We previously found that elevation of [Ca2+](i) by the endoplasmic reticulum Ca2+-ATPase inhibitor, thapsigargin, was abolished 15 min post-injury. In the current studies, pre-injury inhib ition of phospholipase C with neomycin sulfate maintained Ca2+-replete stor es 15 min post-injury, suggesting that the initial injury-induced store dep letion may be due to increased inositol trisphosphate production. Thapsigar gin-stimulated elevation of [Ca2+], returned with time after injury and was potentiated at 3 h. Stimulation with thapsigargin in Ca2+-free media revea led that the size of the Ca2+ stores was normal at 3 h post-injury, However , Ca2+ influx triggered by depletion of intracellular Ca2+ stores (capacita tive Ca2+ influx) was enhanced 3 h after injury. Enhancement was blocked by inhibitors of cytosolic phospholipase A, and cytochrome P450 epoxygenase. Since intracellular Ca2+ store-mediated signaling plays an important role i n neuronal function, the observed changes may contribute to dysfunction pro duced by traumatic brain injury. Additionally, our results suggest that cap acitative Ca2+ influx may be mediated by both conformational coupling and a diffusible messenger synthesized by the combined action of cytosolic PLA, and P450.