Dantrolene is cytoprotective in two models of neuronal cell death

The neuroprotective effects of dantrolene, an inhibitor of calcium release from intracellular stores, were investigated in a model of cell death induced by calcium release from endoplasmic reticulum in vitro. Thapsigargin (50 nM), a selective inhibitor of endoplasmic reticular Ca(2+)-ATPase, significantly increased the cytosolic Ca2+ concentration to 230% over basal levels, induced DNA fragmentation, and reduced cell viability from 94% in control cells to 41% after a 24-h treatment in GT1-7 hypothalamic neurosecretory cells. Pretreatment with dantrolene for 30 min significantly inhibited elevation of cytosolic Ca2+ levels, DNA fragmentation, and GT1-7 cell death induced by thapsigargin in a dose-dependent manner. To determine if dantrolene would also be protective in an in vivo model of neurodegeneration, it was administered intravenously immediately following a 5-min global cerebral ischemia in gerbils, and the number of intact hippocampal CA1 pyramidal neurons was counted 7 days later. The effects of dantrolene on brain and rectal temperature were monitored in a separate experiment. Dantrolene significantly increased the number of intact CA1 pyramidal neurons from 40% (untreated ischemic animals) to 67 (10 mg/kg), 78 (25 mg/kg), or 83% (50 mg/kg) of values in sham controls (all p < 0.001). No significant changes in brain or rectal temperature were detected for 4 h following 50 mg/kg dantrolene. These results suggest that abnormal Ca2+ release from intracellular stores can induce neuronal death and that such a mechanism may contribute to delayed hippocampal neuronal death after cerebral ischemia. Dantrolene may be a potentially useful drug for neuroprotection after cerebral ischemia.