BLOCKING CA2-RAT DRG NEURONS( MOBILIZATION WITH THAPSIGARGIN REDUCES NEURITE INITIATION IN CULTURED ADULT)

Adult rat DRG neurons rapidly extend extensive neuritic arbors after a 1-2-day delay in culture and generate large depolarization-induced ca lcium signals during this time period that are derived primarily from intracellular calcium release. To assess whether intracellular calcium mobilization is required for neurite initiation, calcium stores were depleted by brief exposure to the irreversible endoplasmic reticulum c alcium ATPase inhibitor thapsigargin; cultures were then maintained fo r 3 days, immunostained for neurofilament and scored for percentage of neurons with neurites at least twice as long as the cell body. Brief thapsigargin treatment (20 min) during the first 24 h in culture resul ted in a substantial decrease in neurite initiation frequency without affecting neuronal or nonneuronal cell survival, suggesting that intra cellular calcium mobilization is necessary for triggering neurite init iation in these neurons.