MULTIPLE EFFECTS OF OPIATES ON INTRACELLULAR CALCIUM LEVEL AND ON CALCIUM-UPTAKE IN 3 NEURONAL CELL-LINES

The present study examines the modulation by opiates of intracellular calcium levels and calcium entry, using fura-2 imaging and Ca-45(2+) uptake, in three neuronal cell lines. We show that opiates (10(-7)-10(-5) M morphine and 10(-9)-10(-7) M etorphine) exert both inhibitory and excitatory effects on KCl-induced elevation in intracellular calcium level in SK-N-SH, NG108-15 and NMB cell lines. In addition, opiates elevate basal (non KCl-stimulated) intracellular calcium level in all three cell cultures. Ca-45(2+) uptake is augmented by opiates in SK-N-SH cells and this stimulatory effect is not blocked by pertussis toxin. In NMB cells, an additional inhibitory effect of opiates on basal calcium takes place: opiates reduce intracellular calcium level as measured by fura-2, and decrease calcium influx as detected by Ca-45(2+) uptake. The heterogeneity in the opioid regulation of calcium could not be attributed to the type of opioid drug, neither to its concentration nor to the experimental conditions, since neighboring cells within the same culture responded differently.