DUAL EFFECTS OF OPIOIDS ON TRANSMITTER RELEASE, INTRACELLULAR CALCIUMAND CALCIUM-UPTAKE IN SK-N-SH CELL-LINE

The effect of opiates on KCl-induced neurotransmitter release (preload ed [H-3] norepinephrine), intracellular calcium level (fura 2) and cal cium influx (Ca-45(++) uptake) was measured in the human neuroblastoma SK-N-SH. Opiates exerted either inhibition or augmentation of transmi tter release, both effects were blocked by naloxone. Similarly, opiate s either reduced or potentiated KCl-induced elevation in cytosolic [Ca ++], with neighboring cells responding oppositely. The stimulatory eff ect of opiates on cytosolic calcium was dependent on the presence of e xtracellular calcium ions. Opiates stimulated calcium uptake by SK-N-S H cells. This stimulation was blocked by naloxone but was not prevente d by pretreating the cells with pertusis toxin.