DETERMINANTS OF THE STIMULATORY OPIOID EFFECT ON INTRACELLULAR CALCIUM IN SK-N-SH AND NG108-15 NEUROBLASTOMA

The opiate agonist etorphine elevated [Ca2+](i) in two neuroblastoma c ell lines. Fura-2 imaging of single cells revealed a small and variabl e calcium elevation in only 20% of cultures. Three factors were found to increase the probability (up to 70%) and the amplitude of the respo nse to etorphine: (a) synchronization of the cultures; (b) differentia tion of the cells; and (c) synergism with other stimulatory agents (ca rbachol in SK-N-SH and bradykinin in NG108-15 cells). The establishmen t of a reproducible experimental protocol may facilitate the study of the molecular mechanism(s) underlying the stimulatory activity of opia tes.