EFFECT OF HALOTHANE ON K-STIMULATED [H-3] NORADRENALINE RELEASE AND INCREASED [CA2+](I) IN SH-SY5Y HUMAN NEUROBLASTOMA-CELLS( AND CARBACHOL)

We have examined the effects of the volatile general anaesthetic agent , halothane, on K+ and carbachol stimulated [H-3]noradrenaline release and associated increases in intracellular Ca2+ in a cultured human ne uroblastoma cell line, SH-SY5Y. K+ (but not carbachol) stimulated [3H] noradrenaline release, and the increase in Ca2+ concentration was enti rely Ca2+ dependent. Halothane produced a dose-dependent reduction in K+ evoked release of [H-3]noradrenaline with significant inhibition (1 7%) occurring from 1.26 atm%. Basal and carbachol evoked release were unaffected. Halothane also produced a dose-dependent reduction in K+ e voked increases (measured at the peak) in intracellular Ca2+ with sign ificant inhibition (29%) occurring from 0.88 atm%. K+ plateau, basal a nd carbachol evoked increases in intracellular Ca2+ were unaffected. T hese data suggest that halothane reduced Ca2+ entry through voltage-se nsitive Ca2+ channels and implicate this important class of ion channe l in the mechanism of anaesthesia.