Biphasic effects of chlorpromazine on cell viability in a neuroblastoma cell line.

Although chlorpromazine was shown to greatly inhibit a Ca2+-mediated cell death at favorable concentrations (10(-6)-10(-5) M), it caused a drastic decrease in cell viability at higher concentrations (10(-4)-10(-3) M) in a human neuroblastoma cell line. The toxic effect of chlorpromazine also occurred in Ca2+-free medium and was not parallel to the amount of thiobarbituric acid-reactive substances produced. These results indicate that chlorpromazine has biphasic effects on cell viability according to the concentrations added, i.e. a protective effect against cell damage caused by Ca2+, and a direct toxic effect independent of extracellular Ca2+ or of lipid peroxidation.