Menthol blocks dihydropyridine‐insensitive Ca2+ channels and induces neurite outgrowth in human neuroblastoma cells

Abstract Voltage‐gated Ca 2+ channels were identified in LA‐N‐5 human neuroblastoma cells using the Ca 2+ sensitive fluorescent probe, fura‐2. Using a variety of “classical” Ca 2+ channel blockers, we have demonstrated the presence of both dihydropyridine (DHP)‐sensitive and ‐insensitive channel types that can be activated by depolarization of the cells with either high K + or gramicidin in the bathing solution. Brief exposure of LA‐N‐5 cells to menthol blunted the depolarization‐induced Ca 2+ influx though both DHP‐sensitive and DHP‐insensitive channels. This effect is concentration dependent (50% maximal blocking effect with 0.25 mM menthol), rapid in onset, and readily reversible. The specificity of the Ca 2+ ‐channel blocking effect of menthol was demonstrated in parallel studies using compounds with similar structures: menthone blocked Ca 2+ channels with about half the potency of menthol, while cyclohexanol was without effect. Addition of either menthol or menthone to LA‐N‐5 cultures induced neurite outgrowth, cellular clustering, and reduction of cell growth in a dose‐dependent fashion that correlated with the ability of these compounds to inhibit the DHP‐insensitive Ca 2+ influx. Cyclohexanol had no biologic activity. Taken together, the parallel potency for blockade of DHP‐insensitive Ca 2+ influx with the biologic activity of menthol suggests a role for certain types of Ca 2+ channels in triggering growth and morphologic changes in LA‐N‐5 cells.