I-menthol-induced [Ca2+](i) increase and impulses in cultured sensory neurons

We investigated the effects of l-menthol on cultured dorsal root ganglion ( DRG) cells, instead of free nerve endings of sensory fibers. Using Fura-2 m icrofluorimetry, we identified a few DRG neurons that showed an increase in intracellular free Ca2+ concentration ([Ca2+](i)) in response to l-menthol . They made up only 10% of the neurons activated by a high K+ solution. l-M enthol induced the [Ca2+](i) increase in a dose-dependent manner, with an E C50 of 37.9 mu M and a Hill coefficient of 0.97. A related compound, cycloh exanol, had no effect. When extracellular Ca2+ was removed, l-menthol did n ot induce the [Ca2+](i) increase. Whole-cell current-clamp recordings revea led that l-menthol induced depolarization (13.2 mV, receptor potential) lea ding to impulses. We conclude that l-menthol induced the impulses through a ctivation of menthol receptors in a small subset of the cultured sensory ne urons. NeuroReport 11:2151-2155 (C) 2000 Lippincott Williams & Wilkins.