l-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 microfluorimetry, 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-Menthol induced the [Ca2+]i increase in a dose-dependent manner, with an EC50 of 37.9 microM and a Hill coefficient of 0.97. A related compound, cyclohexanol, had no effect. When extracellular Ca2+ was removed, l-menthol did not induce the [Ca2+]i increase. Whole-cell current-clamp recordings revealed that l-menthol induced depolarization (13.2 mV, receptor potential) leading to impulses. We conclude that l-menthol induced the impulses through activation of menthol receptors in a small subset of the cultured sensory neurons.
Department of Intelligence Science and Technology, Graduate School of Informatics, Kyoto University, Japan.
M
M
Okazawa
T
T
Terauchi
T
T
Shiraki
K
K
Matsumura
S
S
Kobayashi
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005727:Ganglia, Spinal / Q000166:cytology / Q000502:physiology; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008610:Menthol / Q000494:pharmacology*; D009475:Neurons, Afferent / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
D008610:Menthol; D011188:Potassium; D002118:Calcium