Cell Membrane Expansion and Blockade of Action Potentials Produced by 2-decenoic Acid in Cultured Dorsal Root Ganglion Neurons

2-Decenoic acid, a fatty acid having 10 carbon atoms, blocks the action potentials of cultured dorsal root ganglion (DRG) neurons and this effect of 2-decenoic acid is reversible. From the analysis of the video pictures from Nomarski optics, relative values of the diameter and the thickness of the neurons increased to 1.06 and 1.14, respectively, when 2.1 mM 2-decenoic acid was applied to the neurons. The relative value of cell surface area, which was calculated from the equation for a spheroid, increased to about 1.20. On the other hand, relative fluorescence intensity of the fluorescent probe F18 (5-(octadecylthiocarbamoylamino)fluorescein) labeled neurons decreased to 0.81, when 2.1 mM 2-decenoic acid was applied to the neurons. This indicates that the relative cell surface area increased to 1.23, a value similar to that calculated from the results of the measurement of cell size. The time course of blocking action potentials after treatment of the fatty acid was similar to that of the cell membrane expansion. These results show that the fatty acid perturbs the cell membrane and expands the cell surface area and this expansion might reduce the opening ability of the Na+-channels in the membrane.