Neuroscience letters
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The effects of capsaicin were investigated on different populations of dorsal root ganglion cells in the in vitro mouse spinal cord-dorsal root ganglion preparation using intracellular electrodes. Dorsal root ganglion cells were characterised by the conduction velocity of their propagated action potential evoked by electrical stimulation of the dorsal root, and by the shape of their action potential. All cells with C-fiber characteristics (conduction velocity < 0.6 m/s; broad action potential with shoulder on the descending slope) were depolarised and generated action potentials when capsaicin (100-700 nM) was added to the bathing solution for 30 s. ⋯ Passive depolarization of the membrane by intrasomal current injection mimicked the conduction block in neurons with large myelinated fibers. These observations confirm that capsaicin applied directly to the dorsal root ganglion affects, in a dose-dependent manner, both myelinated and unmyelinated primary afferents with a higher potency for C-neurons. Capsaicin evoked action potentials in C-neurons but not in neurons with myelinated fibers.(ABSTRACT TRUNCATED AT 250 WORDS)