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KMID : 0892920120210020075
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Experimental Neurobiology
2012 Volume.21 No. 2 p.75 ~ p.82
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Capsaicin Blocks the Hyperpolarization-Activated Inward Currents via TRPV1 in the Rat Dorsal Root Ganglion Neurons
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Kwak Ji-Yeon
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Abstract
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Capsaicin, the pungent ingredient in hot pepper, activates nociceptors to produce pain and inflammation. However, prolonged exposures of capsaicin will cause desensitization to nociceptive stimuli. Hyperpolarization-activated cation currents (Ih) contribute to the maintenance of the resting membrane potential and excitability of neurons. In the cultured dorsal root ganglion (DRG) neurons, we investigated mechanisms underlying capsaicin-mediated modulation of Ih using patch clamp recordings. Capsaicin (1 μM) inhibited Ih only in the capsaicin-sensitive neurons. The capsaicin-induced inhibition of Ih was prevented by preexposing the TRPV1 antagonist, capsazepine (CPZ). Capsaicin-induced inhibition of Ih was dose dependent (IC50= 0.68 μM) and partially abolished by intracellular BAPTA and cyclosporin A, specific calcineurin inhibitor. In summary, the inhibitory effects of capsaicin on Ih are mediated by activation of TRPV1 and Ca2+-triggered cellular responses. Analgesic effects of capsaicin have been thought to be related to desensitization of nociceptive neurons due to depletion of pain-related substances. In addition, capsaicin-induced inhibition of Ih is likely to be important in understanding the analgesic mechanism of capsaicin.
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KEYWORD
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capsaicin, DRG neuron, hyperpolarization-activated cation current, rat
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