Effects of capsaicin on Ca2+ release from the intracellular Ca2+ stores in the dorsal root ganglion cells of adult rats

초록

We have investigated the effect of capsaicin on Ca2+ release from the intracellular calcium stores. Intracellular calcium concentration ([Ca2+]<inf>i</inf>) was measured in rat dorsal root ganglion (DRG) neurons using microfluorimetry with fura-2 indicator. Brief application of capsaicin (1 μM) elevated [Ca2+]<inf>i</inf> in Ca2+-free solution. Capsaicin-induced [Ca2+]<inf>i</inf> transient in Ca2+-free solution was evoked in a dose-dependent manner. Resiniferatoxin, an analogue of capsaicin, also raised [Ca2+]<inf>i</inf> in Ca2+-free solution. Capsazepine, an antagonist of capsaicin receptor, completely blocked the capsaicin-induced [Ca2+]<inf>i</inf> transient. Caffeine completely abolished capsaicin-induced [Ca2+]<inf>i</inf> transient. Dantrolene sodium and ruthenium red, antagonists of the ryanodine receptor, blocked the effect of capsaicin on [Ca2+]<inf>i</inf>. However, capsaicin-induced [Ca2+]<inf>i</inf> transient was not affected by 2-APB, a membrane-permeable IP<inf>3</inf> receptor antagonist. Furthermore, depletion of IP<inf>3</inf>-sensitive Ca2+ stores by bradykinin and phospholipase C inhibitors, neomycin, and U-73122, did not block capsaicin-induced [Ca2+]<inf>i</inf> transient. In conclusion, capsaicin increases [Ca2+]<inf>i</inf> through Ca2+ release from ryanodine-sensitive Ca2+ stores, but not from IP<inf>3</inf>-sensitive Ca2+ stores in addition to Ca2+ entry through capsaicin-activated nonselective cation channel in rat DRG neurons. © 2001 Academic Press.

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