The Effects of Local and Intravenous Anesthetics on Recombinant Rat VR1 Vanilloid Receptors

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Abstract
MM; 10 mM represents 0.25%–0.27% wt/vol) or IV anesthetics (propofol 10 μM, thiopental 100 μM, and ketamine 100 μM) interact with recombinant rat VR1 expressed in human embryonic kidney (HEK293) cells (VR1-HEK293). We have assessed receptor interaction functionally by monitoring intracellular Ca2+ ([Ca2+]i) in Fura2-loaded cells at 37°C. The addition of capsaicin (60 nM) produced a time-dependent biphasic increase in [Ca2+]i amounting to 50–100 nM above than basal, which was inhibited by capsazepine 10 μM and was absent in wild type HEK293 cells. Lidocaine and prilocaine alone (e.g., at 10 mM) significantly increased [Ca2+]i by 67 ± 6 nM and 33 ± 7 nM, respectively, and concentration-dependently inhibited the capsaicin response. The effects of procaine were obscured by anesthetic-induced quenching of Fura2. In wild type HEK293 cells, lidocaine (10 mM) alone produced a small increase in [Ca2+]i. All IV anesthetics failed to modify capsaicin-increased [Ca2+]i. In conclusion, the present data suggest that local but not IV general anesthetics interact with recombinant rat VR1 receptors with the former anesthetics having antagonistic activity. IMPLICATIONS: Vanilloid receptors (VR1) are activated by capsaicin, the pain-producing component of hot chili peppers. We suggest that local (but not IV general) anesthetics may have inhibitory actions on this receptor....