Fig. 5.

IDE regulates CGRP_1–37 in vivo. (A) IDE^+/+ and IDE^−/− mice were treated with vehicle or capsaicin, and absolute endogenous CGRP levels were measured by IDMS²⁹ using a synthetic d18-CGRP_1–37 internal standard. CGRP_1–37 levels were significantly higher in the IDE^−/− mice than in the IDE^+/+ mice under both treatment conditions. (B) A unique model for CGRP regulation includes the IDE-mediated proteolysis pathway discovered here. (**P value < 0.01; P values were derived from the two-tailed Student t test, n = 3. Error bars show SEM.)