IDO2 and cardiac arrest: Brain magnetic resonance imaging with diffusion-weighted imaging revealed restriction of water diffusivity 24 h after cardiac arrest in wild-type mice; indoleamine 2,3-dioxygenase deletion prevented water diffusion abnormalities, which was reverted in IDO−/− mice receiving l-kynurenine (apparent diffusion coefficient, μm2/ms: wild-type, 0.48 ± 0.07; IDO−/−, 0.59 ± 0.02; IDO−/− and l-kynurenine, 0.47 ± 0.08; P = 0.007, n = 6).