7B, https://links.lww.com/ALN/D247); while the levels of the downstream neuroprotective metabolite kynurenic acid did not change significantly after cardiac arrest ([kynurenic acid] in naïve IDO−/−versus IDO−/−+ l-kynurenine mice 30 min postresuscitation: 4.37 ± 1 ng/mL versus 2,147 ± 2,928 ng/mL; P = 0.247, n = 4 to 8/group; supplemental fig. The gene discussed is IDO1; the disease is cardiac arrest.