Nevertheless, only a few previous studies have explored certain markers of the tryptophan-serotonin (5-HT)-kynurenine (TSK) axis 24 h after brain ischemia (3, 5), and there are no prospective studies that have measured TSK axis markers in blood and urine in the hyperacute phase (<4.5 h) of brain ischemia. The gene discussed is TSKU; the disease is brain ischemia.