Objective:To investigate the role and molecular mechanism of death receptor 5 (DR5) in early brain injury (EBI) after subarachnoid hemorrhage (SAH), as well as the neuroprotective effect of soluble DR5 (sDR5) on SAH.Methods:Experiment 1: SD rats were randomly divided into sham-operated group ( n=6) and SAH group (SAH model was established by carotid artery puncture, n=30), and the SAH group was further subdivided into post-SAH (6 h) group, post-SAH (12 h) group, post-SAH (24 h) group, post-SAH (48 h) group and post-SAH (72 h) group ( n=6); Western blotting was used to detect the expressions of tumor necrosis factor (TNF)-α and DR5; immunofluorescent DR5 and neuronal nuclear antigen (NeuN) double staining was used to evaluate the DR5 expression in neurons. Experiment 2: SD rats were randomly divided into sham-operated group, SAH group, Trail group (injected Trail agonist dordaviprone), and Trail+sDR5 group (injected dordaviprone+sDR5, n=6); at the 24 th h of successfully constructed SAH model, the caspase family protein levels were detected by Western blotting, and Tunel staining and immunofluorescent DR5 and Caspase-3 double staining were performed. Experiment 3: SD rats were divided into sham-operated group, SAH group, Trail group and Trail+sDR5 group ( n=6); long-term motor functions, by modified Gracia score, forelimb placement experiment, rotarod test and misstep experiment, were evaluated 5, 7 and 12 d after successfully constructed SAH model; and long-term learning and memory functions were detected by water maze experiment 14, 16, 18, 20 and 21 d after successfully constructed SAH model. Results:(1) Result of Experiment 1: the expressions of TNF-α and DR5 in sham-operated group, post-SAH (6 h) group, post-SAH (12 h) group, post-SAH (24 h) group, post-SAH (48 h) group and post-SAH (72 h) group were statistically different ( F=837.992, P<0.001; F=503.942, P<0.001), and these expressions peaked 24 h after SAH; immunofluorescent DR5 and NeuN double staining showed that DR5 was located in neurons after SAH. (2) Result of Experiment 2: compared with the SAH group and Trail group, the Trail+sDR5 group had significantly decreased levels of activated caspase-8, tBid and activated caspase-3, significantly decreased numbers of Tunel positive cells and DR5 and activated caspase-3 co-marked positive cells ( P<0.05). (3) Result of Experiment 3: compared with the SAH group and Trail group, the Trail+sDR5 group had significantly increased Garcia scores, decreased failure rate in forelimb placement experiment, prolonged duration of stick rotation, and decreased foot fault rate ( P<0.05), suggesting that sDR5 could improve the long-term motor function deficit after SAH; water maze experiment showed that 21 d after SAH, compared with the SAH group and Trail group, Trail+sDR5 group had significantly increased proportion of escape time in the original platform quadrat in total escape time and increased proportion of movement path in the original platform quadrat in total movement path after platform removal ( P<0.05), suggesting that sDR5 could improve long-term learning and memory impairment after SAH. Conclusion:The sDR5 can inhibit DR5-Trail-mediated neuronal apoptosis and improve long-term neurological functional deficits after SAH.