Objective To investigate the effects of omega-3 polyunsaturated fatty acids (ω-3 PUFA)supplementation on brain edema,autophagy response and neurobehavioral outcome after traumatic brain injury (TBI) in rats and the related mechanisms.Methods TBI rat models were established using Feeney's method.Seventy-two SD rats were divided into 4 groups using random number table:sham operation group,TBI group,ω-3 PUFA supplementation group (TBI + ω-3 group) and autophagy inhibitor 3-methyladenine group (TBI + 3-MA group) (all n =18),each group was further divided into 3 sub-groups (n =6) corresponding to 3 time points (days 1,3,and 7 after TBI).On each of the 3 time points,we measured rat behavioral outcomes with modified neurologic severity score (mNSS) tests;brain water content was measured with wet-dry weight method.The mRNA and protein expressions of autophagy-related factors (LC3-Ⅱ and Beclin-1) in TBI cerebral cortex were determined by immunohistochemistry staining,reverse transcription-polymerase chain reaction and Western blot on day 3 after TBI.Results Compared with the sham group,on days 1,3,and 7 after injuary,the TBI group,the TBI + ω-3 group,and the TBI + 3-MA group had significantly higher mNSS scores (TBI group:12.42±0.27vs.1.34±0.32,12.07±0.27vs.1.16±0.29,10.22±0.39vs.1.22±0.30;TBI+ω-3 group:12.05 ±0.23 vs.1.34 ±0.32,11.38 ±0.21 vs.1.16±0.29,8.20 ±0.21 vs.1.22±0.30;TBI +3-MA group:11.93 ±0.20 vs.1.34 ±0.32,11.09 ±0.19 vs.1.16 ±0.29,7.93 ±0.17 vs.1.22 ± 0.30;all P =0.00) and brain water content [TBI group:(79.82 ± 0.61) ％ vs.(71.87 ± 0.43) ％,(83.04±0.42)％ vs.(72.13 ±0.53)％,(75.12 ±0.72)％ vs.(71.78 ±0.38)％;TBI+ω-3 group:(76.81 ±0.63)％ vs.(71.87 ±0.43)％,(79.39 ±0.59)％ vs.(72.13 ±0.53)％,(73.86 ±0.38)％ vs.(71.78 ±0.38)％;TBI+3-MAgroup:(75.98 ±0.49)％ vs.(71.87 ±0.43)％,(77.14 ±0.46)％ vs.(72.13 ±0.53)％,(72.24 ±0.37)％ vs.(71.78 ±0.38)％;all P =0.00].The mRNA and protein expressions of LC3-Ⅱ and Beclin-1 in the brain were also significantly higher on day 3 in the TBI group,the TBI + ω-3 group,and the TBI + 3-MA group (all P =0.00).Compared with the TB1 group,on day 3 and day 7 after injury,the TBI + ω-3 group and the TBI + 3-MA group had significantly lower mNSS scores (TBI + ω-3 group:11.38±0.21 vs.12.07±0.27,P=0.04,8.20±0.21 vs.10.22±0.39,P=0.01;TBI+3-MA group:11.09±0.19vs.12.07 ± 0.27,P=0.01,7.93 ± 0.17 vs.10.22±0.39,P=0.00).Ondays1,3,and 7,compared with the TBI group,the TBI + ω-3 group and the TBI + 3-MA group had significantly lower brain water content [TBI + ω-3 group:(76.81 ± 0.63) ％ vs.(79.82 ± 0.61) ％,P =0.04,(79.39 ±0.59)％ vs.(83.04±0.42)％,P=0.01,(73.86±0.38)％ vs.(75.12±0.72)％,P=0.03;TBI+3-MAgroup:(75.98 ±0.49)％ vs.(79.82 ±0.61)％,P=0.01,(77.14 ±0.46)％ vs.(83.04 ±0.42)％,P =0.00,(72.24 ± 0.37) ％ vs.(75.12 ± 0.72) ％,P =0.02].On day 3,the TBI + ω-3 group and the TBI + 3-MA group had significantly reduced LC3-Ⅱ and Beclin-1 mRNA expression compared with the TBI group (TBI +ω-3 group:P=0.04,P =0.01;TBI +3-MA group:P =0.01,P =0.00) and protein expression (TBI+ω-3 group:P=0.01,P=0.03;TBI +3-MA group:both P=0.00).Conclusion ω-3 PUFA supplementation could markedly reduce brain edema and improve neurological functions after TBI,showing a neuroprotective effect,possibly through inhibiting TBI-induced autophagy responses.