Abstract: Objective To probe the influence of deep hypothermic circulatory arrest on expression of MMP-9 and NPY in brains of rat. Methods Rats were divided randomly into three groups: normal comparison group (NC), normal temperature circulatory arrest group (NTCA) and deep hypothermic circulatory arrest group (DHCA). After establishment of the extracorporeal circulation model, the NC group with no hypothermia or circulatory arrest, maintain circulatory 10 min under in normal temperature. In NTCA group, rats were circulatory arrested under normal temperature with 10min. In DHCA group, circulatory arrest were performed in 18.5℃～20℃ with 10min. Then removed the brains immediately, used dry-wet way to measure water content of the brains, and used immunohistochemical way and Western Blot to measure the expression of MMP-9 and NPY. Results The water content of the brains in NTCA group is much higer than that in DHCA group and NC group, but the survival rate of nerve cells in NTCA group is lower than that in other two groups obviously (P<0.05). The expression of MMP-9 in NTCA group and DHCA group was much higher than that in NC group (P<0.05), and the expression of MMP-9 in DHCA group was lower than that in NTCA group (P<0.05). The expression of NPY in NTCA group and DHCA group was much lower than that in NC group (P<0.05), but in DHCA group, the expression of NPY is higher than that in NTCA group (P<0.05). Conclusions Deep hypothermia can increase the survival rate of neurons by reducing the magnitude of NPY and the expression of MMP-9.

Key words: [KEY WORDS] MMP-9, NPY, external circulation arrest, deep hypothermic