Normal saline group was injected with normal saline. L Arg/S group and L Arg/L group were injected with L Arg. L NNA group was injected with L NNA.

• 生理盐水组静脉注射生理盐水 ,L Arg/S组和L Arg/L组静脉注射不同剂量L 精氨酸 ,L NNA组静脉注射L 硝基 精氨酸。