Aim To investigate dynamic changes of water content and neuropetie Y(NPY) in intracerebral hemorrhagic(ICH) rats and the role that neuropetie Y plays in cerebral edema after hemorrage,and to evaluate the effect of aprotinin in reducing the content of cerebral edema and neuropetie Y.Methods Animal model was made by injecting self arterial blood into the caudate nucleus of rats.75 rats were randomly assigned to control group,cerebral hemorrhage group and aprotinin treated group.After the injection,the rats were sacrificed at 6 h,1 d,3 d,5 d,7 d respectively.Brain water content was determined by wet-dry weight,as the expression of neuropetie Y was detected by radioimmunoassay method over a time course ranging from 6 hours to 7 days.Results Brain water content and neuropetie Y increased after 6 hours of cerebral hemorrhage and reached its climax at the 3 days,then decreased at the 5 to the 7 days;Administration of aprotinin could reduce the content of brain edema and neuropetie Y.Conclusions Aprotinin can reduce neuropetie Y expression,thus can reduce cerebral edema after ICH.Aprotinin antagonist might be available for the therapy of cerebral edema after ICH.