Objective To study the effects of exogenous phosphocreatine (CP) on brain injury after cardiopulmonary resuscitation (CPR) in rats.Methods A total of 160 male adult SD rats were randomly ( random number) divided into 4 groups:sham-operation control group ( group A),CPR group ( group B),low-dose CP group ( group C),high-dose CP group ( group D),and each group was further divided into 5 subgroups (n =8) as per study at different intervals,0.5,3,6,12 and 24 h after restoration of spontaneous circulation (ROSC) in groups B,C and D or after tracheotomy in group A.Cardiac arrest (CA) was induced by using asphyxia to establish CPR model in group B,C and D.The CP0.5 g/kg used in group C or CP 1.0 g/kg used in group D was injected into femoral vein at beginning of ROSC.Rats in each subgroup were sacrificed and the tissues of frontal lobe of brain of rats were taken at different intervals.The levels of adenosine triphosphate (ATP),adenosine diphosphate (ADP) and adenosine monophosphate (AMP) in cerebral cortex were measured by high performance liquid chromatography (HPLC),and values of total adenine nucleotides ( TAN ) and energy charge ( EC ) were detected.The activities of Na+ -K+ -ATPase and Ca2+ -Mg2+ -ATPase in cerebral cortex were assayed by spectrophotometric method. The pathological changes of cerebral cortex were observed under optical microscope.The experimental data were processed with analysis of variance by using SPSS 16.0 package. Results Compared with group A,the levels of ATP,TAN,EC,Na + -K + -ATPase,Ca2+ -Mg2+ -ATPase were lower ( P ＜ 0.05 or P ＜ 0.01 ) at each interval in groups B and C,and at intervals of 0.5,3,6,12 h in group D,and the levels of AMP were higher (P ＜ 0.01 ) at each interval in group B and at intervals of 0.5 h and 3 h in groups C and D.Compared with group B,the levels of ATP,TAN,EC,Na + -K + -ATPase,Ca2 + -Mg2+ -ATPase were higher ( P ＜ 0.05 or P ＜ 0.01 ),and the levels of AMP were lower ( P ＜ 0.05 or P ＜ 0.01 ) at intervals of 6,12 and 24 h in groups C and D.Compared with group C,the levels of ATP at interval of 24 h and TAN,Na +- K + -ATPase,Ca2 + -Mg2 + -ATPase at intervals of 6,12 and 24 h were higher in group D ( P ＜ 0.05 or P ＜ 0.01 ).There were severe pathological changes in cerebral cortex in group B,and mild changes in groups C and D. Conclusions There was obvious energy metabolism disorder after CPR in rats.Treatment with exogenous CP could increase the levels of ATP and activities of ATPase,alleviate pathological changes,especially in high-dose,and mitigate injury in cerebral cortex after CPR in rats.