Abstract: Objective To detect differential expressions of brain type isoenzyme of creatine kinase(CK-BB)in the brain of hens with organophophors compounds induced delayed nerutoxicity(OPIDN)and to provide target protein evidence for diagnosis of POIDN.Methods Twenty-four Roman hens were randomly divided into three groups:treated group(1 000 mg/kg triorthocresyl phosphate,TOCP),intervened group(40 mg/kg phenylmethanesul fonyl fluoride PMSF before TOCP treatment),and control group(tap water).Eight hens in each group were sacrificed at day 5 and day 20 after the treatments;then,the brain tissue of the hens were seperated at low temperature and total protein of the brain tissue were extracted.With solid phase PH gradient sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE)and two-dimensional electrophoresis and mass spectrometry,we detected differently expressed CK-BB protein.Results Compared with the control group,the difference in CK-BB expression was not significant at day 5(P<0.05),while at day 20,the gray level ratio of CK-BB expression of treated-group and intervened-group were 0.327 5 and 0.675 7,with a three-fold down-regulation in the treated group.Mass spectrometry and Swiss-por data analysis identified CK-BB spot with peptide segments of 26,sequence coverage of 75%,and the assessment value of 1 603(≥45 for high reliability)in relation to the species of the hen and protein sequence number gi|45384340 of CK-BB.Conclusion The expression of CK-BB is down-regulated in the brain of hens with OPIDN,which may related to brain injury induced by OPIDN.