Objective To investigate the alteration of chaperone hsp40 and its effects on the dealyed neuron death in the CAI neurons after transient cerebral ischemia.Method Twenty-minute transient global ischemia rat model was used.Following different repeffusion period,all the 28 wistar rats were divided into sham-operation group ,4-hour recovery group,24-honr recovery group and 72-hour recovery gronp,7 ratsin in each group,Immunochemistry and laser scanning confocal microscopy were used to observe the distributional alteration of hsp40 in the neurons.Differential centrifuge and westemblot analysis were used to analyze the quantitative alteration of hsp40 and its redistribution in the neurons.Results lnanunechemistry and laser scanning confocal microscopy showedthe reduction of hsp40 first in cytosol,then in the nucleus until all the neurons in the CAI region died.Differential centrifuge and westemblot analysis showed the quantity of hsp40 decreased from (1.00_+0.21) to (0.23±0.13)(P<0.01) after 24-hour repeffusion;the quantity of hsp40 in the protein aggregates increased from (1.00±0.18) to(8.61±1.89)(P<0.01) after24-hour reperfusion.Conclusions The reduction of hsp40 in the neurons of hippocampus CA1 region is an important factor resulting in protein aggregates formation.