P>Objective To investigate the effect of neuregulin 1β (NRG1β) on the neuronal apoptosis and the expressions of Bcl-2 and Bax in experimental dementia model rats. Methods Thirty adult healthy male Wistar rats were randomly divided into control group, model group and treated group consisting of 10 rats respectively. The experimental dementia models were established by injecting beta-amyloid protein 140 (AβSUB>1-40/SUB>) stereotactically into the left lateral ventricle, and treated by injecting NRG1β into right lateral ventricle. The cognitive capacity of rats was evaluated with Y-electric maze. The neuronal apoptosis was counted by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling(TUNEL) assay. The expressions of Bcl-2 and Bax were determined with immunohistochemistry assay. Results The cognitive ability in model group rats decreased, along with the number of neuronal apoptosis and the expressions of Bcl-2 and Bax increased significantly than those in control group (EM>P/EM><0.05). After treatment with NRG1β, the cognitive ability of rats improved, the number of neuronal apoptosis reduced and the expression of Bcl-2 increased while Bax decreased significantly than those in model group (EM>P/EM><0.05). Conclusion NRG1β could inhibit neurona