Effects of Naokang Erhao decoction on cognitive ability and hippocampal apoptosis-related proteins in diabetic rats

Abstract

To investigate the effects of Naokang Erhao decoction on the cognitive ability and the expression of Caspase-3, Bax and Bcl-2 proteins in hippocampus of type 2 diabetic rats. The diabetes mellitus (DM) rat model was produced by intraperitoneal injection of streptozotocin and fed with high fat and sucrose diet. The Naokang Erhao-treated rats were intragastrically given different doses of Naokang Erhao, whereas the control and DM model groups were given double distilled water for 4 consecutive weeks. Learning and memory abilities of rats were tested with the Morris water maze. The expression of Caspase-3, Bax and Bcl-2 proteins in hippocampal CA1 region was measured by immunohistochemistry. Both escape latency and swimming distance of type 2 DM rats were significantly prolonged in comparison of those in normal control (P < 0.01), and swimming time in the platform of previous quadrant was significantly shorter in model group (P < 0.01). Furthermore, the expression of Bcl-2 protein was decreased, while Caspase-3 and Bax in the hippocampus were increased compared with the control group (P < 0.01). Four weeks of treatment with Naokang Erhao decoction remarkably improved the learning and memory abilities of DM rats, increased the expression of Bcl-2 and decreased the expression of Caspase-3 and Bax in hippocampal CA1 region of model rats (P < 0.01 or P < 0.05). Naokang Erhao decoction may inhibit apoptosis by increasing the expression of Bcl-2 and reducing the expression of Caspase-3 and Bax in the hippocampus, and this may be one of the mechanisms by which Naokang Erhao decoction improves cognitive ability in DM rats.