ABSTRACT
OBJECTIVE: To study the effect of brain derived neurotrophic factor( BDNF)-tyrosine kinase receptor B( Trk B)pathway on the learning and memory impairment in rats induced by benzo[a]pyrene( B[a]P). METHODS: Seventy-two specific pathogen free healthy male SD rats were randomly divided into 3 groups with 24 rats in each group: the control group,the solvent group and the B[a]P group. The control group received no treatment. The solvent group was given intraperitoneal injection of olive oil( 1. 00 mg / kg body weight),and the B[a]P group was given intraperitoneal injection of B[a]P( 2. 50 mg / kg body weight,dissolved in olive oil) every other day. The rats were given corresponding treatment for30,60 and 90 days. The learning and memory ability of rats was evaluated using Morris water maze test. Western-blot analysis was used to detect the relative expression of BDNF and Trk B protein in hippocampus of rats. RESULTS: The escape latency of rats in the B[a]P group was longer than those in the control group and the solvent group( P < 0. 01). The duration of first passing through the platform in 3 time points in rats of B[a]P group was longer than those at the same time point in the control group and the solvent group( P < 0. 01). The target quadrant residence time and the times of passing through platform in rats of the B[a]P group were less than those in the control group and the solvent group( P < 0. 01). The duration of first passing through the platform in rats of B[a]P group increased with the increasing time of B[a]P exposure,showing a time-effect relationship( P < 0. 05). Compared with the control group and the solvent group,the relative expression of BDNF protein in hippocampus of rats in the B[a]P group was lower than those at the same time points( P < 0. 01). The relative expression of BDNF protein at time points of 60 and 90 days was lower than those at time point of 30 days in the same group( P <0. 01). The relative expression of Trk B protein in hippocampus of rats of the B[a]P group was lower than those in the control group and the solvent group( P < 0. 01). CONCLUSION: The impairment of learning and memory in rats caused by B[a]P has a time-effect relationship,which might be related to the decreased expression of BDNF and Trk B protein.