The Relationship Between Neurotoxicity Induced By Benzo[a]Pyren And Distribuiton Of Benzo[a]Pyren In Brain Tissuse

PartⅠTHE MORPHOLOGICAL CHANGES IN RAT'S HIPPOCAMPUS INDUCED BY BENZO[A]PYRENEObjective: To study the morphological changes in rat's hippocampus induced by benzo[a]Pyrene by light and electric microscopic.Methods: 48 SD male rats(21-day-old) weighted 40-50g were divided into control group (n=8) and test group (n=40), experimental animals were given a single intravenous injection of 3.7×105Bq/kg of 14C-B(a)P while the same doses of Normal Saline were given to the control group. The rats were sacrificed at 1hour, 1 day, 2 days, 3days and 7 days after the administration of radiolabelled B(a)P. During the experiment, some toxicological symptoms were observed. Light and electric microscopic were used to observe the morphological changes in rat's hippocampus induced by benzo[a]Pyrene.Results: (1) The changes of toxicological symptoms are observed. (2) No significant morphology changes of hippocampus between BaP treatment and control group by light microscopic. (3) Electric microscopic show that hippocampus in BaP treatment groups, endocytoplasmic reticulum expanded, mitochondria swelled, broken, the bars were reduced and disappeared,while no significant changes be seen in control group.Conclusion: The nerve cells in hippocampus are injured by BaP.PratⅡEFFECTS OF BENZO(A)PYRENE EXPOSURE ON SPACIAL LEARNING AND MEMORY ABILITIES OF SD RATObjiective: To establish the benzo(a)pyrene exposure SD rat's model and study the effects of benzo(a)pyrene exposure on spacial learning and memory abilities of rat.Methods: 40 SD male rats(21-day -old) weighted 40-50g were randomly divided into 4 groups with each of 10 rats including 3 administrated groups. 1 control group and 3 experiment groups , all rats in 3 administrated groups were intraperitoneally administrated BaP dissolved in corn oil at dose levels of 2.5mmol/L, 5mmol/L,10mmol/L respectively for 2 times per week. The mice in control group received an equal volume of corn oil. The administration lasted for 4 weeks and general state of rat's health was recorded. Their spacial abilities were tested by their performance in Morris water maze. We judge the effects of different dosage BaP on spacial abilities by testing the platform locating latency, error numbers and the times that rats stepped over the platform at 0 day, 30 days, 40 days and 50 days after administration.Results: (1) Platform locating latency made by rats in BaP exposure groups was longer than that of the control group (p<0.05). The high dose of 10mmol/l group was more notable (P<0.05). (2)There was significant difference in platform locating latency between the control group and the exposure ones at 30 days after administration, in which high dose group is longest, followed by middle dose group and control group is lowest(p<0.05). Platform locating latency is reduced along with the time extension after administration. (3) Notable difference in error number was seen between the control group and BaP exposure one (p<0.05). The dose of 10mmol/l group was more notable (P<0.05). (4) There was significant difference in error numbers between the control group and the exposure ones at 30 days after administration, in which 10mmol/l group was longest, followed by 2.5mmol/l group and control group is lowest(p<0.05). Error numbers were increased along with the time extension after administration. (5) Compared to the control group, the frequency of BaP exposure groups to step over the platform location decreased notably (p<0.05).And the difference in BaP exposure groups was notable in stepping over the platform location (p<0.05).Conclution: (1) The spacial learning and memory abilities of BaP exposure rat are injured. (2) There are dosage effect relation between the BaP exposure dosage and the injury of rat's learning and memory abilities. (3)The injury induced by BaP will recover partly after stopping administration.PartⅢLIGHT MICROSCOPIC AUTORADIOGRAPHY OBSERVATION ON THE DISTRIBUTION OF BENZO(A)PYRENE IN THE RAT BRAIN TISSUEObjective: To study the dynamic distribution of B(a)P in the rat model of brain tissue by light microscopic autoradiography.Methods: 68 SD male rats(21-day-old) weighted 40-50g were divided into control group (n=8) and test group (n=60), experimental animals were given a single intravenous injection of 3.7×105Bq/kg of 14C-B(a)P while the same doses of Normal Saline were given to the control group. The rats were sacrificed at 1, 6, 12, 24 and 48 hours after the administration of radiolabelled B(a)P. During the experiment, some toxicological symptoms were observed and the ratios of brain-weight/body-weight were detected. Light microscopic autoradiography and r-counting were used to observe the dynamic distribution of BaP in brain tissue.Results (1)No significant difference was detected in brain-weight/body-weight. (2)R-counting and light microscopic autoradiography showed that [14C]BaP centralize in hippocampus at 1h, they centralize in cerebral cortex at 6h and centralize in corpus striatum at 24h after treatment. (3) Compared with the control group, silver granules in BaP treatment group are higher . And the silver granules distribution is not homogeneously. After the administration, silver granules increase along with the time increasing, which reach the peak in 24h and sharp decrease in 48h. (4)The silver granules distribution is higher in neuron than in neurogliocyte. The difference is notable.Conclusion: B(a)P can penetrate the blood-brain barrier and distribute in every regions of rat brain, inducing brain tissue injury.