Study Of Enrofloxacin On Blood-brain Barrier Permeability And Brain Tissue Damage Of Pengze Crucian Carp(Carassius Auratus Var. Pengze)

In order to explore the effects of Enrofloxacin on blood-brain barrier permeability and brain damage of fish,and to explore the role of brain injury markers in the evaluation of brain tissue damage of fish,Pengze crucian carp（Carassius auratus var.Pengze）was used in this thesis as the research object by single front oral administration.The results showed that Enrofloxacin residues could be detected in all tissues of crucian carp after single oral administration Enrofloxacin of lethal dose of 50%(LD₅₀,1949.84 mg/kg)and safe dose（SD,194.984 mg/kg）ENF to crucian carp.It was observed that Enrofloxacin residue was high in the brain tissue of crucian carp,which indicated that Enrofloxacin had good permeability to BBB of crucian carp.The Enrofloxacin residue of LD₅₀and SD groups were 0.154 and 0.099μg/g at 960 h respectively,which were higher or equal to the limit of Enrofloxacin in fish muscle.The brain tissue of crucian carp was suitable for the detection of Enrofloxacin residues.Under LD50 and SD groups,two brain injury markers,S100B and NSE proteins in 24 time-points of crucian carp were extremely significant higher that of in blank control group（P<0.01）.The serum GFAP level in LD₅₀group was higher than that of in blank control group（P<0.01）,while there was no significant difference in GFAP content among the SD group（P>0.05）.Among the correlation analysis of Enrofloxacin residues and the three markers,S100B(LD₅₀:0.514*,SD:0.677**)and NSE(LD₅₀:0.446*)were significantly correlated,indicating that S100B,NSE and GFAP could all be used as evaluation indexes for brain injury of crucian carp.The serum S100B content could be regarded as the evaluation index of Enrofloxacin residue in crucian carp brain.The result of histopathology and frozen sections showed that Enrofloxacin of LD₅₀could cause different degree of pathological changes in the brain tissue of crucian carp at 96 h,showing sparse neural network and deep staining of glial cells.After Evans blue staining,the brain tissues at LD₅₀and SD groups showed dispersion distribution and increased content of Evans blue.It suggested that Blood-brain barrier permeability increased.Detection of genes and proteins related to Blood-brain barrier in crucian carp,LD₅₀and SD Enrofloxacin both induced the down-regulation of claudin-5,Occludin and P-glycoprotein（P<0.01）.Meanwhile,the expression of brain-derived protein S100B and GFAP gene were significantly up-regulated（P<0.01）,while the expressions of NSE gene were significantly down-regulated（P<0.01）.Western blot analysis showed that the expressions of Occludin and P-glycoprotein were significantly down-regulated（P<0.01）.The expressions of NSE and GFAP were significantly up-regulated（P<0.01）.These results suggest that Enrofloxacin could cause brain injury in crucian carp by inhibiting the expression of related genes and proteins on blood-brain barrier.