BLOOD-BRAIN BARRIER PERMEABILITY OF DIF AND ITS ELIMINATION COMPARATIVE STUDY BETWEEN BRAIN AND PERIPHERAL TISSUES IN CARASSIUS AURATUS GIBELIO

Nowadays, difloxacin (DIF) which belongs to Fluorine quinolones (FQNS), has become one of the widely used drugs. For aquatic animals, the permeability of DIF getting through blood-brain barrier has not been reported. Using Carassius auratus gibelio as the research object, the blood-brain barrier permeability of DIF and its elimination comparative study between brain and peripheral tissues were conducted with tissue homogenate and high performance liquid chromatography (HPLC) methods. The results showed that, at the 96th hour, the content of DIF in brain tissue homogenate was (10.490.35) g/g following its 96 hour median lethal dose (96h LD50); and the existences of DIF in brain could be detected at the 15 time points (0960h) after the administration with its clinical recommended dosage (20 mg/kg). The results indicated that the DIF could penetrate through the blood-brain barrier into brain of C. auratus gibelio. In addition, the elimination process of DIF in brain after the administration of 20 mg/kg was the gentlest one among the tissues involved in this research. The highest content of DIF in brain was (0.3920.007) g/g. The highest value was reached at the 960th hour. The longest T1/2 of DIF in brain was 1157.713h. The brain of C. auratus gibelio could be used as a target tissue for DIF residual analysis. Furthermore, according to the regulation of European Union (2003) about the maximum residue limits (MRL) of DIF on food, the withdrawal time of DIF should be longer than 25d under the experiment conditions. The results would provide references for blood-brain barrier researching in fish, and for nerve toxicity explorations of DIF and its clinical application in aquaculture.