| Adrenergic receptors,which belong to G protein coupled receptors,can be combined with epinephrine and norepinephrine,and are spread all over the central and peripheral nervous system.Pharmaceuticals targeting adrenergic receptor are widely used,and have become one of the important pollutants of aquatic environment in the form of the prototype compounds or metabolites.As one species of the model fish,medaka were commonly used at present,while most of the studies focusing on the embryonic development,swimming and social behavior of adult fish,as endpoints of chemical toxicity.In this study,using the newly hatched medaka larvae as the experimental animal,we established a set of swimming behavior assay under light and dark for toxicity assessment.Based on this assay,the β-agonist ractopamine(RAC)and β-blocker propranolol(PRO)were selected as typical adrenergic receptor related drugs,and the effects of two drugs on medaka larvae behavior,as well as the mechanism of neurobehavioral toxicity.The results showed that low concentration RAC exposure resulted in the increase of swimming speed(about7-38mm/min)of larvae in dark,while in light,exposure to high concentration decrease the swimming speed(4-15mm/min).No gender specific effect of RAC on the swimming speed was found as well.For PRO,the swimming speeds of medaka were significantly increased at low concentration while decreased at higher concentration in the darkness,whereas no change was found in the light.A significant difference was observed between the behavior of male and female larvae exposed to low concentration of PRO.Additionally,the transcription of those genes related to the nervous system development were studied,and both RAC and PRO exposure could produce the changes of their mRNA levels.These results suggested the exposure of adrenergic receptor related drugs caused neurobehavioral toxic on fish,which was helpful for the comprehensive risk assessment for these chemicals. |
