Study on the Mechanism of AMD Regulating Orexin Signaling Pathway to Improve Learning and Memory of SD zebrafish Model
Objective To observe the effects of AnMeiDan(AMD),a representative formula of Peiyuan Guben Tranquilisation method,on the learning memory of zebrafish model of sleep deprivation(SD),and to explore the possible mechanism and the optimal apparent dose based on the Orexin signalling pathway.Methods 120 4-month-old wild-type AB line zebrafish were randomly divided into blank group,model group,AMD low-dose group(0.009 mg·mL-1·d-1),AMD medium-dose group(0.027 mg·mL-1·d-1),AMD high-dose group(0.081 mg·mL-1·d-1),and melatonin group(0.4 mg·mL-1·d-1).Zebrafish SD model was established by LED light induction method,24 h behavioural changes of zebrafish in each group were monitored by zebrafish behavioural tracking system,differences in learning and memory ability of zebrafish in each group were detected by T-maze,the state and number of neurons in the brain of zebrafish in each group were observed by Hematoxylin-Eosin(HE)staining method,the structural changes of neurons in the brain of zebrafish in each group were observed by transmission electron microscopy,and changes in neuron structure in the brain of zebrafish in each group were detected by ELISA method.The levels of Orexin A(OXA)and Orexin B(OXB)in zebrafish were detected by enzyme-linked immunosorbent assay(ELISA),and the protein and mRNA expression levels of OXA/p38 mitogen-activated protein kinase(P38 MAPK)/extracellular regulated protein kinase(ERK1/2)were detected by protein immunoblotting and real-time fluorescence quantitative assay(RT-PCR)in zebrafish.Results Compared with the blank group,the total number of rests,duration and distance were reduced in the model group(P<0.05),and the latency to enter the target region(OR)was prolonged(P<0.01);the number of neuronal cells was reduced,the nuclei were degenerated(P<0.01),cytoplasmic hyalinosis was increased(P<0.01),and light colouring was observed,the nuclei were collapsed,the nuclear membranes were ruptured and lysed,the chromatin was solidified,and the mitochondria were swollen and deformed with internal cavities,and lamellipod-like myelin-like structure was formed;the brain tissue OXA,OXA,and ERK1/2 expression levels of the mRNAs and the mRNAs of these signaling pathways were increased(P<0.01).brain tissue OXA and OXB proteins were significantly elevated,OXA mRNA and protein were significantly up-regulated,and P38 MAPK and ERK1/2 mRNA and protein were significantly down-regulated(P<0.01).Compared with the model group,the drug intervention could prolong the total resting exercise time of SD zebrafish(P<0.05);shorten the latency of zebrafish to reach OR(P<0.05);protect the structure and morphology of neuronal cells,and alleviate the damage of brain tissues;reduce the content of OXA and OXB in the brain tissues(P<0.01);and down-regulate the expression of OXA mRNA and protein(P<0.01),and up-regulate the P38 MAPK and ERK1/2 mRNA and protein expression of P38 MAPK and ERK1/2(P<0.01);and the quantity-effect relationship was obvious,and the effect of high dose of AMD was optimal.Conclusion AMD can improve the learning and memory ability in zebrafish SD model,and its mechanism may be related to the regulation of OXA/P38 MAPK/ERK1/2 signalling pathway and alleviation of neuronal damage in the brain,and the high dose group of AMD showed the best effect.
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