A Study On The Construction Of Neural Network Of Orexin Nuclei And Its 3D Visualization In Alzheimer's Disease

Objective:Orexin,also known as hypocretin,is an important central neuropeptide of the body.It's involved in many physiological processes of the body,such as regulating dieting behavior,sleep-wake cycle and learning-memory.The distribution of Orexin nuclei and the projection of nerve fibers determine their physiological functions.Orexin is densely distributed in the brains of lower vertebrates of zebrafish and mammalian animal of mouse,but there is still a lack of complete microscopic anatomical network reconstruction.Alzheimer's disease(AD)is a severe neurodegenerative disease,typically characterized by progressive memory loss and cognitive decline,which poses a significant threat to the physical health and quality of life of the elderly.Studies have shown that Orexin is involved in the early to late pathological process of AD,and has important effects on the amyloid protein metabolism and sleep-wake of AD,but the distribution characteristics and dynamic changes of Orexin neurons in AD model are still unclear.This study focuses on the Orexin microscopic anatomical network,aiming to provide histomorphological basis for the further study of Orexin system function by analyzing and comparing the 3D images of Orexin neural network between species,normal and AD pathology.Methods:The whole brain tissue of normal adult zebrafish at 6 months,normal adult at 8 months,and APP/PS1 transgenic mice at the same age were taken,and the sequence sections were made,then the digital slice scanning system was used to obtain the digital slice information.(1)The distribution trend of Orexin neurons in zebrafish,wild-type mouse and AD model mouse were compared and analyzed by immunohistochemistry and sequence sections imaging.(2)The distribution range of Orexin neurons can be visualized through three-dimensional reconstruction.(3)The complete morphological and distribution characteristics of Orexin neurons in the brain were observed by preparing the transparent brain of the animal model and combining with immunofluorescence technique.Results:(1)In the zebrafish brain,Orexin cells are mainly located below the Periventricular grey zone of optic tectum(PGZ),and densely distributed between Fasciculus retroflexus(FR),Commissura horizontalis(Chor)and Commissura posterior(Cpost).Continue to the rear were centered in the Rostral tegmental nucleus(RT),Medial preglomerular nucleus(PGm),and Posterior thalamus nucleus(PTN).In the mouse brain,Orexin cells were intensively expressed in the Perifornix nucleus(Pe F)and Lateral hypothalamic area(LH)from the level of bregma-1.94 mm.In addition,Orexin neurons were scattered symmetrically on both sides of the Third ventricle(3V),this characteristic continued until Pe F and LH disappeared,presenting a sparse-dense-sparse distribution state from front to back.Orexin neurons occupy about 450 ?m thick diencephalon in zebrafish,and about 1000 ?m thick of hypothalamic tissue in mouse.(2)As a whole,Orexin neurons in both WT and APP/PS1 mouse were located in the tubercular hypothalamus region,on both sides of the Third ventricle(3V),between the Mammillothalamic tract(mt)and the white matter bundle of Fornix(f),with a tendency of approximately Normal Distribution,and APP/PS1 mouse had a wider distribution range and a longer distribution curve along the sagittal axis than WT mouse.Partitions: Compared with WT mouse,the number and density of Orexin cells in APP/PS1 mouse were significantly increased in the anterior region,the central region and the posterior region.The number of cells in anterior region and central region were significantly higher than that in the control group.Layers: The distribution of Orexin neurons in APP/PS1 mouse was mainly between bregma-1.06 mm and-2.30 mm,and the layer thickness was about 1.24 mm,WT mouse were mainly located between bregma-1.34 mm and-2.18 mm,and the layer thickness was about 0.84 mm.Even though the same section,Orexin cells were distributed in different nuclei.For example,at the level of bregma-1.82 mm,APP/PS1 mice were expressed in the LH,Pe F,Magnocellular nucleus of the lateral hypothalamic(MCLH)and Dorsomedial nucleus(DM),while WT mouse were not expressed in the DM region.Single cell: There was no significant difference in cell morphology and diameter,which were from 10 ?m to 25 ?m.Conclusions:(1)In zebrafish,Orexin cells are mainly located in the anterior part of the diencephalon,while in mouse,they are located in the lower part of the diencephalon(hypothalamus),and the main nuclear clusters are also different,suggesting that Orexin may play different functions in different organisms models.(2)In the pathological state of AD,the number of Orexins cells increased significantly,and the distribution of nuclei changed significantly,especially in the nuclei associated with sleep-wakefulness and dieting,suggesting that Orexin have a particularly prominent influence on AD sleep and dieting disorders.