Research On The Mechanisms Of The Cerebral Dopaminergic And Cerebral Cholinergic Neurons Post-MCC In Rats

Objective:To establish the model of multiple cerebral concussion(MCC)in rats,observe the changes of dopaminergic neurons and cholinergic neurons and its nerve fiber post-MCC,so as to understand the relation of the dopaminergic neurons and cholinergic neurons,so as to understand the neurobiologic mechanisms of cognitive behavioral dysfunction after MCC in rats.Methods:A rat MCC model was duplicated by using a metallic pendulum -striker concussive device.thirty-six male Sprague—Dawley rats were randomly divided into six MCC groups:1d,2d,4d,8d,16d and 24d group(n=6,in each group).One control was used(n=6).The substantia nigra pars compact(SNC)in midbrain,the basal forebrain,brainstem reticular formation,Manert nucleus,anterior cingulate cortex,caudate putamen,accumbens nucleus, brainstem reticular formation,Meynert cortex,post cingulate cortex,frontoparietal cortex were stained with anti-tyrosine hydroxylase(Anti-TH)and Anti-CHAT monoclonal antibody the relation of the dopaminergic neurons and cholinergic neurons by the ambi-immunohistochemistry S-P method,the number of TH or CHAT-positive neurons in the substantia nigra pars compact(SNC)in midbrain,the basal forebrain,brainstem reticular formation,Manert nucleus,anterior cingulate cortex,caudate putamen,accumbens nucleus, post cingulate cortex,frontoparietal cortex were observed and counted using optical microscope and the expression of dopaminergic nerve fiber in the different brain area was also detected. Dopaminergic neurons,cholinergic neurons and its fiber in the brain area mentioned above were quantitated by image analysis system.Results:(1)The changes of TH-positive neurons in the SNC and after MCC as followed: Compared with the control group,TH-positive neurons in the SNC increased in the 1d group following MCC,reached a peak in the 8d group,after that decreased gradually,there were significant differences in the2d,4d,8d,16d groups(p＜0.05),almost recovered in the 24d group. (2)The changes of TH-positive neurons quantitated by image analysis system in the SNC as followed:in the ld group following MCC increased in SNC,reached a peak in the 8d group,in 8d groups revealed statistical differences compared with the control group(p＜0.05),almost recovered in the 24d group.(3)The expression of the basal forebrain,the medial septal nucleus,anterior cingulate cortex,caudate putamen,accumbens nucleus,of the TH nerve fiber counted using optical microscope in the different brain regions as followed:The difference of the density of dopaminergic nerve fiber in the different brain regions was increased in the 1d group following MCC,reached a peak in the 8d group,almost recovered in the 24d group,caudate putamen neurons in the 8d group,medial septal nucleus in the 8d and 16d group,nucleus of vertical limb diagonal band in the 8d and 16d group,nucleus of horizontal limb diagonal band in the 4d and 16d group,there were significant differences(p＜0.05),almost recovered in the 24d group.(4)The changes of CHAT-positive neurons in the medial septal nucleus,brainstem reticular,dorsal nucleus of vertical limb diagonal band and nucleus of horizontal limb diagonal band after MCC as followed:positive neurons decrease in the 1d-24d group following MCC, almost recovered in the 24d group,it revealed statistical differences compared with the control group(p＜0.05)in the medial septal nucleus.dorsal nucleus of vertical limb diagonal band revealed statistical differences in the ld,2d,4d,8d group,nucleus of horizontal limb diagonal band revealed statistical differences in the ld,2d,4d group,the basal nucleus of Meynert of positive neurons decrease in the group following MCC,it reveal statistical differences compared with the control group in the ld,2d group.(p<0.05).(5)The expression ofcholinergic neurons counted using optical microscope in the basal forebrain as followed:The difference of the density of cholinergic neurons in the basal forebrain was decrease in the 1d-24d group following MCC,the medial septal nucleus in 16d revealed statistical differences compared with the control group(p＜0.05).dorsal nucleus of vertical limb diagonal band after MCC in 8d,16d and 24d revealed statistical differences compared with the control group(p<0.05).left and right dorsal nucleus of vertical limb diagonal band,the medial septal nucleus,nucleus of horizontal limb diagonal band in 8d,16d,24d revealed statistical differences compared with the control group (p＜0.05).left and right Maynert nerve only in 8d was increased following MCC,almost recovered in the 24d group,left and right Maynert nerve did not reveale statistical differences compared with the control group(p＞0.05).(6)The expression of cholinergic neurons and the TH-positive neurons fiber in the brainstem reticular formation:the cholinergic neurons decrease in the 1d group following MCC,reached a peak in the 8d group,It almost recovered in the 24d group,the level ofpontine nucleus were in the 1d,2d and 24d groups(p＜0.05)revealed statistical differences compared with the control group(p＜0.05),trapezoid body were in the 1d, 2d,8dand 16d groups(p＜0.05)revealed statistical differences compared with the control group (p＜0.05),olivary nucleus were in the 1d,2d,16d reveal statistical differences compared with the control group(p＜0.05).trapezoid body,olivary nucleus and pontine nucleus TH fiber increased in the ld group following MCC,reached a peak in the 8d group,pontine nucleus 8d, trapezoid body 16d,olivary nucleus 8d were reveal significant differences compared with the control group(p＜0.05).Conclusions:1.The multiple cerebral concussion(MCC)model in rats was established successfully using a metallic pendulum-striker concussive device;2.The expression of dopaminergic neurons and its fiber following MCC in rats increased in cerebral cortex,as well as in caudate putamen,accumbens nucleus,substantia nigra compact,the brainstem reticular formation,the basal forebrain,reached a peak in the 8d group.3.The decreasing tendency of the cholinergic neurons and their expression was observed in the basal forebrain and brainstem reticular formation following MCC in rats,especially serious on the 8^thday and 16^th day post-injury;4.The expression of TH-positive neurons following MCC in rats increased in cerebral core,however,the cholinergic neurons decrease in the alike part following MCC.Its might connection with the core and the fiber or the core and the core bewtern cholinergic neurons and dopaminergic neurons after MCC,and Its were depressioned each other.