Visualization Of Cerebral Processing Network To Nociceptive Stimulation In General Anaesthesia State: A FMRI Study

Firstly,our researsh was to establish a stable methods for anaesthesia in rats during fMRI to compare the effects of diffirent anaesthetics;Secondly,rats fMRI scanning sequence and the methods of whole brain normalization were to be constructed;Finally,our research was to characterize the cerebral network of nociception stimulas proccessing with fMRI during diffirent anaesthetic intervals and to provide a new methods to monitor somatosensory pathway and establish prior research groundwork.Chapter 1 The comparison of the ananesthesia effects and the changes of hemodynamics and blood gas level in treatment with diffirent anesthetic agents in ratsObjectiveTo compare the ananesthesia effects and the changes of hemodynamics and blood gas level in treatment with diffirent anesthetic agents in rats for MRI scanning in this study.Methods48 SD rats were randomized into 4 groups(n=12),the rats of group A,B,C and D were intraperitoneally injected propofol(80mg/kg), ketamine(75mg/kg),2%sodium pentobarbital(40mg/kg) and 10%Chloral Hydrate(300mg/kg) respectively.A TENS supplied 3.8 mA,300μs,3Hz to the rat tail in the enviorment to simulate MRI scanning house.The body temprature,R,HR,MAP,pH,PaO2 and PaCO2 were monitored 10 min before anaesthesia,15 min after stimulation,30 min after stimulation and 5 rain after recovery.Results1.All rats rectal temprature were maintaned at 37℃-38℃.The ration of respiration of 15 min after stimulation of group A was significantly deceased when compared with those of other timepoints in same group (P＜0.05).The ration of respiration of 10 min after anaesthesia of group C and D were deceased significantly when compared with those of other timepoints in same group(P＜0.05).The HR of group A,C and D were inhibited significantly 10 min after anaesthesia when compared with those of 5 min after recovery(P＜0.05).The HR of group B were increased significantly when compared those of 5 min after recovery (P＜0.05).MAP of 10 min after anaesthesia in group A,C and D were decareased significantly when compared withe those of 15 min after stimulation,30 min after stimulation and 5 min after recobery (P＜0.05),but MAP of 10 min after anaesthesia in group B were higher than those of 5 min after recobery(P＜0.05)2.The pH of all rats had no significant changes in each timepoint(P＜0.05).PaO2 of 10 min after anaesthesia in group A,C and D were decreased significantly when compared those of 10 min after recvery.PaCO2 of 10 min after anaesthesia in group A,B and D had not been influenced at the each timepoint(P＞0.05).PaO2 of 10 min after anaesthesia in group C was lower than that of other timepoint whtin same group and PaCO2 of 10 min after anaesthesia in group C was increased at the same time(P＜0.05).3.The onset time of 10%Chloral Hydrate was shorter than that of propofol,ketamine and 2%sodium pentobarbital(P＜0.05).The onset time of 2%sodium pentobarbitalwas shorter than that of propofol,ketamine (P＜0.05).The time of recovery of group D was longer than that of group A,B and C(P＜0.05).The time of recovery of group C was longer than that of group A and B(P＜0.05).ConlusionsFour anesthetic agents are safe and effective in rats during magnetic resonance imaging.HR,MAP and blood gas datas are mantained in a normal level.Single intraperitoneal injection with 10%Chloral Hydrate(300mg/kg) is a nice method in rats during magnetic resonance imaging especialy longtime MRI scanning. Chapter 2 Functional MRI of the cerebral processing network of nociception stimulation at different anaesthesia intervalsObjectiveTo investigate the characterizations of cerebral processing network activation of nociception stimulation at different anaesthesia intervals using Functional MRI.Methods48 rats were randomized into 2 groups:the tail of nociceptive electric stimulus to rats in group T(n=24) and the left forepaw of nociceptive electric stimulus to rats in group LF n=24).All animals were anaesthetised with 10%Chloral Hydrate(300mg/kg) by single intraperitoneal injection.Using block design model,110 whole brain scanning imaging were acquired[Coil selection:SENSE-Torso;FOV: RL(mm) 50,AP(mm) 41,FH(mm) 20;TR:2000ms,TE:28ms, slice thickness:1mm;ACQ voxel matrix MPS(mm):0.63/0.49/2.0; REC voxel matrix MPS(mm):0.21/0.21/1.0;flip angle):90°]."rest" and "stimulation" were alternately carried out(off-on-off-on-off).Every tests included 30 rest whole brain scanning,10 stimulation whole brain scanning,30 rest whole brain scanning,10 stimulation whole brain scanning and 30 rest whole brain scanning.The same test was repeated 3 times 5 min later.Post-processed images were analysed with SPM2 using a multi-subject fixed effects general linear model to characterise brain specific activations and visualise cerebral processing network activation of nociception stimulation at different anaesthesia intervals.Results1 The changes of HR,MAP and blood gas analysis in 2 groups There were no significantly differences in HR,MAP,pH,PaO2,PaCO2 between 2 groups before fMRI sanning after anaesthesia (P＞0.05).HR and MAP of both groups were higher than those of 2 groups before the test(P＜0.05).There were no differences in pH,PaO2,PaCO2 which were all in normal ranges between those of before the test and after the test(P＜0.05).The datas show the physiological index of all rats are stable and brain blood perfusion are in same level.2 The changes of brain activations of rats induced by nociceptive stimulation in different anaesthesia interval2.1 SPMs for nociceptive stimulation of tail and left fore pawThe threshold of SPM was 0.005.Constant current electrical stimulation of the tail and forepaw produced rbust and localised BOLD contrast changes.These activation areas includes:primary somatosensory cortex(SⅠ),sencondly somatosensory cortex(SⅡ),Motor cortex(MC), midbrain,caudate putamen(striatum)(Cpu),visual cortex(VC),anterior cingutate(Cg),retrosplenial granular cortex(RSG),thamulus(Th), Hippoc-amps(HIP),amygdaloid nucleus(AN),accumbens nucleus(Acb), Pons(Po),medulla oblogata(MO),inferior colliculus(IC),Cerebellum.2.2 The comparision of incidence and numbers of brain activation in different anaesthesia intervalThe incidences of brain areas in 2 groups were not completely homologous.General linear mixed model determined that incidences of Cg,Cpu,Hip,SⅡ,Th of both groups during A stage were higher than those of D stage(P＜0.05) and incidences of AN,Cerebellum of T group during A stage were higher than those of D stage(P＜0.05) and incidences of Th of LF group during A stage were higher than those of C stage (P＜0.05).The sum amounts of activation during C stage were deceased significantly after 2 stage-constant current electrical stimulationin in both group(P＜0.05).The sum amounts of activation during D stage were deceased significantly after 3 stage-constant current electrical stimulationin in both group(P＜0.05).The amounts of activation during D stage in LF group and D goup were deceased significantly after 3 stage-constant current electrical stimulationin(P＜0.05).The amounts of activation during C stage in LF group were decreased significantly after 2 stage-constant current electrical stimulationin(P＜0.05).The amounts of activation during B stage in LF group were lower than that of A stage (P＜0.05).2.3 SPM group analysis for brain activations of rats induced by nociception stimulation in different anaesthesia intervalRandom-effects analysises were conducted in SPM to accounts for inter-group variation.One Sample t-tests were conducted to evaluate all your subjects for having a zero effect.The brain activation of T group invluded SⅠand SⅡ(right),RSG,AN and VPL(only A stage activation).The brain activation of LF group invluded AcbSH, SⅠ(right),VPL and RSG.2.4 SPMs for A stage minus D stage(differential) changesOne way Anova was conducted to test the fifference between A stage and B stage in 2 groups.The activation of T_A minus T_D included VP, SⅡ(left) and CA1;The activation of LF_A minus LF_D included included BLA,PAG,CMe and APtN.ConclusionsThe incidences of brain areas in 2 groups were not completely homologous in the different anaesthesia stage.The brain activation of T group invluded SⅠand SⅡ(right),RSG,AN and VPL(only A stage activation).The brain activation of LF group invluded AcbSH, SⅠ(right),VPL and RSG.In the early stage of nociceptive stimulation,The activations of T_A minus T_D include VP,SⅡ(left) and CA1 and the activation sof LF_A minus LF_D include included BLA,PAG;CMe and APtN,which is corelation with the pain descending inhibitory effects.fMRI is a good tool to monitor the central network invoving pain perception and processing,which shows perfect perspective to visualize the central effects of anaesthetics and analgesitcs.