Experimental Study On Stereotactic Surgery Of Heroin-addicted Rats

Ⅰ. SummaryDrug dependence (commonly known as addiction) is a chronic progressiveobstinate disease accompanied by simultaneous strong drug-seeking behavior;knowing that drugs bring about a good many problems, a drug addict cannot helpabusing drugs. According to statistical data, the number of drug addicts all over theworld totals 230 million today, among which opiate drug abusers, predominantlyheroin (namely, diacetylmorphine) abusers, totals 15 million. The number for theregistered drug addicts in China reaches 1 million (the actual number might beseveral times over), so drug problems we are encountered with presently areextremely grim. At present, the relapse rate reaches 80%～85%, 95% and 97%respectively at one month, three months and six months after conventional treatment.Therefore, the application of surgical treatment to avoid addiction relapse is of greatnecessity, which contributes a lot to the development of human civilization.A secure surgical approach for the treatment of addiction should be establishedbasing on the exploration of its mechanism, which is still unknown to us. Reasonscausing addiction include positive reinforcement factors (euphoria and rewardingeffect), negative reinforcement factors (escapism and alleviation of abstinencesymptoms) and conditional reinforcement factors. It is believed today that negativereinforcement factors are mainly related with physical dependence caused by opiatedrugs, and the positive reinforcement effect brought about by seeking opiate drugs,namely, the rewarding effect, is the primary reason for psychological dependence ofopiate, compulsive drug-seeking behavior and relapse. Regarding the anatomicalstructures of nervous system, addiction is not invoked by the activation of specific addiction regions but by the neural loops. Two neural loops are involved in therelapse of drug addiction. One is interior wall of the hemisphere formed by a circuitof ring-type brain architecture from cingulate gyrus to hippocamp, named as limbicsystem, including septal area, fornix, anterior thalamic area and frontal lobe etc,among which the fiber connection of cingulate gyrus is the most extensive and also animportant link of limbic system. The lacertus and cingulate fasciculus passing throughthe cingulate cortex start from olfactory pyramid below the frontal lobe and theparolfactory region below rostrum corporis callosi, encircle the upper area of corpuscallosum and connect rearward with hippocampus and uncinal cortex, which are themain lacertuses connecting the limbic lobes. Anterior cingulate cortex (ACC) is thecentral structure that arouses pleasant sensation and control mood and ache. The otheris the loop of dopamine rewarding system, originates from the interior forebrainbundle in up path of dopaminergic nerve fiber of mesencephalic ventral tegmentalarea (VTA), projects onto mesolimbic dopamine system formed by nucleusaccumbens (NAC), striatum corpora, amygdale, olfactory structure and septal area etc;it almost participates all drug-dependent rewarding effects and is also theneuroanatomical foundation of rewarding effect. NAC is the last pathway ofdrug-initiated rewarding effect. Drug increases the dopamine level of nucleusaccumbens, which correlates with euphoria and reinforcement effect of addictiondrugs. The two loops are the anatomical basis for the treatment of relapse of drugaddiction. Only if the excitation-initiating effect of the loop has been blocked, drugaddiction can be cured. Meanwhile, the security and complications should be takeninto account stringently. Up until now, no reports have been released in China andoverseas about therapeutic effects of ACC and NAC on heroin, complications afterimpairment and the comparisons between intracerebral dopamine after treatment,which provides an objective for this research paper.Ⅱ. Objective of this researchThe heroin-addicted rat model was made to study the praxiology and DAchanges in limbic system pre- and post- drug addiction by rats and after damage toNAC and ACC. To further investigate the effects of NAC and ACC on drug addictionrespectively, therapeutic efficacies and complications after injury, providing references for surgical treatment in clinics.Ⅲ. Primary methods and results of this experiment:1. Methods1) GroupingA total of 50 SD male adult rats, randomly divided into group A (saline controlgroup, 10 rats), group B (10 rats with injury to nucleus accumbens after addiction),group C (10 rats with injury to cingulate gyrus after addiction), group D (10 rats withnothoinjury after addiction), and group E (addiction group, 10 rats).2). Production of heroin-dependent SD rat models:Respective 10 rats in group B, group C, group D and group E are injected withheroin solution hypodermically in a progressively increasing dosage and the 10 rats ingroup A undergo hypodermic injection with equivalent saline.3). Conditioned place preference (CPP) test procedure:Respective 10 rats in group A, group B, group C and group D. If the time of stayin pillbox is prolonged remarkably in group B, group C and group D, CPP effect musthave occurred to drugs.4). Assessment of somatic withdrawal reaction:10 rats in group A, 10 rats in group B, 9 rats in group C (late death occurred toone of the rats undergoing heroin injection), 9 rats in group D (late death occurred toone of the rats undergoing heroin injection). The second day after the lastadministration, assessment criteria of withdrawal symptoms by Maldonad et al wasapplied to assess the withdrawal symptoms of rats within 20 min and to evaluatewhether the heroin-addicted rat models had been successfully established. If theassessment for group A, group B, group C and group D (P＜0.05), it suggests that thedrug addiction models have been successfully established.5). The production of nuclear cluster-impaired animal models:10 rats in group B, 9 rats in group C and 9 rats in group D. The bilateralimpaired targets were designated by rat brain map orientation coordinate,micro-injector to the targets, rats in group B and group C were injected with 3μLglycerine (10% phenol in it) and group D underwent puncture without injection. 6). MRI examination7). CPP reassessment:CPP reassessment was performed after the 9 rats in group B, 8 rats in group Cand 9 rats in group D recovered.8). Reassessment of somatic withdrawal reaction:Withdrawal reaction reassessment by assessment criteria of Maldonad et al afterthe 9 rats in group B, 8 rats in group C and 9 rats in group D recovered.9). Y-maze test:10 rats in group A, 9 rats in group B, 8 rats in group C, 9 rats in group D and 10rats in group E. Due to the homogeneous test environment and condition applied byeach group for the evaluation of animal memory and their ability to avoid danger, thetest could be carried out only once. The correct numbers of Y-maze recorded for eachrat was regarded as the objective index for the assessment of learning speed of rats.10). DA content determination:The 10 rats in group A, 9 rats in group B, 8 rats in group C, 9 rats in group D and10 rats in group E underwent cerebral dopamine determination after decollation.11). Full-course praxiological video.12). Medical statistics; writing of science paper.13). Data statistics:Data are indicated by Mean±SD and analyzed with SPSS13.0 software package;variance analysis of single factor multiple-sample mean comparison and SNK testbetween the average number of multiple samples were executed. P＜0.05 indicatesthat there were significant statistical differences; SPSS10.0 or Origin 6.0 plot analysiswere executed.2. Results: Group A: saline control group; group B: post-addiction nucleusaccumbens -damage group; group C: post-addiction cingulate gyrus-damage group;group D: post-addiction fake damage group; group E: addiction group. Among thegroups, the assessment of withdrawal symptoms and CPP test increased evidently ingroup A and pre-ablation group B, group C and group D; the result of statisticalanalysis (P＜0.001) had statistical significance; this indicated that psychological and physical dependence of rats in group B, group C and group D had formed before theoperation. In group B, comparisons between preoperative and postoperativewithdrawal symptom assessment and the average time of stay in white box indicatedP＜0.001, and compared with group A, P＞0.05, indicating that the impaired bilateralnucleus accumbens remove the drug-seeking behavior and withdrawal symptomsessentially. In group C, comparisons between preoperative and postoperativewithdrawal symptom assessment and the average time of stay in white box showedP＜0.001, indicating that the impaired bilateral cingulate gyrus reduced thedrug-seeking behavior and withdrawal symptoms evidently, but compared with groupA, P＜0.05, indicating that the surgery had not eradicated drug-seeking behavior orwithdrawal symptoms. Comparisons between Y-maze average scores in group B,group C, group D and group E and Y-maze average scores in group A were made,indicating that P＜0.05 by statistical analysis, which had statistical significance. Theabove suggested that heroin affected the danger-avoiding and the ability in learningand memorizing of rats. The comparison between group B and group C indicated thatP＞0.05, and comparisons between group C and group D & group E both indicatedthat P＜0.05. In addition, the comparison between group D and group E indicated thatP＞0.05. The above indicated that the danger-avoiding and learning and memorizingability of rats further aggravated when the bilateral nucleus accumbens and thebilateral anterior cingulate gyrus were damaged, but there was no significantdifference between damage to nucleus accumbens or cingulate gyrus. Comparisonsbetween dopamine of group E and group A in high-effective liquid phasemeasurement limbic system indicated that P＜0.001. Comparisons between group B,group C and group D after mutilation indicated that P＞0.05; the content of dopaminedecreased but having no significant difference.Ⅳ. Summary of the science paperBased on the researches in heroin-addicted models and impairing approaches,combined with the actual situation in the laboratory and after repeated pre-trials, weare able to establish comparatively fulfilled heroin-addicted rat models and precise,secure and simple impairing approaches. Our tests indicate that NAC takes thepredominant position in regulating the consolidating effects of drugs on rats and is also the primary structural basis for psychological dependence of drugs. Anteriorcingulate gyrus is one of the focal components of central rewarding system. Theincrease in DA level of limbic system is a necessary condition for the occurrence ofrewarding effect, and the rewarding effect is a key factor in determining if thepsychological dependence may develop. The development of psychologicaldependence depends on the increase in DA level of NAC; however, whenpsychological dependence has developed, it may exist with the absence of DA. Thismight explain the reason why the trend of change in DA level of limbic system afterthe rats' nucleus accumbens has been damaged is inharmonious with the rhythm ofchange in CPP; meanwhile, it also shows that the occurrence of psychologicaldependence correlates with much more complex mechanism beside DA, e.g. thestimulant amino acid (like glutamic acid) participates the addiction process throughaffecting the ability of learning and memorizing.In conclusion, this research testifies that the heroin addiction can be effectivelytreated with through the impairment of nucleus accumbens or cingulate gyms, and theimpairment of nucleus accumbens brings better effect than that of cingulate gyrus.Recent observation indicated that rats had taken less food and felt exhausted ere, butthese symptoms vanished 1 week later, which might be related with cerebral edemaafter impairment. Short-term postoperative observation found that mutilation hadsome effect on the rats' ability of learning and memorizing, which gave somereference for the surgical treatment of addiction. After nucleus accumbens of rats hadbeen damaged, the trend of change in DA level of limbic system was inharmoniouswith that of CPP, indicating that the mechanism for neurotransmitter andpsychological dependence are still not clear and further testifying that besidesdopamine, 5-HT, glutamic acid and acetylcholine participates the occurrence ofpsychological dependence, but still awaiting further study.