Changes in neurosteroid levels and steroidogenic enzyme expression in the brain of morphine dependent and withdrawing rats

BACKGROUND： Studies have demonstrated that exogenous neurosteroid treatment prevents the development of morphine tolerance and dependence, and attenuates abstinence behavior in mice. However, there are few studies on whether the levels of endogenous neurosteroids can be changed by morphine dependence and withdrawal. OBJECTIVE： To investigate the levels of various neurosteroids in rat brain following morphine dependence and withdrawal. To evaluate the expressions of steroidogenic enzyme mRNAs and proteins. To identify the relationship between neurosteroids and morphine dependence at the whole animal behavior, neural biochemistry, and molecular levels. DESIGN, TIME AND SETTING： A randomized, controlled study. Experiments were performed at the Department of Pharmacology of Hebei Medical University and Department of Pharmacology of Beathune International Peace Hospital, China, from June 2004 to October 2007. MATERIALS： Morphine hydrochloride injection （Shenyang First Pharmaceutical Factory, China）, naloxone hydrochloride （Hunan Yiqiao Pharmaceutical Co., China） and a gas chromatography-mass spectrometry system （Agilent, CA, USA） were used in this study. METHODS： Healthy adult Sprague Dawley rats were randomly divided into three groups： a morphine dependence group, morphine withdrawal group and control group （n = 20）. The rats in the morphine dependence and morphine withdrawal groups were given increasing doses of morphine （5, 10, 15, 20, 30, 40 and 50 mg/kg, intraperitoneal） to create morphine dependence. The rats in the morphine withdrawal group were injected with 2 mg/kg naloxone to precipitate withdrawal 1 hour after the last morphine injection. Rats in the control group were treated with an equal volume of saline. MAIN OUTCOME MEASURES： Following morphine dependence and withdrawal, brain levels of the neurosteroids pregnenolone, progesterone and allopregnanolone were analyzed using gas chromatography-mass spectrometry. The mRNA expression of two key steroidogenic enzymes, P450 side-chain cleavage enzyme （P450scc） and 3[B-hydroxysteroid dehydrogenase （313-HSD）, were determined in rat brain regions using reverse transcription-polymerase chain reaction. The distribution and expression of P450scc protein were visualized in brain regions associated with addiction by immunohistochemistry. RESULTS： In brain tissue from the morphine dependence group, the levels of pregnenolone and progesterone were decreased by 62% （P 〈 0.01） and 92% （P 〈 0.01 ） respectively, compared with the control group. In the morphine dependence group, the key steroidogenic enzyme P450scc mRNA was decreased in striatum （P 〈 0.05）, while 3-HSD mRNA was decreased in amygdala （P 〈 0.05）, striatum （P 〈 0.05） and frontal cortex （P 〈 0.05） compared with the control group. Morphine withdrawal induced a significant increase in the neurosteroid levels compared with the control group （P 〈 0.01）. However, there was no significant difference in the expressions of P450scc and 36-HSD mRNAs between the morphine withdrawal and control groups （P 〉 0.05）. CONCLUSION： The neurosteroid levels and expressions of steroidogenic enzymes changed similarly in morphine dependent rats, suggesting that the morphine dependence-induced decrease in neurosteroids might depend on local expression of steroidogenic enzymes in the central nervous system. However, the changes in neurosteroids in morphine withdrawal rats were not in accordance with the changes in the expression of steroidogenic enzymes, suggesting that the effects of morphine withdrawal on brain neurosteroid levels may not depend primarily on the local expression of steroidogenic enzymes in the central nervous system.

Postmortem regional distribution of morphine in dependent rats

Objective: Morphine concentration measured in postmortem tissues may or may not reflect antemortem concentration. We measured levels of morphine in autopsied tissues to determine whether morphine distribution in morphine-dependent rats is altered after death. Methods: Solid-phase extraction was used to extract morphine from the samples, and morphine levels were measured at 0-96 h postmortem using gas chromatography. Results: The study of the morphine dependent rats showed a significant (P<0.05) increase of morphine concentration in postmortem cardiac blood, liver tissues and kidneys tissues. A significant increase was also observed at 72 h and 96 h postmortem in the brain, while morphine levels in cardiac tissues only increased at 24 h and 96 h postmortem. These changes were associated with an observed pH rapid decrease: pH of cardiac blood dropped from 7.36±0.15 to 6.86±0.09 (P<0.01), pH of liver tissues from 6.98±0.04 to 6.34±0.03 (P<0.05). Conclusion: The postmortem regional distribution of morphine occurs in dependent rats, but different from the change that occurs in acute poisoning rats. The morphine concentration in cardiac blood and tissues tends to increase during the period of 0-96 h postmortem in dependent rats. Morphine concentration increases with pH rapid decrease. The antemortem internal amount of morphine affects its postmortem regional distribution. It appears that several mechanisms are accountable for postmortem morphine distribution. The understanding of the mechanisms and patterns may eventually lead to better choices of samples which may better represent antemortem drug levels.

Sidiming attenuates morphine withdrawal syndrome and nitric oxide (synthase) levels in morphine-dependent rats and rhesus monkeys

The present study analyzed the effects of Sidiming, a Chinese herbal compound, on withdrawal syndrome, body weight loss, and serum levels of nitric oxide and its synthase in morphine- dependent rats and rhesus monkeys. These effects were compared with clonidine, an active control drug used for clinical treatment. Results showed that 4 and 8 g/kg Sidiming, respectively, significantly suppressed morphine withdrawal syndrome and reduced body mass loss in morphine-dependent rats. In addition, 2.4 and 4.8 g/kg Sidiming, respectively, significantly attenuated withdrawal syndrome in rhesus monkeys. High-dose Sidiming （8 g/kg in rats and 4.8 g/kg in rhesus monkeys） led to significantly inhibited serum levels of nitric oxide and its synthase in morphine-dependent rats and rhesus monkeys, which were greater than clonidine. These findings suggested that Sidiming treatment attenuated withdrawal syndrome in morphine-dependent rats and rhesus monkeys by inhibiting serum nitric oxide and its synthase.

Brain regional changes of guanine nucleotide binding protein-inhabitant 2 in acute and chronic morphine-tolerant and-dependent rats

BACKGROUND： Drug addiction involves two main central nervous systems, namely the dopamine and noradrenaline systems. These systems are primarily distributed in five brain regions： the ventral tegmental area, the nucleus accumbens, the prefrontal cortex, the hippocampus, and the locus coeruleus. OBJECTIVE： To investigate regional changes of guanine nucleotide binding protein-inhabitant 2 （Gi2） in dopaminergic and noradrenergic neurons in brains of morphine-tolerant and -dependent rats. DESIGN, TIME, AND SETTING： A randomized control study was performed at the Department of Neurobiology in the Second Military Medical University of Chinese PLA （Shanghai, China） between September 2002 and March 2004. MATERIALS： Thirty-six, healthy, male, Sprague-Dawley （SD） rats were used to establish morphine-dependent models. Morphine hydrochloride was a product of Shenyang First Pharmaceutical Factory （China）; naloxone hydrochloride was a product of Beijing Four-Ring Pharmaceutical Factory （China）; and α subunit of Gi2 antibody was offered by Santa Cruz Biotechnology, lnc （USA）. METHODS： Thirty-six SD rats were randomly divided into six groups （n = 6）： （1） acute morphine-dependent group, （2） acute abstinent group, （3） acute control group, （4） chronic morphine-dependent group, （5） chronic abstinent group, and （6） chronic control group. Rats in the acute morphine-dependent and the acute groups were injected with morphine （5 mg/kg）, one injection every two hours, for a total of eight injections. In the acute and chronic morphine-dependent rat models, morphine withdrawal syndrome was precipitated by an injection of naloxone （5 mg/kg）. Rats in the acute control group were given a peritoneal injection of physiological saline at the same administration time as the above two groups. Rats in the chronic morphine-dependent and chronic abstinent groups were injected with morphine three times per day. The administration dose on day 1 was initially 5 mg/kg at 20：00, which increased by 5 mg/kg at 8：00, 12：00, and 20：00 until day 7. On day 13, the dose continuously increased by 10 mg/kg until a chronic morphine-dependent rat model was successfully induced. Afterwards, the rats presented with withdrawal syndromes on naloxone （5 mg/kg） at 8：00 on the same day. Rats in the chronic control group were injected with physiological saline at the same time of the two chronic groups. MAIN OUTCOME MEASURES： The concentration of Gi2 protein in the five brain regions （ventral tegmental area, nucleus accumbens, prefrontal cortex, locus coeruleus, and hippocampus） was detected by immunohistochemistry. RESULTS： In the acute morphine-dependent and acute abstinent groups, Gi2 protein concentration was significantly decreased in the nucleus accumbens, compared to the acute control group （P 〈 0.01）, while no obvious changes were detected in other brain regions. In the chronic morphine-dependent and chronic abstinent groups, Gi2 protein concentration was significantly decreased in the nucleus accumbens, but significantly increased in the locus coeruleus （P 〈 0.01 ） compared to the chronic control group. CONCLUSION： Morphine dependence and tolerance may induce obvious reductions of Gi2 protein levels in the nucleus accumbens of rats. Chronic morphine dependence desensitizes the homologous neurons.

N-nitro-L-arginine Attenuates Morphine and Dihydroetorphine-induced Place Preference in Mice

Opiate dependence has become one of the most urgent problems of modernsociety. Opiate dependence involves physical and psychical dependence. Although many addicts can bedetoxified, the relapse ratio of 95% in 5 a demonstrates that opiate psychical dependence is aproblem more troublesome. It has been reported that acute and chronic administration of L- NNA canmarkedly retard the development of tolerance to physical dependence on morphine, and suppress theabstinence syndromes precipitated by naloxone in opiate dependent rodents, and even reverse theexisting morphine tolerance. However, the effect of L-NNA on the positive reinforcement ofpsychically active substances and its possible mechanism have not yet been reported. In presentstudy, the effect of L- NNA en the psychical dependence induced by opiates was evaluated on thebasis of conditioned place preference.

Expression changes of hippocampal energy metabolism enzymes contribute to behavioural abnormalities during chronic morphine treatment

Dependence and impairment of learning and memory are two well-established features caused by abused drugs such as opioids. The hippocampus is an important region associated with both drug dependence and learning and memory. However, the molecular events in hippocampus following exposure to abused drugs such as opioids are not well understood. Here we examined the effect of chronic morphine treatment on hippocampal protein expression by proteomic analyses. We found that chronic exposure of mice to morphine for 10 days produced robust morphine withdrawal jumping and memory impairment, and also resulted in a significant downregulation of hippocampal protein levels of three metabolic enzymes, including Fe-S protein 1 ofNADH dehydrogenase, dihydrolipoamide acetyltransferase or E2 component of the pyruvate dehydrogenase complex and lactate dehydrogenase 2. Further real-time quantitative PCR analyses confirmed that the levels of the corresponding mRNAs were also remarkably reduced. Consistent with these findings, lower ATP levels and an impaired ability to convert glucose into ATP were also observed in the hippocampus of chronically treated mice. Opioid antagonist naltrexone administrated concomitantly with morphine significantly suppressed morphine withdrawal jumping and reversed the downregulation of these proteins. Acute exposure to morphine also produced robust morphine withdrawal jumping and significant memory impairment, but failed to decrease the expression of these three proteins. Intrahippocampal injection of D-glucose before morphine administration significantly enhanced ATP levels and suppressed morphine withdrawal jumping and memory impairment in acute morphine-treated but not in chronic morphine-treated mice. Intraperitoneal injection of high dose of D-glucose shows a similar effect on morphine-induced withdrawal jumping as the central treatment. Taken together, our results suggest that reduced expression of the three metabolic enzymes in the hippocampus as a result of chronic morphine treatment contributes to the development of drug-induced symptoms such as morphine withdrawal jumping and memory impairment.

Brain-derived neurotrophic factor and Bcl-2 expression in rat brain areas following chronic morphine treatment

The ventral tegmental area and the locus coeruleus are associated with psychological and physical dependence of opioid addiction. To date, very little is known about brain-derived neurotrophic factor （BDNF） and Bcl-2 gene and protein changes following morphine addiction. The present study utilized immunohistochemistry and in situ hybridization techniques, which revealed that there were increased BDNF levels, but decreased Bcl-2 levels in the prefrontal cortex, locus coeruleus, hippocampus, and the ventral tegmental area during morphine-dependence formation and abstinence. However, the levels of BDNF remained unchanged, and Bcl-2 expression was increased in the nucleus accumbens. These results showed that BDNF and Bcl-2 are involved in the development of morphine dependence, and precipitation of abstinence syndrome.

Monoclonal antibody targeting mu-opioid receptor attenuates morphine tolerance via enhancing morphine-induced receptor endocytosis

Morphine is a frequently used analgesic that activates the mu-opioid receptor(MOR),which has prominent side effects of tolerance.Although the inefficiency of morphine in inducing the endocytosis of MOR underlies the development of morphine tolerance,currently,there is no effective therapy to treat morphine tolerance.In the current study,we aimed to develop a monoclonal antibody(mAb)precisely targeting MOR and to determine its therapeutic efficacy on morphine tolerance and the underlying molecular mechanisms.We successfully prepared a mAb targeting MOR,named 3A5C7,by hybridoma technique using a strategy of deoxyribonucleic acid immunization combined with cell immunization,and identified it as an immunoglobulin G mAb with high specificity and affinity for MOR and binding ability to antigens with spatial conformation.Treatment of two cell lines,HEK293T and SH-SY5Y,with 3A5C7 enhanced morphine-induced MOR endocytosis via a G protein-coupled receptor kinase 2(GRK2)/b-arrestin2-dependent mechanism,as demonstrated by immunofluorescence staining,flow cytometry,Western blotting,coimmunoprecipitation,and small interfering ribonucleic acid(siRNA)-based knockdown.This mAb also allowed MOR recycling from cytoplasm to plasma membrane and attenuated morphine-induced phosphorylation of MOR.We established an in vitro morphine tolerance model using differentiated SH-SY5Y cells induced by retinoic acid.Western blot,enzyme-linked immunosorbent assays,and siRNA-based knockdown revealed that 3A5C7 mAb diminished hyperactivation of adenylate cyclase,the in vitro biomarker of morphine tolerance,via the GRK2/b-arrestin2 pathway.Furthermore,in vivo hotplate test demonstrated that chronic intrathecal administration of 3A5C7 significantly alleviated morphine tolerance in mice,and withdrawal jumping test revealed that both chronic and acute 3A5C7 intrathecal administration attenuated morphine dependence.Finally,intrathecal electroporation of silencing short hairpin RNA illustrated that the in vivo anti-tolerance and anti-dependence efficacy of 3A5C7 was mediated by enhanced morphine-induced MOR endocytosis via GRK2/b-arrestin2 pathway.Collectively,our study provided a therapeutic mAb,3A5C7,targeting MOR to treat morphine tolerance,mediated by enhancing morphine-induced MOR endocytosis.The mAb 3A5C7 demonstrates promising translational value to treat clinical morphine tolerance.

青藤碱对吗啡依赖大鼠戒断症状及单胺类神经递质的影响

目的:观察中药单体青藤碱对吗啡依赖大鼠的作用。方法:雄性大鼠按剂量递增方法腹腔注射(ip)吗啡形成吗啡依赖模型,经给药治疗后,ip盐酸纳洛酮(1.0 mg/kg)观察戒断症状、体重及单胺类神经递质变化。结果:青藤碱能减轻大鼠戒断症状,恢复体重,降低戒断后骤增的单胺类神经递质。结论:青藤碱对吗啡依赖大鼠具有一定治疗作用,其机理可能与调节单胺类神经递质紊乱有关。

褪黑素对吗啡依赖小鼠的作用及其与脑啡肽关系的研究

目的观察褪黑素（ＭＴ）对吗啡（Ｍｏｒ）致依赖性的作用及机制分析。方法连续ｉｐＭｏｒ与纳络酮催促建立小鼠依赖模型，甩尾法，淋巴细胞增殖反应和脑啡肽（Ｍｅｔ－Ｅｎｋ）放免测定。结果Ｍｏｒ依赖组小鼠痛阈下降，跳跃次数增加，肛温降低，伴有胸腺细胞增殖能力的低下，Ｍｏｒ依赖小鼠的脑和血浆Ｍｅｔ－Ｅｎｋ亦明显降低。本文首次发现ｉｇＭＴ（３０、９０ｍｇ·ｋｇ－１×７ｄ）能明显提高依赖性小鼠的痛阈，减少跳跃次数，恢复其肛温，阻止Ｍｏｒ对淋巴细胞功能的抑制，并能维持脑、血浆Ｍｅｔ－Ｅｎｋ接近正常对照水平。结论ＭＴ具有对抗Ｍｏｒ致小鼠依赖性作用，其机制与维持内源性Ｍｅｔ－Ｅｎｋ水平有关。

四氢原小檗碱同类物缓解吗啡戒断症状作用的实验研究

目的··：观察四氢原小檗碱同类物（ＴＨＰＢｓ）对吗啡依赖小鼠和大鼠戒断症状的影响。方法··：以连续递增剂量方式ｓｃ盐酸吗啡，建立吗啡依赖小鼠和大鼠模型，ｉｐＴＨＰＢｓ２０ｍｉｎ后，用环丙羟丙吗啡（小鼠５ｍｇ·ｋｇ－１，大鼠２ｍｇ·ｋｇ－１，ｉｐ）催瘾。结果··：小鼠分别ｉｐｌ－四氢巴马汀（ｌ－ＴＨＰ，１５，３０，６０ｍｇ·ｋｇ－１）、ｌ－千金藤啶碱（ｌ－ＳＰＤ，１５，３０，６０ｍｇ·ｋｇ－１）和ｄｌ－四氢巴马汀（ｄｌ－ＴＨＰ，１５，３０，６０ｍｇ·ｋｇ－１）可显著抑制其跳台反应，降低跳台次数，减少体重下降。大鼠分别ｉｐｌ－ＴＨＰ（１０，２０，４０ｍｇ·ｋｇ－１）和ｄｌ－ＴＨＰ（１０，２０，４０ｍｇ·ｋｇ－１）能够抑制１ｈ体重下降，大大改善戒断时的行为表现，减轻腹泻和流涎，症状评分随剂量增加而下降。ｌ－ＳＰＤ抑制大鼠戒断症状作用虽无剂量依赖关系，但１０ｍｇ·ｋｇ－１却可减轻大鼠２４ｈ体重下降。结论··：ＴＨＰＢｓ可缓解吗啡依赖小鼠和大鼠戒断症状，可能具有临床应用价值。

小鼠脑内NO/NOS-cGMP信号系统与吗啡依赖形成的机制

本文观察了吗啡依赖小鼠脑组织ｃＧＭＰ含量、钙依赖性及非钙依赖性ＮＯＳ活性的变化、蛋白激酶Ａ（ｐｒｏｔｅｉｎｋｉｎａｓｅＡ，ＰＫＡ）对ＮＯＳ活性的磷酸化调节以及一氧化氮合酶（ＮＯＳ）抑制剂对吗啡依赖形成的影响。结果发现：（１）小脑、纹状体、海马及大脑皮质ｃＧＭＰ含量明显下降；（２）纹状体及大脑皮质钙依赖性ＮＯＳ活性明显升高，而ＩＰ２０（ＰＫＡ抑制剂）可抑制此变化，小脑及海马钙依赖性ＮＯＳ活性及以上各脑区非钙依赖性ＮＯＳ活性无明显变化；（３）纹状体、大脑皮质中与ＮＯＳ分子量相当的１５０ｋＤ蛋白质的体外磷酸化水平低于对照，ＩＰ２０可抑制此变化；（４）ＮＯＳ抑制剂可抑制小鼠对吗啡依赖的形成；（５）纳洛酮拮抗组小鼠未见上述变化。结果表明，吗啡依赖小鼠脑组织普遍存在ｃＧＭＰ水平下降，纹状体、大脑皮质钙依赖性ＮＯＳ活性的增加可能与吗啡依赖有关，且受ＰＫＡ对其磷酸化调节。ＮＯＳ活性增加与ｃＧＭＰ含量的下降相矛盾，提示ＮＯ／ＮＯＳ在吗啡依赖中的作用可能是通过一种不同于产生ｃＧＭＰ信号的机制进行的。

L-四氢巴马汀对吗啡依赖大鼠阿片肽含量的影响

目的 观察L 四氢巴马汀 (L THP)对吗啡依赖大鼠血浆、下丘脑 β EP和纹状体LEK含量的影响。 方法 用放射免疫法测定 β EP和LEK含量。 结果 L THP 40mg·kg-1ip可拮抗吗啡依赖大鼠 β EP释放减少的作用 (P <0 0 1)。与自然戒断组比较 ,L THP可显著加速血浆中 β EP水平的恢复 (P <0 0 5 ) ,并部分拮抗戒断 2d时下丘脑 β EP含量的下降 (P <0 0 5 ) ,对纹状体LEK含量无影响。结论 L THP能促进吗啡依赖大鼠 β EP释放 ,这可能是它抑制吗啡戒断症状的机制之一。

云南狗牙花吲哚类生物碱成分及其生物活性研究

目的:研究云南狗牙花吲哚类生物碱成分,阐明其戒毒活性的物质基础。方法:云南狗牙花茎枝粉末的95%乙醇提取浸膏经酸提碱沉后得到总生物碱(TEYA),TEYA经反复硅胶柱层析、Sephadex LH20凝胶柱层析分离纯化化学成分,波谱学分析鉴定化学结构,采用条件性位置偏爱模型对单体化合物进行活性评价。结果:分离鉴定了9个吲哚类生物成分:冠狗牙花定碱(1),伏康京碱(2),3-R-乙氧基冠狗牙花定碱(3),3-S-乙氧基冠狗牙花定碱(4),19-表-海尼山辣椒碱(5),海尼山辣椒碱(6),19-表-非洲伏康树碱(7),7-羟基冠狗牙花定碱(8),12-methoxyl-voaphylline(9)。化合物2、7对吗啡的身体依赖性和精神依赖性都有一定的防治作用。结论:化合物3、4、8、9为首次从该植物中分离得到,冠狗牙花定碱类吲哚生物碱为云南狗牙花总碱的主要活性成分。

不同时程吗啡给药大鼠部分脑区超微病理变化观察

目的:观察不同时程吗啡依赖大鼠依赖相关脑区超微病理结构变化。方法:背部皮下递增注射吗啡建立不同时程吗啡依赖大鼠模型,应用透射电镜对吗啡依赖大鼠依赖相关脑区LC、中脑导水管周围灰质、黑质、豆状核、杏仁核、海马进行观察,并与空白对照组进行比较。结果:吗啡依赖大鼠依赖相关脑区部分神经细胞肿胀或固缩,神经毡灶性水肿,有髓神经纤维髓鞘分离,线粒体肿胀、畸形,内质网扩张,多聚核糖体解聚,轴突、树突灶性水肿,细胞器稀疏,突触小泡密集并向活性区聚集。空白对照组未见异常。结论:吗啡依赖大鼠依赖相关脑区神经细胞呈缺血、缺氧性及退行性改变。

褪黑素对吗啡戒断大鼠脑内cAMP和cGMP含量的影响

目的 :观察褪黑素 (MT)对吗啡戒断大鼠不同脑区cAMP和cGMP含量的影响。方法 :以剂量递增法连续皮下注射吗啡建立吗啡依赖模型 ,采用放射免疫学方法测定脑内cAMP和cGMP的含量。结果 :(1)MT对大鼠吗啡戒断症状具有明显的抑制作用 ;(2 )与对照组比较 ,吗啡依赖大鼠的纹状体、间脑、中脑、脑桥和海马内cAMP含量显著增高 (P <0 0 5 ,P <0 0 1) ,cGMP含量显著下降 (P <0 0 5 ,P <0 0 1)。与吗啡依赖组比较 ,催促戒断大鼠海马和纹状体内cAMP的含量显著升高 (P <0 0 5 ) ,而cGMP含量显著下降 (P <0 0 5 ,P <0 0 1) ,其他部位则无明显变化 ;(3)褪黑素急性治疗可使吗啡戒断大鼠纹状体、间脑、中脑、脑桥和海马内cAMP含量明显下降 (P <0 0 5 ,P <0 0 1) ,cGMP含量明显增高 (P <0 0 5 ,P <0 0 1)。结论 :MT可显著抑制大鼠吗啡戒断反应 ,并与调节中枢cAMP和cGMP含量有关。

多巴胺对成瘾大鼠伏隔核神经元放电及形态的影响

目的从整体反射及中枢Nacc神经元的放电活动和细胞形态角度初步探讨吗啡成瘾与戒断症状产生的机制。方法实验分3个阶段:(1)观察正常大鼠Nacc神经元的性质及放电特点;(2)比较成瘾组和对照组大鼠Nacc神经元放电的区别;(3)研究多巴胺对成瘾组和对照组痛兴奋神经元(PEN)放电或痛抑制神经元(PIN)放电及甩尾反射潜伏期(TFL)或甩爪反射潜伏期(TPL)的同时影响。结果伏隔核(Nacc)中12个PEN放电的频率秒净增值增加了(158.0±9.7)%,同时TFL缩短(60.0±2.7)%;而对成瘾组13个PEN的诱发放电频率秒净增值抑制率达(43.1±6.2)%(与对照组相比较),TFL延长率为(21.0±4.5)%。DA能抑制正常大鼠Nacc中PIN电活动PIN放电频率降低,抑制率为(80.0±9.7)%。但提高成瘾大鼠的PIN放电频率,放电的净增了(40.0±0.7)%和TPL的时间延长率为(20.0±4.3)%。结论在吗啡成瘾与戒断条件下,Nacc内的多巴胺能神经元的活性发生明显改变,超微结构也发生变化。

吗啡依赖大鼠脊髓和脑干一氧化氮含量和合酶活力分析

本文检测了吗啡依赖大鼠脊髓和脑干一氧化氮合酶（ＮＯｓ）活力，一氧化氮（ＮＯ）以及ｃＧＭＰ含量。结果显示吗啡依赖大鼠脊髓ＮＯｓ活力，ＮＯ和ｃＧＭＰ含量较正常对照组降低，脑干中ＮＯｓ活力轻度降低，而ＮＯ和ｃＧＭＰ含量降低。纳洛酮激发戒断症状后大鼠脊髓和脑干ＮＯｓ活力，ＮＯ以及ｃＧＭＰ含量急剧升高。ＮＯｓ抑制剂Ｌ－Ｎ－硝基精氨酸甲酯（Ｌ－ＮＡＭＥ）处理可以抑制大鼠吗啡戒断反应，同时减少脊髓和脑干ＮＯ含量。结果表明吗啡戒断反应与脊髓和脑干的ＮＯ－ｃＧＭＰ途径的兴奋有关。

二氢埃托啡对吗啡依赖大鼠和猴的实验治疗

二氢埃托啡(DHE)能明显缓解吗啡依赖大鼠和猴用纳洛酮(Nal)催促或停用吗啡后出现的戒断症状,DHE对吗啡依赖猴替代治疗的疗效与美沙酮(Met)相当,经9d替代治疗,Met替代组动物Nal催促后仍出现一定的戒断症状,而DHE替代组动物未见戒断症状.