吗啡急性给药对大鼠伏隔核中神经甾体水平的影响

目的:观察吗啡急性给药后大鼠伏隔核中神经甾体水平的变化.方法:给3组大鼠腹腔分别注射0.5、5和20 mg/kg的盐酸吗啡,分别于给药后0.5和2 h将大鼠断头处死,分离伏隔核.经液-液萃取和固相萃取法提取脱氢表雄酮、孕烯醇酮和别孕烯醇酮,并采用高效液相色谱-质谱系统检测其含量.结果:与对照组比较,0.5 mg/kg剂量的吗啡使大鼠伏隔核中脱氢表雄酮水平显著降低,而5 mg/kg剂量的吗啡则使脱氢表雄酮水平显著升高;20 mg/kg剂量的吗啡使大鼠血浆中的别孕烯醇酮水平显著升高.结论:大鼠伏隔核中的脱氢表雄酮可能在吗啡急性给药的效应中发挥重要作用.     

吗啡依赖对大鼠伏隔核神经甾体和氨基酸递质的影响

目的　利用大鼠吗啡依赖模型,观察吗啡依赖及戒断对大鼠伏隔核中神经甾体和氨基酸类神经递质水平影响。方法　腹腔注射递增剂量的盐酸吗啡使雄性SD大鼠形成吗啡依赖,并用纳洛酮催促戒断。分离吗啡依赖和戒断大鼠的伏隔核。经液液萃取和固相萃取法提取脱氢表雄酮、孕烯醇酮、别孕烯醇酮、脱氢表雄酮硫酸酯和孕烯醇酮硫酸酯,并采用高效液相色谱质谱系统检测其含量。采用柱前衍生-电化学检测-高效液相色谱法测定甘氨酸、谷氨酸和γ氨基丁酸的含量。结果　与对照组相比,纳洛酮催促戒断时,吗啡依赖大鼠伏隔核脱氢表雄酮硫酸酯的水平下降(P<0 .05),孕烯醇酮(P<0 .01 )和谷氨酸(P<0 .05 )水平均升高。结论　吗啡戒断时大鼠伏隔核的谷氨酸系统处于兴奋状态,伏隔核中的内源性神经甾体在吗啡依赖和戒断的形成中发挥作用。     

吗啡依赖对大鼠不同脑区内神经甾体水平的影响

目的建立大鼠条件性位置偏爱(CPP)模型，探讨吗啡精神依赖对大鼠脑内神经甾体水平的影响。方法 大鼠连续10 d腹腔注射吗啡5 mg·kg^-1，诱导CPP形成。高效液相色谱-质谱法测定大鼠伏隔核、杏仁核、下丘脑和血浆中脱氢表雄酮、孕烯醇酮、别孕烯醇酮、脱氢表雄酮硫酸酯及孕烯醇酮硫酸酯的含量。结果经10 d吗啡训练后，吗啡组大鼠在伴药侧的停留时间显著长于对照组，吗啡诱导的大鼠CPP形成。与对照组相比，吗啡组大鼠下丘脑内孕烯醇酮明显降低，伏隔核和血浆中的脱氢表雄酮明显降低。结论吗啡诱导CPP形成，吗啡处理影响大鼠脑内某些神经甾体的水平，表明内源性神经甾体可能参与吗啡依赖的形成。     

酒精依赖和戒断时大鼠伏隔核、杏仁核区内神经甾体水平的变化

目的:采用♂大鼠酒精依赖模型,观察酒精依赖及戒断对大鼠伏隔核、杏仁核中不同神经甾体水平的影响。方法:通过大鼠自由饮含6%的乙醇溶液,连续42d使大鼠形成酒精依赖,并撤除酒精使其自然戒断。断头取脑分离取出伏隔核、杏仁核脑区。使用液液萃取和固相萃取两步法提取脑组织中的孕烯醇酮(PREG)、脱氢表雄酮(DHEA)、别孕烯醇酮(AP)、脱氢表雄酮硫酸酯(DHEAS)、孕烯醇酮硫酸酯(PREGS),以高效液相色谱-质谱联用法测定神经甾体含量。结果:与对照组相比,酒精依赖大鼠伏隔核DHEA,PREG,AP,DHEAS,PREGS的水平显著降低(P<0.05),杏仁核AP,PREGS的水平显著降低(P<0.05);酒精戒断6h大鼠伏隔核DHEA,DHEAS,PREGS的水平显著降低(P<0.05),杏仁核PREGS的水平显著降低(P<0.05);酒精戒断24h大鼠杏仁核DHEA的水平显著上升(P<0.05),伏隔核、杏仁核DHEAS、PREGS的水平显著下降(P<0.01)。结论:酒精依赖形成和戒断对伏隔核、杏仁核中的神经甾体水平有不同的影响,具有区域特异性。     

酒精依赖和戒断时大鼠奖赏回路不同脑区脱氢表雄酮及其硫酸酯水平的变化

目的：采用大鼠酒精依赖模型，观察酒精依赖及戒断对大鼠伏隔核、前额叶皮质、杏仁核、海马中神经甾体脱氢表雄酮（DHEA）、脱氢表雄酮硫酸酯（DHEAS）水平的影响。方法：大鼠通过自由饮含6％的乙醇溶液连续42d形成酒精依赖，并撤除酒精使自然戒断。断头取脑分离取出伏隔核、前额叶皮质、杏仁核、海马脑区。使用液一液萃取和固相萃取两步法提取脑组织中的DHEA、DHEAS，以高效液相色谱一质谱联用法测定神经甾体含量。结果：与对照组相比，酒精依赖大鼠伏隔核DHEA、DHEAS的水平显著降低（P〈0．05），海马DHEAS的水平显著升高（P〈0．05）；酒精戒断6h大鼠伏隔核DHEA、DHEAS、额叶皮质DHEAS的水平均显著降低（P〈0．05）；酒精戒断24h大鼠杏仁核DHEA、额叶皮质DHEAS水平显著上升（P〈0．05），伏隔核、杏仁核DHEAS的水平显著下降（P〈0．01）。结论：酒精依赖形成和戒断对伏隔核、前额叶皮质、杏仁核、海马中的神经甾体水平具有不同影响。     

吗啡依赖大鼠纹状体内神经甾体水平的变化

目的:探讨吗啡躯体依赖、精神依赖和戒断对♂大鼠纹状体内神经甾体水平的影响。方法:高效液相色谱-质谱法测定大鼠纹状体和血浆中脱氢表雄酮(DHEA)及其硫酸酯(DHEAS)、孕烯醇酮(PREG)及其硫酸酯(PREGS)和别孕烯醇酮(AP)的含量。结果:(1)与纳洛酮对照组比较,纳洛酮催促吗啡戒断大鼠的纹状体内PREG的含量显著升高(P<0.01);血浆中PREG、AP、DHEAS和PREGS的含量显著升高(P<0.01),而DHEA的含量显著降低(P<0.01);(2)与生理盐水对照组比较,吗啡精神依赖大鼠的纹状体内DHEA和PREG的含量显著升高(P<0.01),血浆中DHEA的水平显著降低(P<0.01)。结论:慢性吗啡处理可影响大鼠纹状体内某些神经甾体的水平,表明神经甾体可能参与吗啡依赖的形成。     

谷氨酸和γ-氨基丁酸对原代培养星形胶质细胞神经甾体合成释放的影响

目的研究氨基酸类神经递质对原代培养大鼠大脑皮质星形胶质细胞神经甾体合成释放的影响。方法采用原代培养的大鼠大脑皮质星形胶质细胞,分别加入不同浓度的谷氨酸和γ-氨基丁酸处理48h;采用固相萃取结合高效液相色谱质-谱联用分析方法提取分离和测定细胞培养液中游离型(脱氢表雄酮,DHEA;孕烯醇酮,PREG;别孕烯醇酮,AP)及结合型神经甾体(脱氢表雄酮硫酸酯,DHEAS;孕烯醇酮硫酸酯,PREGS)。结果与生理盐水对照组比较,谷氨酸处理使PREG和PREGS水平明显下降,DHEAS水平明显升高;γ-氨基丁酸处理使PREG水平明显降低,AP水平增加。结论谷氨酸和γ-氨基丁酸两种神经递质对原代培养的星形胶质细胞PREG合成释放均呈抑制作用;谷氨酸对DHE-AS、γ-氨基丁酸对AP的合成释放分别呈现明显促进作用;高剂量的谷氨酸还可以抑制PRGES的合成和释放。     

吗啡依赖和复吸时大鼠脑内神经甾体水平的变化

目的探讨吗啡精神依赖和复吸对大鼠脑内神经甾体水平的影响。方法采用条件性位置偏爱(CPP)实验,吗啡诱导大鼠CPP形成,足底电击应激诱发CPP重建,高效液相色谱-质谱法测定大鼠额叶皮质、海马及血浆中孕烯醇酮(PREG)及其硫酸酯(PREGS)、别孕烯醇酮(AP)、脱氢表雄酮(DHEA)及其硫酸酯(DHEAS)的含量。结果5 mg.kg-1吗啡训练10 d诱导大鼠产生了稳定的CPP,间歇足底电击有效诱发CPP的重建。与对照组比较,吗啡CPP形成时,大鼠额叶皮质内DHEA、PREG水平升高(P<0.05),海马内DHEA水平降低(P<0.05);与吗啡消退组比较,足底电击诱发CPP重现时,大鼠额叶皮质内PREG水平降低(P<0.01),而海马内PREG水平升高(P<0.05)。结论大鼠额叶皮质和海马内神经甾体水平的变化可能与吗啡依赖和复吸有关。     

孕酮对大鼠吗啡位置偏爱效应及氨基酸递质水平的影响

目的：观察孕酮对吗啡位置偏爱效应及脑内氨基酸类神经递质水平的影响。方法：采用大鼠条件性位置偏爱（CPP）模型，高效液相色谱-电化学法测定大鼠伏隔核及腹侧被盖区中的谷氨酸（GLU）和γ-氨基丁酸（GABA）的含量。结果：吗啡可诱导大鼠产生稳定的CPP效应；孕酮本身不产生CPP效应，但能抑制吗啡诱导的CPP效应。与对照组比较，吗啡诱导的CPP形成时，大鼠伏隔核中的GLU、GABA水平和VTA中的GLU水平均显著降低（P〈0．05）。与吗啡组比较，合用孕酮均可使大鼠伏隔核中的GABA水平显著升高（P〈0．01）。结论：孕酮可有效抑制吗啡诱导的CPP效应，其机制可能与阻止吗啡降低伏隔核GABA的水平有关。     

吗啡成瘾和应激诱导复发的大鼠脑内神经甾体水平的变化

目的 观察大鼠吗啡成瘾及应激诱导成瘾复发是否与脑组织神经甾体水平的变化有关。方法 给大鼠注射吗啡（5 mg·kg^-1·d^-1，ip, 18：00～20：00）并在条件性位置偏爱(CPP)箱中训练，每日1次，连续10 d，最后1次给药后24 h测试大鼠是否产生CPP。再经过7 d的自然消退期后，给予足底电击(0.5 mA, 0.5 s, 间隔40 s, 15 min)诱发大鼠CPP复发，电击后2 h 进行CPP测试。测试后立即取样，取样时间18：00～20：00，气相色谱-质谱联用技术测定大鼠脑组织神经甾体。结果 给予吗啡并训练10 d，大鼠形成明显的CPP，同时脑组织内神经甾体孕烯诺龙和别孕烯诺龙水平显著升高。经过7 d的自然消退后再给予足底电击可诱发大鼠CPP复发，脑组织神经甾体脱氢表雄酮和硫酸脱氢表雄酮水平显著升高。结论 大鼠吗啡成瘾及应激诱导成瘾复发过程可能与脑组织内源性神经甾体水平有关。     

Effects of morphine dependence and withdrawal on levels of neurosteroids in rat brain

AIM: To investigate the effects of morphine dependence and withdrawal on the concentrations of neurosteroids in rat brain. METHODS: A method of simultaneous quantification of neurosteroids by gas chromatography-mass spectrometry (GC-MS) had been established. RESULTS: The chronic morphine administration (ip) resulted in a marked decrease in the brain concentrations of pregnenolone (PREG), progesterone (PROG), and pregenenolone sulfate (PREGS) in rats killed 6 h after the last treatment. In contrast, there were no significant effects of morphine dependence on the brain concentrations of allopregnanolone (AP), dihydroepiandrosterone (DHEA), and dihydroepiandrosterone sulfate (DHEAS). Naloxone-induced withdrawal produced a significant increase in the concentrations of PREG, PROG, AP, DHEA, PREGS, and DHEAS as compared with the control group. CONCLUSION: Morphine dependence and withdrawal affected the concentrations of neurosteroids in rat brain, which suggests that endogenous neurosteroids in brain might be     

Effects of dextromethorphan on dopamine release in the nucleus accumbens: Interactions with morphine

Dextromethorphan has been reported to decrease the self-administration of several drugs of abuse, including morphine, methamphetamine, cocaine, and nicotine. Most drugs of abuse increase extracellular levels of dopamine (DA) in the shell of the nucleus accumbens. The effects of dextromethorphan on DA release in the nucleus accumbens of nai;ve rats and of rats treated acutely and chronically with morphine were studied using in vivo microdialysis. DA dialysate levels were evaluated by high-performance liquid chromatography with electrochemical detection. Acute morphine (5 mg/kg i.p.) treatment increased the levels of DA in the nucleus accumbens to approximately 175% of basal levels. Chronic morphine (20 mg/kg i.p. daily for 5 days) increased DA release in the nucleus accumbens to 250% of basal levels. Acute treatment with dextromethorphan (20 or 30 mg/kg s.c.) alone did not alter nucleus accumbens DA levels. Pretreatment with dextromethorphan (20 mg/kg s.c., 20 min prior) potentiated the effects of acute morphine, while attenuating the effects of chronic morphine on nucleus accumbens DA levels. These results with dextromethorphan suggest that the mechanism mediating the effects of dextromethorphan on drug self-administration involves modulation of the dopaminergic mesolimbic pathway.     

Nitric oxide in the nucleus accumbens is involved in retrieval of inhibitory avoidance memory by nicotine

In the present study, the possible effect of nitric oxide agents injected into the nucleus accumbens (NAc) in the presence or absence of nicotine on morphine state-dependent memory in adult male Wistar rats was investigated. As a model of memory, a step-through type inhibitory avoidance task was used. Post-training injection of morphine (4 and 6 mg/kg) dose dependently induced the impairment of memory retention. Administration of morphine (4 and 6 mg/kg) before retention induced state-dependent retrieval of the memory acquired under post-training morphine (6 mg/kg) influence. Injection of nicotine before retention (0.25 and 0.5 mg/kg) alone and nicotine (0.1, 0.25 and 0.5 mg/kg) plus an ineffective dose of morphine (2 mg/kg) reversed the post-training morphine-induced memory impairment. The amnesia elicited by morphine (6 mg/kg) was also prevented by pre-retention intra-NAc administration of a nitric oxide synthase (NOS) inhibitor, l-NAME (0.24 μg/rat, intra-NAc). Interestingly, an ineffective dose of nicotine (0.1 mg/kg) in combination with low doses of l-NAME (0.06 and 0.12 μg/rat, intra-NAc) synergistically improved memory performance impaired by morphine given after training. It is important to note that intra-NAc administration of l-NAME before retention impaired memory retrieval by itself. In contrast, pre-retention administration of l-arginine, a nitric oxide (NO) precursor (0.25 and 0.5 μg/rat, intra-NAc), which had no effect alone, prevented the nicotine reversal of morphine effect on memory. The results suggest a possible role for nitric oxide of nucleus accumbens in the improving effect of nicotine on the morphine-induced amnesia and morphine state-dependent memory.     

Agmatine modulates neuroadaptations of glutamate transmission in the nucleus accumbens of repeated morphine-treated rats

It has been proved that agmatine inhibits opioid dependence, yet the neural mechanism remains unclear. In the present study, the effect of agmatine on the neuroadaptation of glutamate neurotransmission induced by morphine dependence, including changes of the extracellular glutamate level and glutamate receptors in the nucleus accumbens was investigated.We found that agmatine (2.5–20 mg/kg, s.c.) inhibited development of morphine dependence, which was consistent with our previous report. In rats repeatedly treated with morphine, the glutamate level in the nucleus accumbens dialysate was markedly increased after naloxone-precipitated withdrawal. When agmatine (20 mg/kg, s.c.) was co-pretreated with morphine or was applied before naloxone-precipitated withdrawal, this elevation of the extracellular glutamate level was inhibited. In the synaptosome model, repeated morphine treatment and naloxone precipitation induced an increase in glutamate release, while agmatine (20 mg/kg, s.c.) co-pretreated with morphine reversed the increase of glutamate release. However, neither morphine or agmatine treatment alone nor morphine and agmatine co-administration had any influence on [3H]-glutamate uptake. It indicated that the elevation of the glutamate level in the nucleus accumbens might be caused by the increase of glutamate release of synaptosome in the withdrawal conditions of morphine-dependent rat. Furthermore, agmatine concomitant treatment with morphine entirely abolished the up-regulation of the NR1 subunit of N-methyl-d-aspartate (NMDA) receptors in the nucleus accumbens in repeated morphine-treated rats.Taken together, the present study demonstrated that agmatine could modulate the neuroadaptations of glutamate transmission in the nucleus accumbens in the case of morphine dependence, including modulating extracellular glutamate concentration and NMDA receptor expression.     

Acute administration of clozapine, thioridazine and metoclopramide increases extracellular DOPAC and decreases extracellular 5-HIAA, measured in the nucleus accumbens and striatum of the rat using in vivo voltammetry

Changes in the extracellular levels of dihydroxyphenylacetic acid (DOPAC) and 5-hydroxy-indoleacetic acid (5-HIAA) after acute administration of clozapine (50 mg/kg s.c.), thioridazine (20 mg/kg s.c.) and metoclopramide (5 mg/kg s.c.), were monitored using in vivo voltammetry with micro-carbon electrodes implanted in the nucleus accumbens and striatum of the rat anaesthetised with halothane/N2O. Both clozapine and thioridazine increased extracellular levels of DOPAC in the striatum and the nucleus accumbens. The maximum increases with clozapine were 60% and 86% in the nucleus accumbens and striatum and 44% and 55% with thioridazine. Both neuroleptics also decreased the extracellular level of 5-HIAA in these regions of the brain. Metoclopramide increased the extracellular level of DOPAC in the nucleus accumbens (42%) and the striatum (57%) and significantly decreased the level of 5-HIAA in the nucleus accumbens. These results suggest that the two so-called atypical neuroleptics, clozapine and thioridazine, do not have selective effects on the metabolism of dopamine in vivo in the nucleus accumbens after acute administration. Furthermore, neuroleptic-induced increases in dopamine metabolism are accompanied by reciprocal decreases in 5-hydroxytryptamine metabolism in vivo.     

The role of nitric oxide within the nucleus accumbens on the acquisition and expression of morphine-induced place preference in morphine sensitized rats

In the present study, the effects of intra-accumbal administration of L-arginine, a nitric oxide precursor, and N(G)-nitro-L-arginine methyl-ester (L-NAME), a nitric oxide synthase inhibitor, on the acquisition and expression of morphine-induced place conditioning in morphine-sensitized rats were studied. Subcutaneous (s.c.) administration of morphine (2.5, 5 and 7.5 mg/kg) induced conditioned place preference. Repeated pretreatment of morphine (5 mg/kg, i.p.) followed by 5 days without drug treatment, increased conditioning response induced by morphine (0.25, 0.5 and 0.75 mg/kg). Intra-accumbal (intra-nucleus accumbens; 1 microg/rat) administration of L-arginine (0.3, 1 and 3 microg/rat) significantly increased or reduced the acquisition of morphine place conditioning in non-sensitized and sensitized rats respectively. However, the drug reduced expression of place conditioning by morphine in sensitized animals. Intra-nucleus accumbens injections of L-NAME (0.3, 1 and 3 microg/rat) reduced the acquisition and expression of morphine place conditioning in the sensitized animals. The results indicate that nitric oxide (NO) within the nucleus accumbens is involved in the acquisition and expression of morphine place conditioning in morphine-sensitized rats.