吗啡精神依赖大鼠VTA-NAc-PFC神经环路谷氨酸含量和NR2B表达的变化

目的 观察吗啡诱导条件性位置偏爱大鼠中脑腹侧被盖区-伏核-前额叶皮质(VTA-NAc-PFC)神经环路各核团谷氨酸递质含量和N-甲基-D-天冬氨酸受体亚基NR2B表达的变化,从受体前和受体层面探讨该环路中通过谷氨酸能系统的阿片类精神依赖机制.方法 筛选出合格大鼠32只并按随机数字表法分为生理盐水对照组和吗啡条件性位置偏爱模型组(模型组),模型组采用吗啡剂量递增法建立大鼠条件性位置偏爱模型,分别用比色法和免疫组化染色检测中脑腹侧被盖区、伏核和前额叶皮质内谷氨酸含量和NR2B的表达.结果 与生理盐水对照组比较,模型组大鼠在白箱的停留时间明显延长,VTA-NAc-PFC神经环路各核团谷氨酸含量明显增高,NR2B平均吸光度值明显增加,差异均有统计学意义(P<0.05).结论 VTA-NAc-PFC神经环路谷氨酸递质含量及其受体亚基NR2B表达水平上调在吗啡精神依赖形成中发挥重要作用.

Abstract：

Objective To explore the mechanism of opioid-psychic dependence involving the aspects of pre-receptor and receptor by observing the changeable expressions of glutamate neurotransmitter and NR2B of N-methyl-D-aspartic acid (NMDA) receptor in the neuroanatomical circuit of ventral temental area, nucleus accumbens and prefrontal cortex (VTA-Nac-PFC) of rats subjected to morphine-induced conditioned place preference (CPP). Methods The models of CPP were validated by escalating doses of morphine in rats (n=16). The colorimetry and immunohistochemistry ways were applied to detect the contents of glutamic acid and the expression level of NR2B in VTA, Nac and PFC. Results As compared with those in the control group physiological saline), the prolonged detention time of white compartment in the model group was notably observed (P<0.05), and increased content of glutamic acid and expression level of NR2B in fields of VTA, Nac and PFC in the model group were significantly detected (P<0.05). Conclusion Increased level of giutamic acid and expression level of NR2B in nuroanatomieal circuit of VTA, Nac and PFC could play key roles in inducing morphine-psychic dependent rats.     

吗啡精神依赖大鼠VTA-NAc-PFC神经环路谷氨酸含量和NR2B表达的变化

目的 观察吗啡诱导条件性位置偏爱大鼠中脑腹侧被盖区-伏核-前额叶皮质(VTA-NAc-PFC)神经环路各核团谷氨酸递质含量和N-甲基-D-天冬氨酸受体亚基NR2B表达的变化,从受体前和受体层面探讨该环路中通过谷氨酸能系统的阿片类精神依赖机制.方法 筛选出合格大鼠32只并按随机数字表法分为生理盐水对照组和吗啡条件性位置偏爱模型组(模型组),模型组采用吗啡剂量递增法建立大鼠条件性位置偏爱模型,分别用比色法和免疫组化染色检测中脑腹侧被盖区、伏核和前额叶皮质内谷氨酸含量和NR2B的表达.结果 与生理盐水对照组比较,模型组大鼠在白箱的停留时间明显延长,VTA-NAc-PFC神经环路各核团谷氨酸含量明显增高,NR2B平均吸光度值明显增加,差异均有统计学意义(P<0.05).结论 VTA-NAc-PFC神经环路谷氨酸递质含量及其受体亚基NR2B表达水平上调在吗啡精神依赖形成中发挥重要作用.     

吗啡精神依赖大鼠VTA-NAc-PFC神经环路谷氨酸含量和NR2B表达的变化

目的 观察吗啡诱导条件性位置偏爱大鼠中脑腹侧被盖区-伏核-前额叶皮质(VTA-NAc-PFC)神经环路各核团谷氨酸递质含量和N-甲基-D-天冬氨酸受体亚基NR2B表达的变化,从受体前和受体层面探讨该环路中通过谷氨酸能系统的阿片类精神依赖机制.方法 筛选出合格大鼠32只并按随机数字表法分为生理盐水对照组和吗啡条件性位置偏爱模型组(模型组),模型组采用吗啡剂量递增法建立大鼠条件性位置偏爱模型,分别用比色法和免疫组化染色检测中脑腹侧被盖区、伏核和前额叶皮质内谷氨酸含量和NR2B的表达.结果 与生理盐水对照组比较,模型组大鼠在白箱的停留时间明显延长,VTA-NAc-PFC神经环路各核团谷氨酸含量明显增高,NR2B平均吸光度值明显增加,差异均有统计学意义(P<0.05).结论 VTA-NAc-PFC神经环路谷氨酸递质含量及其受体亚基NR2B表达水平上调在吗啡精神依赖形成中发挥重要作用.     

吗啡依赖大鼠脑内相关脑区CREB mRNA的表达

目的　观察吗啡依赖和戒断时大鼠脑内转录因子CREBmRNA的变化。方法　采用逆转录PCR(RT PCR)方法 ,对CREBmRNA在吗啡依赖和戒断时大鼠脑内与阿片类物质依赖有关的前额叶皮质、海马、伏隔核和新纹状体等脑区的表达进行观察。结果　吗啡依赖和戒断时前额叶皮质以及吗啡戒断时新纹状体CREBmRNA的光密度值高于对照组 ,海马、伏隔核等处无改变。结论　吗啡依赖和戒断时CREBmRNA在某些脑区的表达升高 ,提示CREB可能与阿片类物质依赖的形成有关。     

毁损双侧伏隔核对大鼠吗啡条件性位置偏爱复燃的影响

目的探讨毁损双侧伏隔核对小剂量吗啡诱导大鼠条件性位置偏爱复燃的影响。方法设置毁损组、假毁损组及空白对照组(n=10),建立大鼠吗啡条件性位置偏爱模型,消退后采用立体定向下直流电(10mA,30s)毁损双侧伏隔核,分别在术后3d、10d、30d给予小剂量吗啡(2.5mg/kg)诱导复燃,观察记录各组大鼠条件性位置偏爱得分,采用方差分析及均数间多重比较进行统计学分析。结果条件性位置偏爱模型建立成功后,经消退各组位置偏爱得分间差异无统计学意义(P>0.05);毁损术后各时间点吗啡诱导复燃时,毁损组均较假毁损组的位置偏爱得分低(P<0.05),而毁损组各时间点间位置偏爱得分差异无统计学意义(P>0.05)。结论毁损双侧伏隔核可以抑制小剂量吗啡诱导的复燃,且此作用至少可维持30d。     

海人酸致痫大鼠海马细胞外氨基酸类神经递质的变化

目的 分析海马细胞外氨基酸递质在癫痫发生中的作用,探讨海人酸致痫模型大鼠癫痫发生的机制.方法 应用立体定向方法建立海人酸大鼠颞叶癫痫模型,观察大鼠行为学和电生理变化,应用电镜观察大鼠海马超微结构,应用微透析获取大鼠海马细胞外液,高压液相色谱法测定透析液中的兴奋性氨基酸谷氨酸、抑制性氨基酸牛磺酸及γ-氨基丁酸的含量.结果 海人酸注射后大鼠出现典型的颞叶癫痫发作,皮层脑电显示痫性发作,电镜显示兴奋性神经递质增加,高效液相色谱分析显示海马细胞外谷氨酸、牛磺酸和γ-氨基丁酸含量明显高于对照组(P＜0.05),虽然谷氨酸、γ-氨基丁酸都升高,而谷氨酸升高的更明显.结论 兴奋性氨基酸与抑制性氨基酸的失衡在海人酸致痫大鼠模型的癫痫发生过程中发挥重要作用,是癫痫发生的原因之一.     

大鼠慢性吗啡处理后不同时间部分脑区腺苷酸环化酶Ⅷ基因表达的变化

目的　研究慢性吗啡处理的大鼠停药后不同时间部分脑区腺苷酸环化酶Ⅷ (ACⅧ )基因表达水平的变化。方法　将 2 4只雄性Sprague Dawley大鼠随机等分为吗啡依赖组 (吗啡组 ;在大鼠腹腔内注射盐酸吗啡 ,2次 /d ;起始剂量为 5mg/kg ,逐日递增 5mg ,至第 10天为 5 0mg/kg)及生理盐水对照组 (对照组 ;用相同方式注射同体积的生理盐水 ) ,于末次注射后 3h及 72h处死 (每组每时间点各 6只 ) ,取中脑腹侧被盖区 (VTA)、伏隔核 (NAc)、中脑导水管灰质 (PAG)、杏仁核 (AMG)、海马CA1区 (HIPCA1)等脑组织。利用组织原位杂交技术检测各脑区ACⅧmRNA的吸光度 (A)值 ,并作同期平行比较。结果　 (1)末次注射 3h ,吗啡组NAc、PAG、AMG、HIPCA1的A值 (依次为 0 2 4 8±0 0 0 7、0 2 5 6± 0 0 11、0 2 6 8± 0 0 2 0、0 2 79± 0 0 16 )高于对照组 (依次为 0 2 34± 0 0 11、0 2 4 0±0 0 11、0 2 4 0± 0 0 11、0 2 5 1± 0 0 13;P <0 0 5～ 0 0 1) ,两组VTA的A值的差异无显著性 (P >0 0 5 )。 (2 )末次注射 72h ,吗啡组NAc、AMG的A值 (0 2 4 3± 0 0 0 7、0 2 5 2± 0 0 0 7)高于对照组(0 2 2 5± 0 0 12、0 2 2 5± 0 0 11;P <0 0 1) ,VTA、PAG的A值 (0 2 30± 0 0 10、0 2 2 8± 0 0     

吗啡成瘾对大鼠伏隔核神经元自发放电的影响

目的 研究吗啡成瘾对大鼠伏隔核电生理的影响及静脉吗啡注射对吗啡成瘾大鼠伏隔核神经元自发放电的影响探讨伏隔核在吗啡成瘾过程中的作用.方法 通过连续14日递增腹腔吗啡注射,建立急性大鼠吗啡成瘾模型,通过玻璃微电极记录吗啡依赖大鼠伏隔核单细胞细胞外放电,观察吗啡成瘾及静脉注射吗啡对大鼠伏隔核神经元放电的影响.结果 与生理盐水组相比,吗啡依赖组大鼠伏隔核神经元单位自发放电的频率分布组间差异显著(P<0.05),放电形式无明显差异.吗啡依赖大鼠伏隔核神经元放电频率静脉注射吗啡前为14.40±4.92Hz,静脉注射吗啡后降为4.10±2.65Hz.结论 吗啡成瘾对大鼠伏隔核神经元自发放电有影响,吗啡可以显著抑制吗啡成瘾大鼠的伏隔核神经元放电,伏隔核在吗啡成瘾过程具有重要作用.     

环磷酸腺苷反应元件结合蛋白在吗啡依赖及戒断大鼠脑区的表达

目的　研究吗啡依赖及吗啡戒断时环磷酸腺苷反应元件结合蛋白 (CREB)在大鼠脑内的表达。方法　将 1 5只雄性Sprague Dawley大鼠随机分为正常对照组、吗啡依赖组和吗啡戒断组 ,每组各 5只。于大鼠背部皮下注射吗啡 ,第 1天注射 2 0mg/kg ,逐日递增剂量 ,至第 5天达 1 0 0mg/kg ,形成大鼠吗啡依赖模型。吗啡戒断组大鼠在末次注射吗啡后 1 6h皮下注射纳洛酮 1mg/kg。采用免疫印迹法观察各组大鼠的前额叶皮质、伏隔核和海马等脑区CREB的表达。结果　 (1 )在前额叶皮质 ,吗啡依赖组和吗啡戒断组CREB的含量 (为相对光密度值 )分别为 [(1 31± 1 1 ) % ]和 [(1 33± 1 5) % ] ,均高于正常对照组 [(1 0 0± 1 4 ) % ] ,差异有显著性 (P <0 0 5) ;(2 )在伏隔核 ,三组CREB的差异无显著性(P >0 0 5) ;(3)在海马 ,吗啡戒断组CREB的含量 [(1 4 1± 1 8) % ]高于正常对照组 [(1 0 0± 1 4 ) % ] ,差异有非常显著性 (P <0 0 1 )。结论　大鼠处于吗啡依赖和戒断时CREB的表达在前额叶皮质和海马发生改变 ,表明多个脑区CREB表达的调节参与了阿片类物质依赖的形成     

中枢谷氨酸能系统与吗啡依赖

本文综述了谷氨酸、谷氨酸受体及其拮抗剂对吗啡位置偏爱、戒断综合征、吗啡依赖部分相关基因表达的影响。     

Changes in the expression of glial glutamate transporters in the rat brain accompanied with morphine dependence and naloxone-precipitated withdrawal

The expression of mRNAs for the glial glutamate transporters, GLT-1 and GLAST, in the rat brain accompanied with morphine dependence and naloxone-precipitated withdrawal was investigated by Northern blot analysis. The expression of GLT-1 mRNA was significantly decreased in the striatum and thalamus of morphine-dependent rats, and significantly increased in the striatum 2 h after the naloxone-precipitated withdrawal, compared with that of naive rats. On the other hand, there were no significant changes in GLAST mRNA level in any brain region. These results suggest the involvement of GLT-1 in the development of morphine dependence and the expression of morphine withdrawal.     

Distribution of morphine in brain regions, spinal cord and serum following intravenous injection to morphine tolerant rats

In order to determine the possible contribution of altered distribution of morphine in the morphine tolerance process, the distribution of morphine was studied in brain regions and spinal cord, following its intravenous administration. Male Sprague-Dawley rats were made tolerant to morphine by implanting 6 morphine pellets, each containing 75 mg of morphine base, for 7 days. Seventy-two hours after the removal of the pellets, a time when serum morphine levels were negligible or absent and yet tolerance to the pharmacological effects of morphine was present, morphine (10 mg/kg, i.v.) was injected in placebo and morphine pellet implanted rats. At various times (5, 30, 60, 120 and 360 min) after the injection of morphine, brain regions (hypothalamus, cortex, hippocampus, midbrain, pons and medulla, striatum and amygdala), spinal cord and serum were collected. The level of morphine in the tissues was determined by using a highly sensitive and specific radioimmunoassay (RIA) method. Five minutes after morphine injection, the concentration of morphine was the highest in the hypothalamus and the lowest in amygdala. The concentration of morphine in hypothalamus, pons and medulla, hippocampus and midbrain of morphine tolerant rats was smaller than in placebo pellet implanted rats. The tissue to serum ratio of morphine in the hypothalamus, hippocampus, striatum, midbrain and cortex were also smaller in morphine tolerant than in non-tolerant rats. The concentration of morphine in brain regions with time did not exhibit linearity. At other time intervals like 30 and 60 min, the concentration of morphine in several brain regions and spinal cord was significantly higher in morphine tolerant than in non-tolerant rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

吗啡依赖及戒断对大鼠强啡肽原mRNA表达的影响

目的　研究吗啡依赖形成及戒断对大鼠强啡肽原mRNA表达的影响。方法　将 18只Sprague Dawley雄性大鼠随机分为吗啡依赖组、吗啡戒断组和空白对照组 ,每组 6只。采用皮下注射吗啡建立大鼠吗啡依赖模型 ,初剂量为 10mg/kg ,以后每天增加 5mg/kg ,3次 /d ,连续 6天。应用放射性3 2 磷标记的三磷酸脱氧胞苷掺入标记探针法进行Northern印迹杂交技术检测三组大鼠强啡肽原mRNA的表达水平。结果　 (1)连续 6天给予吗啡 ,吗啡依赖组大鼠下丘脑 (2 3 88± 1 6 2 )、纹状体(19 87± 2 0 3)及脊髓 (13 36± 1 4 6 )的强啡肽原mRNA相对含量分别低于对照组 (分别为 34 36±1 4 6、31 2 4± 2 83和 2 7 6 0± 2 89;均P <0 0 1) ,海马 (2 9 6 7± 3 2 3)强啡肽原mRNA相对含量高于对照组 (2 5 87± 1 74 ,P <0 0 5 ) ;(2 )给予纳洛酮处理 6 0min后 ,下丘脑 (10 2 2± 1 2 2 )、纹状体(5 90± 0 84 )、脊髓 (2 99± 0 4 8)强啡肽原mRNA的相对含量低于吗啡依赖组 (均P <0 0 1) ,而垂体强啡肽原mRNA(2 6 72± 1 79)却高于吗啡依赖组 (11 6 0± 2 2 4 ,P <0 0 1)。结论　慢性给予吗啡可影响大鼠强啡肽原mRNA的表达 ,从而参与吗啡依赖形成和戒断反应。     

Changes in extracellular levels of amygdala amino acids in genetically fast and slow kindling rat strains

A neurochemical basis for many of the epilepsies has long been suspected to result from an imbalance between excitatory and inhibitory neurotransmitter mechanisms. Data supporting changes in extrasynaptic amino acid levels during epileptogenesis, however, remain controversial. In the present study, we used in vivo microdialysis to measure the levels of extracellular GABA (gamma-aminobutyric acid) and glutamate during seizure development in rats with a genetic predisposition for (Fast), or against (Slow), amygdala kindling. Dialysates were collected from both amygdalae before, during, and up to 12 min after a threshold-triggered amygdala afterdischarge (AD). One hour later, samples were again collected from both amygdalae in response to a hippocampal threshold AD. Daily amygdala kindling commenced the next day but without dialysis. After the rats were fully kindled, the same protocol was again employed. Amino acid levels were not consistently increased above baseline with triggered seizures in either strain. Instead, before kindling, a focal seizure in the Slow rats was associated with a large decrease in GABA in the non-stimulated amygdala, while amino acid levels in the Fast rats remained near baseline in both amygdalae. Similar results were seen after kindling. By contrast, before and after kindling, hippocampal stimulation caused large decreases in all amino acid levels in both amygdalae in both strains. These data suggest that, in response to direct stimulation, extracellular amino acid concentrations remain stable in tissues associated with either greater natural (Fast) or induced (kindled Fast/Slow) excitability, but are lowered with indirect stimulation (hippocampus) and/or low excitability.     

Changes in cortical extracellular levels of energy-related metabolites and amino acids following concussive brain injury in rats

The aim of this study was to measure extracellular chemical changes in the cerebral cortex in response to compression contusion trauma in rats. Energy-related metabolites (i.e., lactate, pyruvate, adenosine, inosine, and hypoxanthine) and amino acids were harvested from the extracellular fluid (ECF) using microdialysis and analyzed by high-performance liquid chromatography. The measurements were performed in cortical tissue, where neuronal injury occurs in this model. The severity of the trauma was varied by using different depths of impact: mild trauma, 1.5 mm; severe trauma, 2.5 mm. The trauma induced a dramatic increase in the ECF levels of energy-related metabolites that was conditioned by the severity of the insult. The ECF level of taurine, glutamate, aspartate, and gamma-aminobutyric acid (GABA) also rose markedly, while other amino acids did not change significantly. The results suggest that the trauma induced a transient, profound focal disturbance of energy metabolism in the cortical tissue, probably as a result of mechanically induced disruption of ion homeostasis and reduced blood flow in combination. The data support the potential role of glutamate and aspartate as mediators of traumatic brain injury. However, the concomitantly released adenosine, GABA, and taurine may be protective and ameliorate excitotoxicity. In analogy with the reported cumulative damaging effects of repeated ischemic insults, the observed ECF changes may help explain the vulnerability of traumatized brain tissue to secondary ischemia.     

Effects of handling on extracellular levels of glutamate and other amino acids in various areas of the brain measured by microdialysis

Upon a physiological and pharmacological challenge, the responsiveness of extracellular glutamate levels in the prefrontal cortex, ventral tegmental area and locus coeruleus were studied using microdialysis. A 10-min handling period was used as a mild stressful stimulus. In all three brain areas, handling induced an immediate and short-lasting increase in glutamate levels, but the responses were highly variable. Only in the ventral tegmental area and the locus coeruleus, but not in the prefrontal cortex, the increases were significantly different from basal values. In rats with relatively low basal glutamate levels, both in the ventral tegmental area and locus coeruleus, handling had a more pronounced effect on glutamate levels than in rats with high basal levels, although in some rats with relatively low basal levels of glutamate, handling had hardly any effect. Potassium stimulation also induced variable responses in all three brain areas. Again, relatively low basal glutamate levels were more responsive to the stimulation than higher basal values, although there appeared to be a lower limit. These data suggest that relatively high basal levels contain sources of glutamate that mask the neuronal pool of glutamate and are therefore less responsive to physiological or pharmacological stimulation. However, this interpretation was questioned by the findings that basal levels and handling-induced increases in glutamate levels were found to be (partly) TTX-independent. As carrier-mediated release as a possible non-exocytotic release mechanism has only been described in vivo under pathological conditions, it seems plausible to ascribe TTX-independent glutamate increases to aspecific, non-neuronal processes. This interpretation was further supported by the observation that in all three brain areas, other amino acids, i.e., aspartate, taurine, glutamine, serine, alanine and glycine also increased upon handling in a very similar way as glutamate did. Thus, these results question a direct correlation between stimulated extracellular glutamate levels induced by handling and measured by microdialysis and glutamatergic neurotransmission.     

Increasing of intrathecal CSF excitatory amino acids concentration following morphine challenge in morphine-tolerant rats

Excitatory amino acids (EAAs) are involved in the development of opioid tolerance. The present study reveals that an increasing of CSF EAAs concentration might be responsible for the losing of morphine's antinociceptive effect in morphine tolerant rats. Male Wistar rats were implanted with two intrathecal (i.t.) catheters and one microdialysis probe, then continuously infused i.t. for 5 days with saline (1 microl/h; control group), morphine (15 micrograms/h), the NMDA antagonist, MK-801 (5 micrograms/h), or morphine (15 micrograms/h) plus MK-801 (5 micrograms/h). Each day, tail-flick responses were measured; in addition, CSF dialysates were collected and CSF amino acids measured by high performance liquid chromatography using a fluorescence detector. Morphine started to lose its analgesic effect on day 2 and this effect was overcome by MK-801. The AD(50) (AD: analgesic dose) was 1.33 micrograms in control animals, 83.83 micrograms in morphine-tolerant rats (a 63-fold shift), and 11.2 micrograms (a 8.4-fold shift) in rats that had received MK-801 plus morphine. No significant differences were observed in CSF amino acid release between the groups from day 1 to day 5. On day 5, after basal dialysate collection, a 10-micrograms challenge of morphine was administered i.t., and CSF samples collected over the next 3 h. After morphine challenge, morphine-tolerant rats showed a significant increase in the release of glutamate and aspartate (131+/-9.5% and 156+/-12% of basal levels, respectively), and no antinociceptive effect in the tail-flick latency test, while MK-801/morphine co-infused rats showed no increase in morphine-induced EAA release and a partial antinociceptive effect (MPE=40%). The present study provides direct evidence for a relationship between EAA release and a lack of an antinociceptive response to morphine, and shows that the NMDA antagonist, MK-801, attenuates both of these effects.     

3-硝基丙酸诱发肌张力障碍大鼠的相关脑区细胞外神经递质变化

目的 研究3-硝基丙酸(3-NP)诱发肌张力障碍大鼠相关核团的神经递质变化.方法 24只SD大鼠随机分为对照组和实验组,每组12只.实验组大鼠尾壳核注射3-NP4000 μmol,对照组尾壳核注射生理盐水4μl,3 d后对两组大鼠进行行为学评分,然后对尾壳核、苍白球内侧、苍白球外侧和丘脑底核行微透析,用高效液相色谱法测定透析液中的神经递质含量.结果 实验组尾壳核天冬氨酸及谷氨酸较对照组明显增加(P＜0.05),而甘氨酸及γ-氨基丁酸较对照组明显减少(P＜0.01);苍白球内侧细胞外神经递质较对照组均明显减少(P＜0.01);丘脑底核细胞外神经递质较对照组均明显增加(P＜0.05);苍白球外侧细胞外神经递质含量较对照组均无明显差异(P＞0.05).结论 3-NP可引起尾壳核神经递质变化,并通过直接和间接通路引起苍白球内侧及丘脑底核神经递质变化,从而诱发肌张力障碍.