【作者】 亓佳；

【导师】 吴春福；

【作者基本信息】 沈阳药科大学 ， 药理学， 2008， 博士

【摘要】 以甲基苯丙胺为代表的精神兴奋剂的滥用已经成为一个严重的社会问题,其精神依赖性是其泛滥的重要原因。催产素是一种垂体神经肽,具有多方面的生理功能。近年来的研究认为它可以作为一种神经调质参与调节学习记忆,应激以及多种药物成瘾的中枢神经系统作用。目前,催产素对甲基苯丙胺精神依赖性方面的作用及其机制研究尚无文献报道。本论文从行为学,神经化学和分子生物学三个水平研究了催产素在甲基苯丙胺精神依赖性中的作用并对其相关机制进行了初步探讨。本文首先采用了自主活动测定,行为敏化和条件性位置偏爱模型结合脑室给药技术,考察了催产素在甲基苯丙胺引起的精神依赖中的作用。在行为敏化实验中,甲基苯丙胺可以使小鼠自主活动增加并形成稳定的行为敏化,停止给药后再次给予甲基苯丙胺敏化可得以表达。脑室注射催产素可以剂量依赖性的抑制甲基苯丙胺引起的小鼠自主活动增加,抑制行为敏化的转化和表达,而对形成没有显著性影响。在甲基苯丙胺诱导的条件性位置偏爱实验中,催产素可以显著抑制其形成,加速其消退并抑制由于束缚应激引起的重现,但对于条件性位置偏爱的表达和药物激发引起的重现没有明显作用。催产素对上述行为学效应的影响均可被其受体拮抗剂阿托西班所阻断,提示催产素的作用是通过其位于中枢神经系统的受体来发挥的。论文进一步采用高效液相的方法检测脑内与成瘾密切相关的单胺神经递质系统(多巴胺能,5-羟色胺能)变化。实验结果表明,催产素可以通过影响纹状体和伏隔核的多巴胺代谢调节甲基苯丙胺引起的小鼠自主活动增高。纹状体和伏隔核内的多巴胺通路参与了甲基苯丙胺引起的行为敏化,并且,催产素可以调节该通路中多巴胺的代谢抑制甲基苯丙胺行为敏化的转化和表达,而前皮层和海马中多巴胺,5-羟色胺及其代谢产物的含量变化不是引起小鼠行为改变的主要原因。以上结果进一步阐明了奖赏通路在甲基苯丙胺精神依赖性方面的重要作用。谷氨酸作为兴奋性氨基酸类神经递质在脑内广泛存在。除了中脑边缘多巴胺能系统,谷氨酸能系统在药物成瘾中也起到重要作用,此系统主要起源于前额叶皮层。因此本文采用在体脑内微透析结合高效液相技术研究了催产素对甲基苯丙胺引起小鼠前额叶皮层内细胞外谷氨酸含量变化的影响,同时实验还检测了两种抑制性氨基酸牛磺酸和γ-氨基丁酸的含量。研究发现催产素可以抑制单次注射甲基苯丙胺以及束缚应激引起的成瘾消退小鼠内侧前额叶皮层细胞外谷氨酸含量升高,但对于药物激发引起的谷氨酸升高没有显著抑制作用。此外,单独脑室注射催产素可以引起前额叶皮层内牛磺酸和γ-氨基丁酸含量升高,而谷氨酸含量变化不大,结果提示急性给予催产素后前额叶皮层可能呈现一种抑制状态。近几年来关于药物成瘾与学习记忆相关性的研究日渐深入,尤其是皮层和海马等与学习记忆相关的脑区中谷氨酸的受体和转运体在成瘾中的作用也成为研究热点。本文采用免疫印迹(Western Blotting)实验方法检测了催产素对甲基苯丙胺引起小鼠前额叶皮层和海马内谷氨酸受体NMDAR1亚型和转运体GLT1亚型表达含量变化的影响。研究表明急性给予甲基苯丙胺及其激发复吸时均可以显著增加前额叶皮层内NMDAR1蛋白的含量,而戒断时前额叶皮层内NMDAR1含量显著下降。催产素可以显著拮抗甲基苯丙胺引起的NMDAR1水平的变化。另一方面,急、慢性给予甲基苯丙胺及其激发复吸时均可以显著增加海马内GLT1蛋白的含量,催产素可以进一步增加急性和慢性给予甲基苯丙胺时海马内GLT1的水平。催产素自身对前额叶皮层和海马部位NMDAR1和GLT1含量没有显著性影响。结果提示,催产素可以通过调节谷氨酸受体和转运体两方面的作用,削弱甲基苯丙胺对谷氨酸含量变化的影响,以直接或间接达到调节兴奋性氨基酸在成瘾中的作用。综上所述,脑室注射催产素可以通过调解中枢奖赏系统中多巴胺的代谢,氨基酸系统中细胞外谷氨酸,牛磺酸和γ-氨基丁酸水平,以及前额叶皮层和海马中谷氨酸受体和转运体的表达来调节甲基苯丙胺精神依赖引起的行为学变化,并且催产素是通过其位于中枢的受体来产生作用的。更多还原

【Abstract】 Methamphetamine (MAP), a psychostimulant, is abused in all of the world, which remains a major social problem. MAP-induced psychological dependence is the main reason of its abuse. Accumulated data have shown the neuroactive properties of oxytocin (OT), a neurohypophyseal neuropeptide, and its capable of reducing the abuse potential of drugs. The present study investigated the effects of OT on MAP-induced behavioral changes in mice and its possible mechanisms of action.First of all, locomotor activity (LA), behavioral sensitization (BS) and conditioned place preference (CPP) models were used to investigate the effects of OT on the behavioral changes induced by MAP in mice. The results showed that intracerebroventricular administration of OT had no effect on locomotor activity in naive mice, but inhibited, in a dose-dependent manner, the hyperactivity induced by acute administration of MAP. OT inhibited the acquisition, facilitated the extinction of MAP-induced CPP and abolished the reinstatement of CPP induced by restraint stress significantly. Moreover, OT blocked the transfer and expression of BS. However, OT had no effect on the development of BS, the expression and the reinstatement of CPP induced by MAP challenge. These effects of OT could be attenuated by atosiban (Ato), a selective OT receptor antagonist, which suggests that OT inhibits drug-seeking behaviors induced by MAP via its receptor.As well known, the mesocorticolimbic dopaminergic system plays a key role in MAP dependence. The high-performance liquid chromatography (HPLC) with electronic detection system was employed in the study to determine the dopamine (DA) and serotonin (5-HT) turnover ratios in prefrontal cortex (PFC), hippocampus, striatum and nucleus accumbens (NAc) of mice. The results showed that OT significantly inhibited the DA turnover ratios in striatum and NAc in acute or chronic MAP-treated mice. These results suggest that OT inhibits the MAP-induced alteration of DA turnover in mesolimbic region of mice.In addition to the mesocorticolimbic dopaminergic system, glutamate (Glu)-mediated synaptic transmission also involves in the psychostimulant abuse. PCF is the origin of the glutamatergic efferents. In the present study, the extracellular Glu levels in the medial prefrontal cortex (mPFC) were determined by using microdialysis coupled to a HPLC with fluorescence detection system. The results indicated OT markedly inhibited the increase of extracellular Glu levels in mPFC of mice induced by acute administration of MAP and restraint stress in CPP mice, but not that induced by MAP priming. Furthermore, OT increased the taurine (Tau) and gamma-aminobutyric acid (GABA) levels in mPFC of naive mice, which suggested that mPFC was in the inhibitory status after OT administration.Previous studies have suggested that glutamatergic receptors (NMDAR1 subunit) and transporters (GLT1 subunit) are mainly involved in the addiction of drug abused. The present studies by using Western blotting method detected the expression of NMDAR1 and GLT1 in PFC and hippocampus after acute and chronic MAP administration. The results showed that OT significantly inhibited the increased NMDAR1 levels in PFC induced by acute MAP and MAP-challenging relapse and markedly attenuated the decreased NMDAR1 levels in PFC induced by MAP withdrawal. Moreover, OT increased the elevated GLT1 levels in hippocampus after acute and chronic MAP administration. No significant differences of NMDAR1 and GLT1 expression in hippocampus and PFC of mice were observed after treated with OT alone. The results indicate that OT attenuates the changes of glutamatergic neurotransmission induced by MAP partially via NMDAR1 and GLT1.In conclusion, although the mechanisms underlying the OT effect are not clear enough, it appears that the ability of OT to modulate MAP-induced psychological dependent behavior is closely related to the effects of the neuropeptide on dopaminergic neurotransmission in the mesolimbic regions and the glutamatergic neurotransmission of the brain. In addition, the present results implicated that OT might be a potential candidate for the prevention and treatment of the neurological disorders induced by amphetamine-like compounds.更多还原