【作者】 王天琳；

【导师】 吴春福；

【作者基本信息】 沈阳药科大学 ， 药理学， 2009， 硕士

【摘要】 成瘾性药物滥用是威胁人类生存的重大社会问题。乙醇、甲基苯丙胺、吗啡及尼古丁是广泛滥用的成瘾性药物,对其作用机制的研究有助于更好的预防和治疗相关成瘾性疾病。近年来,尿嘧啶作为中枢神经系统中最重要的神经调质之一,其功能的多元化越发引起人们的关注,但其与成瘾性药物的关系还鲜有报道。纹状体作为大脑的高级中枢在药物依赖及成瘾过程中发挥重要作用,但相关机制研究仍然十分有限。本文从神经化学水平研究了成瘾性药物对纹状体尿嘧啶含量的影响,并对其机制进行了初步探讨。本文首先采用了高效液相色谱结合脑内微透析技术,考察了乙醇、甲基苯丙胺、吗啡和尼古丁四种成瘾性药物急性应用对小鼠纹状体细胞外尿嘧啶含量的影响。结果表明,与空白组相比,四种成瘾性药物急性应用均能够剂量依赖性地降低小鼠纹状体细胞外尿嘧啶的含量。为了鉴别尿嘧啶的变化是否与成瘾性药物引起的兴奋或抑制作用有关,本研究分别考察了透析灌流给予海人藻酸(KA)和高浓度钾离子引起的纹状体细胞去极化,以及腹腔注射镇静催眠药物地西泮和水合氯醛对小鼠纹状体细胞外尿嘧啶含量的影响。结果显示,KA和高浓度钾离子使尿嘧啶水平增高,地西泮引起尿嘧啶水平降低,水合氯醛对其无明显影响。提示上述成瘾性药物引起的纹状体细胞外尿嘧啶含量变化与其对中枢的兴奋或抑制作用无关。接下来本文考察了μ受体拮抗剂纳洛酮和/或NMDA受体拮抗剂MK-801对吗啡、甲基苯丙胺降低小鼠纹状体尿嘧啶含量作用的影响。结果表明,纳洛酮和MK-801可分别拮抗吗啡引起的尿嘧啶水平降低；MK-801能够阻断甲基苯丙胺的这种作用。提示吗啡对尿嘧啶的下调作用与μ受体和NMDA受体有关；甲基苯丙胺引起尿嘧啶含量下降与NMDA受体有关。随后本论文进一步考察以上所有药物对小鼠纹状体总RNA含量的影响,结果提示,乙醇、甲基苯丙胺、吗啡和尼古丁对小鼠纹状体细胞外尿嘧啶释放的影响与细胞内总RNA的含量变化存在相关性。综上所述,成瘾性药物可调节纹状体细胞外尿嘧啶的释放以及细胞内总RNA的表达,且这种调节可能是通过其相关受体实现的。提示尿嘧啶与成瘾性药物的中枢作用相关,且尿嘧啶有成为探索成瘾机制新指标的潜质,而其与成瘾性药物作用的相关机制还需进一步深入研究。更多还原

【Abstract】 Drug abuse, including ethanol, methamphetamine (MAP), morphine and nicotine, is an important social problem as well as public health problem throughout the world. Although considerable progress has been made to explain the mechanism of addiction, it is still unclear. Uracil has been known not only to be a fundamental intermediate in the synthesis of the pyrimidine nucleotides, but also an important neuromodulator in the central nervous system(CNS). The present study was performed to investigate the effects of drugs of abuse on extracellular uracil level in the striatum, an important brain region implicated in addiction, in mice, as well as the preliminary mechanism.In vivo microdialysis coupled to high performance liquid chromatography (HPLC) was employed to detect the extracellular contents of uracil in the striatum. And total RNA level was determined by spectrophotometry.It was found that acute adiminstration of ethanol, MAP, morphine or nicotine could decrease uracil level in a dose-dependent manner in mice striatum. Depolarization, achieved by administering kainic acid (KA) or high concentration of potassium in striatum, increased extracellular uracil contents. And in the case of intraperitoneal administration of sedative-hypnotic drugs, diazepam and chloral hydrate, the effects were different. Diazepam decreased uracil level, whereas there was no significant effect of chloral hydrate. It is indicated that the induction of decreased uracil level by drugs of abuse was not mediated by their excitory or inhibitory effect on CNS.Meanwhile, naloxone and MK-801, antagonists of mu-opioid receptor and NMDA receptor respectively, inhibited uracil decrease induced by morphine administration. Similarly, MK-801 could block the effect of MAP on striatal uracil level. It is suggested that mu-opioid receptor and/or NMDA receptor were involved in the mechanism of morphine or MAP induced decrease of striatal uracil level. In addition, the effects of all the drugs of abuse on total striatal RNA contents were found to be relevant with their effects on extracellurlar uracil level in mice.In conclusion, the present study firstly found the changes of striatal uracil level induced by drugs of abuse, which may contribute to explain the effects of these drugs in the CNS.更多还原