【作者】 薛雁；

【导师】 陈蕾；

【作者基本信息】 青岛大学 ， 神经生物学， 2010， 博士

【摘要】 苍白球(globus pallidus, GP)是基底神经节间接环路的重要核团,在机体运动功能调节中发挥重要作用。形态学研究证实苍白球接受来自纹状体的Y-氨基丁酸(Gamma-aminobutyric acid, GABA)和神经降压素(neurotensin, NT)能纤维支配,并表达相应受体。GABA是脑内最主要的抑制性递质。在帕金森病状态下苍白球GABAA受体表达降低,然而GABA含量明显增强。苍白球微量注射GABAA受体阻断剂bicuculline可以缓解帕金森病运动减少等症状。神经降压素是由13个氨基酸组成的肽类物质。在中枢神经系统,神经降压素作为神经递质或神经调质发挥重要作用,并且与中枢神经系统疾病密切相关。在6-羟基多巴胺(6-hydroxydopamine,6-OHDA)损毁的大鼠,全身给予一种可以穿过血脑屏障的神经降压素类似物,可以产生抗帕金森病效应。目的：探讨正常及帕金森病状态下苍白球内源性GABA和神经降压素的效应。方法：细胞外电生理记录,行为学,免疫组织化学等实验方法。结果：1.正常大鼠苍白球微量注射GABAA受体阻断剂gabazine可以使苍白球神经元放电频率由15.9±1.8 Hz升高到19.4±2.1 Hz,平均增加28.3±3.3%,与生理盐水组相比明显增强,差别有统计学意义(P<0.001)。2.在6-OHDA帕金森病模型大鼠损毁侧,gabazine对苍白球神经元的兴奋效应(46.0%)比未损毁侧(21.5%)和正常大鼠(28.3%)明显增强,差别有统计学意义(P<0.05)。3.在正常和帕金森病模型大鼠,gabazine引起的兴奋效应与苍白球神经元基础放电频率呈负相关性。4. GABAB受体阻断剂CGP55845仅能使正常和帕金森病模型大鼠苍白球神经元产生微弱的兴奋效应,与生理盐水组相比差别没有统计学意义(P>0.05)。5.在正常大鼠,单侧苍白球微量注射gabazine产生明显的对侧旋转行为(27.0±3.5圈/60min, n=8),与生理盐水对照组(2.3±0.8圈/60min, n=6)相比明显增加,差别有统计学意义(P<0.001)。在6-OHDA帕金森病模型大鼠损毁侧苍白球,微量注射gabazine可以增加由阿朴吗啡诱导的旋转圈数(25.5%),与生理盐水对照组(2.5%)相比明显增加,差别有统计学意义(P<0.01)。6.免疫组化染色显示在6-OHDA帕金森病模型大鼠损毁侧,苍白球GABAA受体al亚单位表达明显降低(P<0.01)。7.神经降压素可以兴奋正常和帕金森病模型大鼠苍白球神经元,使其放电频率增加(P<0.001)。神经降压素在帕金森病模型大鼠未损毁侧苍白球引起的兴奋效应(95.9%)比损毁侧(37.3%)和正常大鼠(48.3%)明显增强,差别有统计学意义(P<0.05)。8.双侧苍白球微量注射神经降压素可以缓解氟哌啶醇所致的僵直症状(P<0.05)。这种效应可以被选择性神经降压素1型受体拮抗剂SR48692阻断。9.在氟哌啶醇条件下,神经降压素可以兴奋苍白球神经元,放电频率由11.3±1.6Hz升高到14.8±1.9 Hz,平均增加34.9±3.2%(P<0.001)。这种效应可以被SR48692所阻断。10.正常大鼠侧脑室微量注射神经降压素可明显提高纹状体内多巴胺(dopamine,DA)含量(P<0.01)。6-OHDA帕金森病模型大鼠损毁侧纹状体DA含量与未损毁侧和正常大鼠相比明显降低(P<0.001)。损毁侧纹状体DA更新率(DOPAC+HVA)/DA、DOPAC/DA、HVA/DA均明显高于未损毁侧和正常大鼠(P<0.001)。帕金森病模型大鼠侧脑室微量注射神经降压素可明显提高损毁侧和未损毁侧纹状体DA含量(P<0.05)。结论：Gabazine可以兴奋苍白球神经元,增加由阿朴吗啡诱导的帕金森病模型大鼠的旋转圈数,提示阻断苍白球内源性GABAA受体可以拮抗帕金森病状态下过度的纹状体-苍白球GABA能纤维支配。神经降压素通过激活神经降压素1型受体兴奋苍白球神经元,而且神经降压素还可以增加纹状体多巴胺含量。上述实验结果为苍白球GABA和神经降压素等递质系统抗帕金森病的机制提供了一定的理论和实验依据。更多还原

【Abstract】 The globus pallidus is an important structure in the indirect pathway of the basal ganglia circuit. By innervating all the other basal ganglia nuclei, the globus pallidus plays a critical role in movement regulation. Morphological studies have revealed a high level of GABA and GABAA receptors in the globus pallidus. The expression of GABAA receptors in the globus pallidus was decreased under parkinsonian state, while the GABA content was increased. Early studies have revealed that microinjection of GABAA receptor antagonist, bicuculline, into the globus pallidus had marked antiparkinsonian effects. Neurotensin is a tridecapeptide which plays an important role in the central nervous system by acting either as a neurotransmitter or a neuromodulator. Systemic administration of a neurotensin analog that can cross the blood-brain barrier produced antiparkinsonian effects in 6-hydroxydopamine (6-OHDA)-lesioned rats. Morphological studies have indicated that the globus pallidus receives neurotensinergic innervation from the striatum, and both neurotensin type-1 and type-2 receptors are present in the globus pallidus. Object:To investigate the effects of endogenous GABA and neurotensin in the globus pallidus of normal and parkinsonian rats. Methods:in vivo extracellular recording, behavioral tests and immunohistochemistry were performed in the present studies. Results:1. In normal rats, micro-pressure ejection of GABAA receptor antagonist, gabazine, increased the spontaneous firing rate of pallidal neurons from 15.9±1.8 Hz to 19.4±2.1 Hz. The average increase was 28.3±3.3%, which was significantly different (P<0.001) from that of vehicle (normal saline) injection.2. In 6-OHDA parkinsonian rats, gabazine increased the firing rate by 46.0% on the lesioned side, which was significantly greater than that on the unlesioned side (21.5%, P<0.05), as well as that in normal rats (28.3%, P<0.05).3. A negative correlation between gabazine-induced excitation and the basal firing rate was observed in globus pallidus neurons of both normal and 6-OHDA parkinsonian rats.4. Micro-pressure ejection of GABAB receptor antagonist, CGP55845, only produced a weak increase in the firing rate of globus pallidus neurons in normal and parkinsonian rats, which was not significantly different from that of control group (P>0.05).5. In the behaving rats, unilateral microinjection of gabazine evoked consistent contralateral rotation in normal rats (P<0.001), and significantly potentiated apomorphine-induced contralateral rotations in 6-OHDA parkinsonian rats (P<0.01).6. The expression of GABAA receptor al subunit was decreased in the globus pallidus on the lesioned side of 6-OHDA lesioned rats (P<0.01).7. Micro-pressure ejection of neurotensin into the globus pallidus increased the spontaneous firing rate of pallidal neurons in normal and 6-OHDA parkinsonian rats (P<0.001). The neurotensin-induced increase in firing rate of globus pallidus on unlesioned side (95.9%) was stronger than that on lesioned side (37.3%, P<0.05) and normal rats (48.3%, P<0.05).8. Bilateral microinjection of neurotensin into the globus pallidus significantly attenuated haloperidol-induced catalepsy (P<0.05). This anticataleptic effect was completely counteracted by SR48692.9. Microinjection of neurotensin excited pallidal neurons from 11.3±1.6 Hz to 14.8±1.9 Hz in the presence of systemic haloperidol administration. The average increase was 34.9±3.2% (P<0.001). SR48692 blocked the excitatory effect induced by neurotensin.10. In normal rats, intracerebroventricular microinjection of neurotensin significantly elevated the concentration of dopamine in the striatum (P<0.01). In 6-OHDA parkinsonian rats, the striatal dopamine level on the lesioned side was significantly decreased compared with that on the unlesioned side and normal rats (P<0.001), while the turnover ratio, (DOPAC+HVA)/DA, DOPAC/DA and HVA/DA, were significantly increased (P<0.001). Furthermore, microinjection of neurotensin significantly elevated the striatal dopamine level on both sides of 6-OHDA parkinsonian rats (P<0.05).Conclusion:The present study indicated that gabazine increased the spontaneous firing rate of globus pallidus neurons and potentiated apomorphine-induced contralateral rotation in 6-OHDA lesioned rats. Therefore, blockade of GABAA receptors in globus pallidus could counteract the excessive striato-pallidal activity under parkinsonian state. Neurotensin increased the activity of globus pallidus neurons and also increased the dopamine level in striatum on both normal and 6-OHDA parkinsonian rats. The present electrophysiological, behavioral and immunohistochemical studies may provide a rational for further investigations into the potential of pallidal GABAergic and neurotensinergic neurotransmission in the treatment of Parkinson’s disease.更多还原