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吗啡戒断重塑大鼠伏隔核毒蕈碱受体功能
其他题名Morphine withdrawal results in altered muscarinic receptor function in rat nucleus accumbens
江潇
学位类型博士
导师隋南
2013-11
学位授予单位中国科学院研究生院
学位授予地点北京
学位专业心理学
关键词伏隔核中等多棘神经元 内在兴奋性 兴奋性突触传递 毒蕈碱受体 吗啡戒断
摘要伏隔核(nucleus accumbens,NAc)是各种成瘾药物产生奖赏和复吸的关键核团。阿片类药物引起的NAc 适应性变化导致其对药物及相关刺激发生敏感化,进而促使了强迫性觅药和渴求的发生。停药后经过一段时间的潜伏(incubation)敏感化现象更强,促使了成瘾的长期存在。
中等多棘神经元(medium spiny neuron,MSN)是NAc 的传出神经元,占神经元总数的90-95%。决定MSN 电信号的输出主要有两个因素:兴奋性突触传递和膜内在兴奋性。反复阿片类药物作用后,两者都发生了适应性变化,在药物渴求和觅药行为中发挥重要作用。在不同的戒断时间点,两者变化的方向和/或强度不是单一的,随着戒断时间的延长呈现动态的变化,为敏感化的incubation现象提供了细胞机制,但可能涉及的机制不清楚。乙酰胆碱(acetylcholine,ACh)系统对NAc 介导的阿片成瘾有着重要的调节作用。NAc 内ACh 通过作用于毒蕈碱受体(muscarinic acetylcholine receptor,mAChR)对MSN 的兴奋性突触传递和内在兴奋性有着重要的调节作用。为探讨NAc 内mAChR 在吗啡成瘾中的作用机制及其与戒断时间的关系,本研究主要采用全细胞脑片膜片钳技术,系统观
察了吗啡反复使用后,短期戒断(停药5-6 天)和长期戒断(停药15-18 天)对mAChR 调节大鼠NAc 核部MSN 兴奋性突触传递和内在兴奋性作用的影响及可能的机制。结果主要观察到:
(1)在正常大鼠NAc 核部MSN,mAChR 激动剂浓度依赖性降低诱发兴奋性突触后电位(evoked excitatory postsynaptic potentials,eEPSP)幅度、增加eEPSP的双脉冲易化值(paired-pulse facilitation ratio,PPR)、降低自发兴奋性突触后电流(spontaneous excitatory postsynaptic current,sEPSC)幅度和频率。表明,突触前mAChR 通过减少谷氨酸释放导致兴奋性突触传递减弱;mAChR 激动剂浓度依赖性诱发MSN 内向电流,表明突触后、外mAChR 可增强MSN 内在兴奋性;MSN 上μ 阿片受体(mu opioid receptor,MOP-R)激活降低了mAChR 内向电流,表明MSN 上MOP-R 激活可减弱突触后、外mAChR 兴奋MSN 的能力。
(2)反复吗啡暴露后短期戒断时,mAChR 激动剂对sEPSC 幅度和频率的抑制作用都无变化;mAChR 激动剂诱发的内向电流幅度增加;MSN 上MOP-R激活对mAChR 内向电流抑制作用增强。表明短期戒断,突触前mAChR 功能无变化,对兴奋性突触传递抑制作用未变;突触后、外mAChR 功能增强,提高内在兴奋性的能力增强;MSN 上MOP-R 减弱突触后、外mAChR 功能的能力增强。
(3)吗啡长期戒断时,mAChR 激动剂对sEPSC 幅度的抑制作用无变化,对sEPSC 频率的抑制作用减弱;mAChR 激动剂诱发的内向电流幅度减弱;MSN上MOP-R 对mAChR 内向电流抑制作用无变化。表明长期戒断,突触前mAChR功能减弱,对兴奋性突触传递抑制作用降低;突触后、外mAChR 功能减弱,提高内在兴奋性的能力减弱;MSN 上MOP-R 减弱突触后、外mAChR 功能的能力未变。
以上结果提示,反复吗啡暴露后戒断可引起NAc 内mAChR 功能变化,导致MSN 兴奋性突触传递和膜内在兴奋性随戒断时间的延长而呈现动态的改变,同一个MSN上的MOP-R代偿性拮抗了mAChR功能变化,可能是NAc内mAChR参与吗啡觅药和渴求行为的神经机制之一,且在细胞层面上支持了incubation 现象。
其他摘要Nucleus accumbens (NAc) is a crucial brain region underlying reward and relapse by all kinds of addictive drugs. Adaptive changes in NAc induced by opiates result in the hyperreactivity of NAc to drugs and relevant stimulus, then prompt the compulsive drug seeking and craving. The hyperreactivity progressively increases over the incubation of withdrawal time, which can account for the persistent dependence.
Medium spiny neuron (MSN), which constitutes 90-95% in all neuronal populations of NAc, is the efferent neuron. Electrical output of MSN mainly depends on the integration of excitatory synaptic transmission and intrinsic excitability.
Adaptive changes of both by repeated opioids exposure are believed to play a central role in promoting drug craving and drug-seeking behaviors. The direction and level of their alterations are not single or consistent at different withdrawal time, they both show dynamic alterations as withdrawal time extending. This phenomenon may be a cellular mechanism underlying the incubation of sensitization, however, the involved mechanisms has not been thoroughly examined. Acetylcholine (ACh) plays an important role in modulating NAc-mediated opioid dependence. Muscarinic acetylcholine receptor (mAChR) in NAc plays a vital role in modulating excitatory synaptic transmission and intrinsic excitability of MSN. To explore the neural mechanisms of NAc mAChR underlying morphine dependence and the interaction of
these mechanisms and withdrawal time. The whole-cell patch-clamp recordings in MSN of NAc slices from rats were mainly performed, rats were pretreated by intermittent morphine or saline injection. Effects of mAChR activation on excitatory synaptic transmission and intrinsic excitability of MSN in NAc core and their possible mechanism at short-term withdrawal (5-6 days) and long-term withdrawal (15-18 days) time were observed. The main results are as follows:
(1) In NAc core MSN of naive rats, the mAChR agonist concentration-dependently decreased the amplitudes of evoked excitatory postsynaptic potentials (eEPSP), increased paired-pulse facilitation ratio (PPR) of eEPSP and decreased amplitudes and frequency of spontaneous excitatory postsynaptic current (sEPSC). These suggest presynaptic mAChR activation attenuate excitatory synaptic transmission by decreaing glutamate release. The mAChR agonist concentration-dependently induced membrane inward currents, which suggests postand extrasynaptic mAChR can potentiate intrinsic excitability of MSN. Mu opioid receptor (MOP-R) activation decreased mAChR-mediated inward currents in the same MSN, which suggests MOP-R activation can attenuate the excitatory ability of mAChR on MSN.
(2) During intermittent morphine exposure and short-term withdrawal time, effects of the mAChR agonist on both of sEPSC amplitude and frequency were unchanged, on both of membrane currents and the inhibitory role of MOP-R activation on mAChR-mediated inward currents were increased. These suggest the inhibitory role of presynaptic mAChR on excitatory synaptic transmission was unchanged; the intensive role of post- and extrasynaptic mAChR on intrinsic excitability was increased; the inhibitory role of MOP-R on post- and extrasynaptic
mAChR signaling was increased.
(3) At long-term withdrawal time, effects of the mAChR agonist on sEPSC amplitude, sEPSC frequency, membrane currents and the inhibitory role of MOP-R activation on mAChR-mediated inward currents were unchanged, decreased, decreased and unchanged, respectively. These suggest the inhibitory role of presynaptic mAChR on excitatory synaptic transmission was decreased; the intensive role of post- and extrasynaptic mAChR on intrinsic excitability was decreased; the inhibitory role of MOP-R on post- and extrasynaptic mAChR signaling was unchanged.
These results suggest intermittent morphine exposure and withdrawal could alter mAChR signaling in NAc, which played dynamic alterations as the withdrawal time extending. The co-existed MOP-R activation compensatorily antagonizes post- and extrasynaptic mAChR signaling. These may contribute to the role of NAc mAChR in morphine craving and seeking, and support the incubation of sensitization in a cellular manner.
学科领域医学心理学
语种中文
文献类型学位论文
条目标识符http://ir.psych.ac.cn/handle/311026/19601
专题健康与遗传心理学研究室
作者单位中国科学院心理研究所
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江潇. 吗啡戒断重塑大鼠伏隔核毒蕈碱受体功能[D]. 北京. 中国科学院研究生院,2013.
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