大麻素 CB 受体介导的小鼠腹侧被盖区多巴胺能神经元兴奋性降低的机制。
Mechanisms of cannabinoid CB receptor-mediated reduction of dopamine neuronal excitability in mouse ventral tegmental area.
机构信息
Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders, Shandong Provincial Collaborative Innovation Center for Neurodegenerative Disorders and State Key Disciplines: Physiology, Medical College of Qingdao University, Qingdao 266071, China; Department of Neurobiology, St. Joseph's Hospital and Medical Center, Barrow Neurological Institute, Phoenix, AZ 85013, USA.
Department of Pharmacology, Shantou University Medical College, Shantou, Guangdong 210854, China; Department of Neurobiology, St. Joseph's Hospital and Medical Center, Barrow Neurological Institute, Phoenix, AZ 85013, USA.
出版信息
EBioMedicine. 2019 Apr;42:225-237. doi: 10.1016/j.ebiom.2019.03.040. Epub 2019 Apr 3.
BACKGROUND
We have recently reported that activation of cannabinoid type 2 receptors (CBRs) reduces dopamine (DA) neuron excitability in mouse ventral tegmental area (VTA). Here, we elucidate the underlying mechanisms.
METHODS
Patch-clamp recordings were performed in mouse VTA slices and dissociated single VTA DA neurons.
FINDINGS
Using cell-attached recording in VTA slices, bath-application of CBR agonists (JWH133 or five other CBR agonists) significantly reduced VTA DA neuron action potential (AP) firing rate. Under the patch-clamp whole-cell recording model, JWH133 (10 μM) mildly reduced the frequency of miniature excitatory postsynaptic currents (mEPSCs) but not miniature inhibitory postsynaptic currents (mIPSCs). JWH133 also did not alter evoked EPSCs or IPSCs. In freshly dissociated VTA DA neurons, JWH133 reduced AP firing rate, delayed AP initiation and enhanced AP after-hyperpolarization. In voltage-clamp recordings, JWH133 (1 μM) enhanced M-type K currents and this effect was absent in CB mice and abolished by co-administration of a selective CBR antagonist (10 μM, AM630). CBR-mediated inhibition in VTA DA neuron firing can be mimicked by M-current opener (10 μM retigabine) and blocked by M-current blocker (30 μM XE991). In addition, enhancement of neuronal cAMP by forskolin (10 μM) reduced M-current and increased DA neuron firing rate. Finally, pharmacological block of synaptic transmission by NBQX (10 μM), D-APV (50 μM) and picrotoxin (100 μM) in VTA slices failed to prevent CBR-mediated inhibition, while intracellular infusion of guanosine 5'-O-2-thiodiphosphate (600 μM, GDP-β-S) through recording electrode to block postsynaptic G-protein function prevented JWH133-induced reduction in AP firing.
INTERPRETATION
Our results suggest that CBRs modulate VTA DA neuron excitability mainly through an intrinsic mechanism, including a CBR-mediated reduction of intracellular cAMP, and in turn enhancement of M-type K currents. FUND: This research was supported by the Barrow Neuroscience Foundation, the BNI-BMS Seed Fund, and CNSF (81771437).
背景
我们最近报道，大麻素受体 2 型（CBR2）的激活可降低小鼠腹侧被盖区（VTA）中多巴胺（DA）神经元的兴奋性。在这里，我们阐明了潜在的机制。
方法
在小鼠 VTA 切片和分离的单个 VTA DA 神经元中进行膜片钳记录。
发现
在 VTA 切片的细胞附着记录中，CBR 激动剂（JWH133 或其他 5 种 CBR 激动剂）的浴应用显著降低了 VTA DA 神经元动作电位（AP）的发射率。在膜片钳全细胞记录模型下，JWH133（10 μM）轻度降低了微小兴奋性突触后电流（mEPSC）的频率，但不改变微小抑制性突触后电流（mIPSC）。JWH133 也不改变诱发的 EPSC 或 IPSC。在新分离的 VTA DA 神经元中，JWH133 降低了 AP 发射率，延迟了 AP 的起始并增强了 AP 后超极化。在电压钳记录中，JWH133（1 μM）增强了 M 型 K 电流，而在 CB 小鼠中这种作用不存在，并且被选择性 CBR 拮抗剂（10 μM，AM630）共同给药所阻断。VTA DA 神经元放电中的 CBR 介导的抑制可以被 M 电流激动剂（10 μM 瑞替加滨）模拟，并被 M 电流阻断剂（30 μM XE991）阻断。此外，通过佛波醇（10 μM）增强神经元中的 cAMP 会降低 M 电流并增加 DA 神经元的发射率。最后，在 VTA 切片中，通过 NBQX（10 μM）、D-APV（50 μM）和 Picrotoxin（100 μM）阻断突触传递的药理学阻断未能阻止 CBR 介导的抑制，而通过记录电极向细胞内输注鸟苷 5'-O-2-硫代二磷酸（600 μM，GDP-β-S）以阻断突触后 G 蛋白功能则可防止 JWH133 诱导的 AP 发射减少。
解释
我们的结果表明，CBR 通过一种内在机制调节 VTA DA 神经元的兴奋性，包括 CBR 介导的细胞内 cAMP 减少，进而增强 M 型 K 电流。
资金
这项研究得到了巴罗神经科学基金会、BNI-BMS 种子基金和中国国家自然科学基金（81771437）的支持。
Zotero 插件