Synaptic regulation of single substantia nigra pars reticulata neurons

描述(申请人提供)：丘脑底核(STN)通过对黑质网状核(SNR)的兴奋影响在运动控制中发挥重要作用，SNR是基底节的主要输出结构。在帕金森氏病中，大脑皮质爆发性活动增加 丘脑黑质下部通路被认为与强直、运动迟缓和震颤等运动症状有关。我们实验室的初步数据显示，对STN的焦点电刺激引起最初的单突触EPSC，随后是一系列晚期EPSC，叠加在持续200-500ms的保持电流的缓慢内移上。到目前为止，结果支持这样的假设，即这种复杂的EPSC是通过激活STN内的经常性轴突侧支而产生的。因为STN刺激唤起了 当记录在电流钳下时，动作电位的爆发，复合EPSC可能代表了一种促进SNR神经元爆发放电的新机制。相反，刺激STN只在黑质致密部(SNC)多巴胺神经元中诱发单相EPSCs，这表明STN对SNR的输出可能不同于STN对SNC多巴胺神经元的输出。我们提出的研究的主要目标是描述复杂的EPSCs的神经生理学特征以及神经递质系统对它们的调节。实验将使用标准的全细胞膜片移液管记录技术来记录大鼠脑片中的神经元。复杂的EPSCs将通过对STN的局部电刺激在SNR神经元中被诱发，药物溶液将使用快速流动的微型敷贴器被输送到脑片的特定区域。计划中的实验将使用SNR和SNC的逆行刺激技术来表征STN内反复出现的多突触连接。其他实验将研究GABA和多巴胺受体配体调节复杂EPSCs的作用部位并表征受体药理学。与 在神经生理学实验中，脑片也将被用来在电子显微镜下记录STN神经元的经常性轴突侧支神经支配。由于丘脑黑质下部通路在调节SNR神经元放电模式中的重要性，这些研究结果可能对帕金森病的病理生理学和可能的治疗具有重要意义。与公共健康相关：许多研究表明，大脑通路中过度的爆发性活动来自 丘脑底核至黑质网状部有助于帕金森氏病的症状以及某些类型癫痫的传播。我们的研究表明，激活丘脑黑质下部通路会在大鼠脑片上记录到网状神经元的持久去极化和动作电位爆发。通过表征突触连接和调制递质系统是如何调节这一途径的，我们的研究可能会为改进这些人类疾病的治疗提供有用的信息。

DESCRIPTION (provided by applicant): The subthalamic nucleus (STN) plays an important role in movement control by exerting its excitatory influence on the substantia nigra pars reticulata (SNR), a major output structure of the basal ganglia. In Parkinson's disease, increased bursting activity in the subthalamonigral pathway is thought to contribute to motor symptoms such as rigidity, bradykinesia and tremor. Preliminary data from our lab show that focal electrical stimulation of the STN evokes an initial monosynaptic EPSC followed by a series of late EPSCs superimposed on a slow inward shift in holding current that lasts 200 - 500 ms. Results thus far support the hypothesis that this complex EPSC is generated by activation of recurrent axon collaterals within the STN. Because STN stimulation evokes a burst of action potentials when recording under current-clamp, the complex EPSC may represent a novel mechanism for promoting burst firing in SNR neurons. In contrast, STN stimulation only evokes monophasic EPSCs in substantia nigra pars compacta (SNC) dopamine neurons, which suggests that the STN output to SNR may differ from the STN output to SNC dopamine neurons. The major goals of our proposed studies are to characterize the neurophysiology of complex EPSCs and their regulation by neurotransmitter systems. Experiments will use standard whole-cell patch pipette recording techniques to record from neurons in the rat brain slice. Complex EPSCs will be evoked in SNR neurons by focal electrical stimulation of the STN, and drug solutions will be delivered to specific regions of the brain slice using a fast-flow microapplicator. Planned experiments will use antidromic stimulation techniques of the SNR and SNC to characterize recurrent, polysynaptic connections within the STN. Other experiments will investigate sites of action and characterize receptor pharmacology for the regulation of complex EPSCs by GABA and dopamine receptor ligands. In conjunction with neurophysiological experiments, brain slices will also be used to document recurrent axonal collateral innervation of STN neurons using electron microscopy. Due to the importance of the subthalamonigral pathway in regulating firing pattern of SNR neurons, results of these studies may have important implications for the pathophysiology and possible treatment of Parkinson's disease. PUBLIC HEALTH RELEVANCE: Many studies suggest that excessive bursting activity in the brain pathway from subthalamic nucleus to substantia nigra pars reticulata contributes to symptoms of Parkinson's disease as well as the propagation of some types of seizures. Our studies show that activation of the subthalamonigral pathway causes long-lasting depolarization and bursts of action potentials in reticulata neurons recorded in the rat brain slice. By characterizing how synaptic connections and modulatory transmitter systems regulate this pathway, our studies may provide useful information to improve the therapy of these human disorders.