IONIC CURRENTS AND SPIKING IN CEREBELLAR NUCLEAR NEURONS

小脑参与运动控制，其功能的破坏可导致各种运动障碍。小脑皮层的浦肯野神经元整合来自大脑多个区域的信号，在小脑核的神经元上形成抑制性突触，这些突触广泛地投射。尽管这种突触在小脑功能中的重要性，但小脑核神经元的电特性在很大程度上是未知的。这些神经元发射自发动作电位，即使在高自发抑制率的浦肯野神经元。这种活动的持续一定程度上是由于小脑核神经元固有的离子通道的特性。此外，浦肯野细胞中的快速信号传导可能导致神经递质耗竭，降低突触后抑制水平。该实验将确定小脑核神经元自发放电的离子电流，并确定浦肯野细胞抑制性突触输入的模式，这种模式成功地调节了小脑核神经元的放电。理解突触电流和内在电流之间的这种相互作用对于理解神经密码的基本要素至关重要，特别是，突触抑制是否一定会使突触后细胞沉默，或者它是否有时会使或增强放电。小脑核神经元将被酶从幼鼠中分离出来，并用于高质量的电压钳记录电流，这些电流是用通道特异性阻滞剂从药理学上分离出来的。电流将由动作电位波形组成的电压钳指令引起，从而可以直接测量导致放电的电流。在视觉控制下的小脑切片将被用来记录小脑核神经元对浦肯野神经元引起的高频和低频放电的反应。这种对特定神经元类别电流的实验测量对于开发精确的神经活动计算机模型，以及对小脑功能和功能障碍的系统级研究的细胞解释至关重要。

The cerebellum is involved in motor control, and disruption of its function can lead to a variety of movement disorders. Purkinje neurons of the cerebellar cortex, which integrate signals from many brain regions, form inhibitory synapses onto neurons of the cerebellar nuclei, which project widely. Despite the importance of this synapse in cerebellar function, the electrical properties of cerebellar nuclear neurons are largely unknown. These neurons fire spontaneous action potentials, even during high rates of spontaneous inhibition from Purkinje neurons. This persistence of activity must partly result from the properties of ion channels intrinsic to cerebellar nuclear neurons. Additionally, rapid signaling in Purkinje cells may lead to a depletion of neurotransmitter, reducing the level of postsynaptic inhibition. The proposed experiments will identify ionic currents underlying spontaneous firing in cerebellar nuclear neurons, as well as determine the patterns of inhibitory synaptic input from Purkinje cells that successfully modulate firing in cerebellar nuclear neurons. Understanding this interaction between synaptic and intrinsic currents is central to understanding a basic element of the neural code, specifically, whether synaptic inhibition necessarily silences a postsynaptic cell or whether it sometimes enables or enhances firing. Cerebellar nuclear neurons will by enzymatically isolated from young mice and used for high-quality voltage-clamp recordings of currents that are pharmacologically isolated with channel-specific blockers. Currents will be evoked by voltage-clamp commands consisting of action potential waveforms, allowing direct measurements of the currents contributing to firing. Cerebellar slices, under visual control, will be used to make recordings of responses of cerebellar nuclear neurons to high- and low- frequency firing evoked in Purkinje neurons. Such experimental measures of the currents in specific neuronal classes is essential to the development of accurate computer models of neural activity, as well as to cellular interpretations of systems-level studies of cerebellar function and dysfunction.