IONIC CURRENTS AND SPIKING IN CEREBELLAR NUCLEAR NEURONS

小脑参与运动控制，其功能的中断可导致各种运动障碍。小脑皮质的浦肯野神经元整合来自许多大脑区域的信号，形成抑制性突触到小脑核的神经元上，这些神经元广泛投射。尽管这种突触在小脑功能中的重要性，小脑核神经元的电特性在很大程度上是未知的。这些神经元激发自发动作电位，即使在浦肯野神经元自发抑制的高速率期间。这种活性的持续性一定部分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的耗尽，降低突触后抑制的水平。拟议的实验将确定离子电流的自发放电小脑核神经元，以及确定模式的抑制性突触输入浦肯野细胞，成功地调制放电小脑核神经元。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，具体来说，突触抑制是否必然会使突触后细胞沉默，或者它是否有时会使放电发生或增强放电。小脑核神经元将通过酶法从年轻小鼠中分离出来，并用于高质量的电流电压钳记录，这些电流是用通道特异性阻断剂间接分离的。电流将由动作电位波形组成的电压钳命令诱发，允许直接测量促成放电的电流。在视觉控制下，小脑切片将用于记录小脑核神经元对浦肯野神经元中诱发的高频和低频放电的反应。在特定的神经元类的电流的实验措施是必不可少的神经活动的准确的计算机模型的发展，以及小脑功能和功能障碍的系统水平的研究的细胞解释。

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.