Sensory gating of an embryonic zebrafish interneuron during spontaneous motor behaviors
Sensory gating of an embryonic zebrafish interneuron during spontaneous motor behaviors
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DOI：
10.3389/fncir.2014.00121
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发表时间：
2014-09-30
影响因子：
3.5
通讯作者：
Drapeau, Pierre
中科院分区：
文献类型：
--
作者：
Knogler, Laura D.;Drapeau, Pierre
除了最简单的单突触反射弧外，所有的感觉刺激都是由感觉神经元编码的，感觉神经元通过感觉中间神经元将信号传递给下游的伙伴，以引起反应。在斑马鱼胚胎(Danio Rerio)中，皮肤Rohon-Beard(Rb)感觉神经元对机械刺激做出反应，并兴奋下游的谷氨酸能连合初级上升(COPA)中间神经元，产生对侧刺激部位的屈曲反应。在没有感觉刺激的情况下，斑马鱼的脊髓运动回路在发育过程中会自发地激活，这是由于起搏器的活动导致躯干的重复卷曲。因此，必须将自身产生的运动与外部刺激区分开来，以确保适当地激活触摸反射。在这里，我们记录了自发和诱发的虚构运动行为中的COPAS，以检验对自我运动的反应是如何在感觉中间神经元中进行门控的。在自发缠绕期间，COPAS接收到与对侧屈曲一致的甘氨酸能输入，在缠绕事件的持续时间内分流放电。COPAs的分流失活是由于氯离子电导缓慢失活导致膜电阻降低和动作电位阈值升高所致。在后来发展起来的自发突发性游泳过程中，COPAS接收到与同侧运动神经元兴奋同相的甘氨酸能输入，并提供持续的分流。在触摸刺激期间，短潜伏期谷氨酸能输入产生通过AMPA受体的阳离子电流，在分流抑制开始之前驱动COPA中的单个大幅度动作电位，为下游神经元的激活提供了一个短暂的窗口。我们比较了COPAS与其他脊髓神经元的特性，认为COPAS上的甘氨酸能信号作为运动中反射抑制的必然放电信号。
In all but the simplest monosynaptic reflex arcs, sensory stimuli are encoded by sensory neurons that transmit a signal via sensory interneurons to downstream partners in order to elicit a response. In the embryonic zebrafish (Danio rerio), cutaneous Rohon-Beard (RB) sensory neurons fire in response to mechanical stimuli and excite downstream glutamatergic commissural primary ascending (CoPA) interneurons to produce a flexion response contralateral to the site of stimulus. In the absence of sensory stimuli, zebrafish spinal locomotor circuits are spontaneously active during development due to pacemaker activity resulting in repetitive coiling of the trunk. Self-generated movement must therefore be distinguishable from external stimuli in order to ensure the appropriate activation of touch reflexes. Here, we recorded from CoPAs during spontaneous and evoked fictive motor behaviors in order to examine how responses to self-movement are gated in sensory interneurons. During spontaneous coiling, CoPAs received glycinergic inputs coincident with contralateral flexions that shunted firing for the duration of the coiling event. Shunting inactivation of CoPAs was caused by a slowly deactivating chloride conductance that resulted in lowered membrane resistance and increased action potential threshold. During spontaneous burst swimming, which develops later, CoPAs received glycinergic inputs that arrived in phase with excitation to ipsilateral motoneurons and provided persistent shunting. During a touch stimulus, short latency glutamatergic inputs produced cationic currents through AMPA receptors that drove a single, large amplitude action potential in the CoPA before shunting inhibition began, providing a brief window for the activation of downstream neurons. We compared the properties of CoPAs to those of other spinal neurons and propose that glycinergic signaling onto CoPAs acts as a corollary discharge signal for reflex inhibition during movement.