Structure and synaptic function of local reflex circuit for crayfish uropod motor control system

研究的目的是了解局部回路神经元的功能作用和与行为背景相关的神经回路的基本组织。机械刺激对克氏原螯虾尾鳍产生“飞镖”样回避反应。小龙虾关闭两个尾足类动物和腹部的延伸向前走。尾足的运动是由局部环路神经元（包括非棘突神经元、棘突神经元和上行神经元）介导的，本文用细胞内同步记录和染色的方法详细研究了回避反应中与非棘突神经元的突触联系。一些nonspiking本地interneurons接受兴奋性外感受性感觉输入直接从头发传入。上行和尖峰局部中间神经元也通过化学突触接受传入神经的直接输入。运动神经元与传入神经元之间既没有直接联系，也没有来自毛传入神经元的直接抑制联系，毛传入神经元的抑制性输入通过局部棘突神经元传递到非棘突神经元。间接兴奋性输入从毛传入也被传输到nonspiking interneurons的节间上行神经元。一些非发放神经元与其他非发放神经元之间存在兴奋性或抑制性联系。非尖峰局部中间神经元的膜电位变化，反过来，有效地改变尾足运动神经元的膜电位通过逐渐释放的化学递质。

The aim of research is to understand the functional role of local circuit neurones and fundamental roganization of neural circuit relating to behavioral context. Mechanical stimulation of the tailfan in crayfish procambarus clarkii elicits a "dart" -like avoidance reaction. The crayfish closed both uropods and walks forward with extension of the abdomen. The movement of the uropod is mediated by local circuit neurones, including nonspiking and spiking local interneurones and ascending interneurones.Synaptic connection to and from nonspiking local interneurones in the avoidance reaction is investigated in detail by using simultaneous intracellular recordings and stainings. Some nonspiking local interneurones received excitatory exteroceptive sensory inputs directly from hair afferents. Boththe ascending and spiking local interneurones also received direct inputs from the afferents via chemical synapses. Neither direct connection between motor neurones and afferents nor direct inhibitory connection from hair afferents were detected.Inhibitory inputs from hair afferents were transmitted ento nonspiking interneurones via mediated by spiking local interneurones. Indirect excitatory inputs from hair afferents were also transmitted into nonspiking interneurones by intersegmental ascending interneurones. Some nonspiking interneurones made either excitatory or inhibitory connection with other nonspiking interneurones. Membrane potential change of nonspiking local interneurones was, in turn, effective to change the membrane potential of uropod motor neurones by means of gradual release of chemical transmitters.