Optical mapping/imaging of neural activity in the spinal cord : investigation for possible mechanisms of dysesthesia

为了探讨感觉障碍的可能机制，我们使用多点光学记录/成像技术研究了胚胎和成年脊髓中神经元通路/网络活动的时空模式。在胚胎实验中，从鸡和大鼠胚胎中分离脊髓，并制备横切片，其中第13颈髓神经或第2或第5腰椎脊神经完整。用电压敏感型花菁染料(NK2761)对切片进行染色。利用128或1020个单元的光电二极管阵列，用正方电流脉冲刺激脊神经，同时记录了制备过程中多个部位的跨膜电压相关光学(染料吸光度)变化。从对应于灰质后部(背部)和前部(腹部)的背侧和腹侧区域检测到视觉反应。光信号由两个C…组成成分更多，快尖峰和慢信号。在背侧，快的棘样信号为感觉神经的突触前动作电位，慢的信号为突触后电位。在腹侧，快速的棘波状信号反映运动神经元的逆行动作电位，而慢信号与运动神经元诱发的突触后电位有关。在成年脊髓实验中，我们考察了刺激脊髓神经在活体大鼠脊髓内诱发内源性光学成像的可行性。成年大鼠用乌拉坦麻醉，d-管胡萝卜碱固定。C5~Th1椎板切除暴露颈髓。解剖正中神经和尺神经，在前肢植入双极电极。使用差动视频采集系统记录脊髓对正中神经和尺神经刺激时的光反射变化。在颈髓背侧，在C6和C8之间可以清晰地检测到内源性光信号，并且信号的幅度随刺激强度的增加而增加。刺激外周神经在颈髓背侧引起的反应可能是后角初级传入神经元和突触后神经元的神经活动。较少

To examine the possible mechanisms for dysesthesia, we investigated spatiotemporal patterns of neuronal pathway/network activity in embryonic and adult spinal cords, using multiple-site optical recording/imaging techniques.In experiments using embryos, spinal cords were dissected from chick and rat embryos, and transverse slice preparations were prepared with the 13th cervical spinal nerve or with the 2nd or 5th lumbosacral spinal nerve intact. The slice preparations were stained with a voltage-sensitive merocyanine-rhodanine dye (NK2761). Transmembrane voltage-related optical (dye-absorbance) changes evoked by spinal nerve stimulation with positive square current pulses using a suction electrode were recorded simultaneously from many loci in the preparation, using a 128- or 1020-element photodiode array. Optical responses were detected from dorsal and ventral regions corresponding to the posterior (dorsal) and anterior (ventral) gray matters. The optical signals were composed of two c … More omponents, fast spike-like and slow signals. In the dorsal region, the fast spike-like signal was identified as the presynaptic action potential in the sensory nerve, and the slow signal as the postsynaptic potential. In the ventral region, the fast spike-like signal reflected the antidromic action potential in motoneurons, and the slow signal was related to the postsynaptic potential evoked in the motoneuron.In experiments using adult spinal cords, we made an examination of the feasibility of an intrinsic optical imaging evoked by spinal nerve stimulation in the in vivo rat spinal cord. Adult rats were anesthetized by Urethane and immobilized by d-tubocurarine. Laminectomy was performed between C5 and Th1 to expose the cervical spinal cord. Median and ulnar nerves were dissected and bipolar electrodes were implanted in the forelimb. Changes in optical reflectance were recorded from spinal cord in response to median and ulnar nerve stimulation using a differential video acquisition system. In the dorsal region of the cervical spinal cord, the intrinsic optical signals were detected clearly between C6 and C8, and the amplitude of the signals increased in proportion to the intensity of stimulation. The response evoked by peripheral nerve stimulation in the dorsal cervical spinal cord is suggested to be neural activities of the primary afferent and the postsynaptic neurons in the dorsal horn. Less