Tan U, Calişkan S
Atatürk University, Medical Faculty, Institute of Physiology, Erzurum, Turkey.
Int J Neurosci. 1988 Jan;38(1-2):151-78. doi: 10.3109/00207458809000494.
Input-output characteristics of the somatosensory system were studied in the dog. Somatosensory evoked potentials were recorded from the scalp at stimulations of the sural and gastrocnemius nerves. There was a sigmoid relationship between the stimulus strength and the amplitude of the sural nerve action potential, which was best described by a logistic equation. The early waves (P1, N1) increased especially at low threshold stimulations of the sural nerve; then they remained either unchanged or decreased at high threshold stimulations within the Group II and III ranges. The late waves (P2, N2) especially increased at high threshold Group II stimulations of the sural nerve, and increased further at strong stimuli. Similar changes were observed at stimulations of the gastrocnemius nerves. The attenuation of the early waves was explained by "gating" mechanisms acting from the sensorimotor cortex onto the sensory relay nuclei. The increase of the late waves at especially high threshold Group II and III stimulations was accounted for by the multisynaptic diffuse projection from the reticular formation and/or the nonspecific thalamic nuclei to the somatosensory cortex. In a three weeks old pup, stimulation of the gastrocnemius nerves evoked somatosensory responses with similar morphology observed in adult dogs, but the latencies of the evoked potential components were relatively long, presumably as a result of the uncompleted myelination in the somatosensory afferent system.
在犬类中研究了体感系统的输入-输出特性。在刺激腓肠神经和腓骨神经时，从头皮记录体感诱发电位。腓肠神经动作电位的刺激强度与幅度之间存在S形关系，用逻辑方程描述最为合适。早期波（P1、N1）在腓肠神经低阈值刺激时尤其增加；然后在II组和III组范围内的高阈值刺激时，它们要么保持不变，要么减小。晚期波（P2、N2）在腓肠神经II组高阈值刺激时尤其增加，在强刺激时进一步增加。在刺激腓骨神经时也观察到类似变化。早期波的衰减是由感觉运动皮层作用于感觉中继核的“闸门”机制解释的。晚期波在II组和III组尤其高阈值刺激时的增加是由网状结构和/或非特异性丘脑核向体感皮层的多突触弥散投射引起的。在3周龄幼犬中，刺激腓骨神经诱发的体感反应形态与成年犬相似，但诱发电位成分的潜伏期相对较长，推测是由于体感传入系统髓鞘形成未完成所致。
