Electrophysiological And Pathological Study On Transesophageal Degeneration Of Post - Stroke Sports System In Rats

Background:It has been demonstrated that transsynaptic degeneration occured in substantia nigra, thalamus and vision system after nerve fibers from cerebral cortex impaired. However, it is not clear whether transsynaptic degeneration happens in spinal motor neurons after corticospinal tract injury. Several clinical studies reported that the electrophysiology of the paretic limb in stroke patients was abnormal, suggesting the transsynaptic degeneration of lower motor neuron was existed. But there were no such evidence provided by pathologic studies of the spinal cord, neither in animal models nor in human autopsy. The study on the spinal ventral neurons after stroke, helps understanding the mechanism of muscle atrophy in stroke patients, which can direct the subsequent rehabilitative therapy.Objectives:(1) To evaluate the change of the paretic lower limbs electrophysiological results in MCAO SD rats.(2) To investigate the changes of spinal neurons, and to determine whether transsynaptic degeneration exists.(3) To analyze the relations between electrophysiological and pathological data, study on the mechanism of transsynaptic degeneration in motor system after stroke preliminarily.Methods:5groups of subjects including controls, MCAO rats died at1st day, MCAO rats died at7th day, MCAO rats died at14th day, were tested electromyelography, motor nerve conduction velocity and motor unit number estimations in paretic posterior tibial muscles. At the same time, modified Neurological Severity Score was also evaluated. After tests, Bax, Bcl-2and NeuN stainings were performed in lumbar spine to investigate whether spinal neurons have apoptosis or degeneration, and GFAP staining was to evaluate the changes of astrocytes. The features of limb electrophysiology and spinal pathology were also analyzed.Results:(1) The frequency of spontaneous activity in paretic limb was14.6%; the frequency of spontaneous activity in mNSS≥7group was30%(6/20), which was6.3%(1/16) in mNSS<7group.(2) After MCAO, the CMAP amplitude in paretic side was significantly smaller than the nonparetic side at24hours (61.75±10.38vs65.86±8.87, P<0.05) and7days (60.60±8.14vs66.83±9.74, P<0.05).(3)7days after MCAO, the paretic side MUNE was significantly less than the nonparetic side (381±83.0vs441±89.7, P<0.05).(4) Compared to the controls, the ventral neurons were significantly decreased at14th day (5.1±1.29vs7.3±1.75, P<0.05), while Bax and Bcl-2positive ventral neurons were increased significantly at1st day, and GFAP positive astrocytes were increased at1st and7th day.Conclusion:(1) Abnormal spontaneous activity was found in paretic limb in MCAO rats, and CMAP amplitude and MUNE in paretic side were significantly smaller than the nonparetic side, which suggested that upper motor neurons injury after stroke could affect the lower motor neurons may through transsynaptic degeneration.(2) The decreased number of ventral neurons and high expression of apoptosis associated proteins suggested that transsynaptic degeneration in motor system could be existed. And astrocytes activation could be related to the initiation and development of transsynaptic degeneration.(3) After corticospinal tract injury, neurological severity and the course of stroke may affect transsynaptic degeneration.