Foehring R C, Sypert G W, Munson J B
J Neurophysiol. 1986 May;55(5):931-46. doi: 10.1152/jn.1986.55.5.931.
This work tested whether the membrane electrical properties of cat motoneurons, the contractile properties of their muscle units, and the normal relationships among them would be restored 9 mo after section and resuture of their muscle nerve. Properties of medial gastrocnemius (MG) motor units were examined 9 mo following section and resuture of the MG nerve in adult cats. Motoneuron electrical properties and muscle-unit contractile properties were measured. Motor units were classified on the basis of their contractile properties as type fast twitch, fast fatiguing (FF), fast twitch with intermediate fatigue resistance (FI), fast twitch, fatigue resistant (FR), or slow twitch, fatigue resistant (S) (8, 20). Muscle fibers were classified as type fast glycolytic (FG), fast oxidative glycolytic (FOG), or slow oxidative (SO) on the basis of histochemical staining for myosin adenosine triphosphatase, nicotinamide adenine dinucleotide diaphorase, and alpha-glycerophosphate dehydrogenase (48). Following 9 mo self-reinnervation, the proportions of each motor-unit type were the same as in normal control animals. Motoneuron membrane electrical properties [axonal conduction velocity, afterhyperpolarization (AHP) half-decay time, rheobase, and input resistance] also returned to control levels in those motoneurons that made functional reconnection with the muscle (as determined by ability to elicit measurable tension). The relationships among motoneuron electrical properties were normal in motoneurons making functional reconnection. Approximately 10% of MG motoneurons sampled did not elicit muscle contraction. These cells' membrane electrical properties were different from those that did elicit muscle contraction. Contractile speed and fatigue resistance of reinnervated muscle units had recovered to control levels at 9 mo postoperation. Force generation did not recover fully in type-FF units. The reduced tensions were apparently due to failure of recovery of FG muscle fiber area. Following reinnervation, relationships between motoneuron electrical and muscle-unit contractile properties were similar to controls. This was reflected in a degree of correspondence between motor-unit type and motoneuron type similar to normal units (84 vs. 86%, as defined by Ref. 61). There was a significantly increased proportion of type-SO muscle fibers and a decrease in the fast muscle fibers (especially type FOG) in 9 mo reinnervated MG. Together with the unchanged proportions of motor-unit types, this led to an estimate of average innervation ratios being increased in type-S motor units and decreased in type-FR units.(ABSTRACT TRUNCATED AT 400 WORDS)
本研究检测了猫运动神经元的膜电特性、其肌肉单位的收缩特性以及它们之间的正常关系在肌肉神经切断并重新缝合9个月后是否会恢复。在成年猫的腓肠肌内侧（MG）神经切断并重新缝合9个月后，检测了MG运动单位的特性。测量了运动神经元的电特性和肌肉单位的收缩特性。根据收缩特性，运动单位被分类为快肌纤维、快速疲劳型（FF）、具有中等疲劳抗性的快肌纤维型（FI）、抗疲劳的快肌纤维型（FR）或慢肌纤维、抗疲劳型（S）（8,20）。根据肌球蛋白三磷酸腺苷酶、烟酰胺腺嘌呤二核苷酸黄递酶和α-甘油磷酸脱氢酶的组织化学染色，肌肉纤维被分类为快糖酵解型（FG）、快氧化糖酵解型（FOG）或慢氧化型（SO）（48）。在9个月的自我重新神经支配后，每种运动单位类型的比例与正常对照动物相同。在那些与肌肉建立功能性重新连接的运动神经元中（通过引发可测量张力的能力确定），运动神经元膜电特性[轴突传导速度、超极化后电位（AHP）半衰期、基强度和输入电阻]也恢复到对照水平。在建立功能性重新连接的运动神经元中，运动神经元电特性之间的关系正常。所采样的MG运动神经元中约10%未引发肌肉收缩。这些细胞的膜电特性与那些引发肌肉收缩的细胞不同。重新神经支配后肌肉单位的收缩速度和抗疲劳性在术后9个月已恢复到对照水平。FF型单位的力量产生未完全恢复。张力降低显然是由于FG肌纤维面积未能恢复。重新神经支配后，运动神经元电特性与肌肉单位收缩特性之间的关系与对照相似。这反映在运动单位类型与运动神经元类型之间的对应程度与正常单位相似（84%对86%，如参考文献61所定义）。在9个月重新神经支配的MG中，SO型肌纤维的比例显著增加，快肌纤维（尤其是FOG型）减少。连同运动单位类型比例不变，这导致估计S型运动单位的平均神经支配率增加，FR型单位的平均神经支配率降低。（摘要截断于字）
