Shall M S, Sorg P J, McClung J R, Gilliam E E, Goldberg S J
Department of Physical Therapy, Medical College of Virginia, Commonwealth University, Richmond, VA 23298-0224, USA.
Acta Anat (Basel). 1995;153(2):151-60. doi: 10.1159/000313649.
Physiologically, the contractile characteristics and electromyography (EMG) of cat inferior oblique (IO) muscle fibers supplied by the medial and lateral IO muscle nerve branches were studied by direct nerve stimulation. Anatomically, the brain stem locations and sizes of IO motoneuron soma were evaluated after retrograde labeling by horseradish peroxidase (HRP) through whole IO muscle nerves and/or through each medial or lateral IO muscle nerve branch. Stimulation of the lateral nerve branch elicited significantly (p < 0.005) slower twitch contraction times (8.0 +/- 1.5 ms) and lower fusion frequencies (217 +/- 46 Hz) than when the medial branch of the IO nerve was stimulated (average twitch contraction time = 6.8 +/- 1.1 ms; average fusion frequency = 260 +/- 34 Hz). The EMG wave shape responses in the global and orbital layers could be differentiated when the individual nerve branches were stimulated, but the response differences were not consistent among animals. The average diameter of IO motoneuron soma with axons in the lateral branch of the nerve were significantly smaller (p < 0.001) than the average diameter of those IO motoneuron soma associated with the medial branch of the nerve (27.9 +/- 7.2 vs. 32.9 +/- 7.2 microns). Regardless of which nerve branch was labeled, the full range of motoneuron soma sizes was found, and these were distributed throughout the IO subdivision of the oculomotor nucleus. These findings showed that muscle contraction time and motoneuron soma diameter were correlated with the IO nerve branch subjected to stimulation or exposed to HRP. But no topographic organization of motoneurons was found within the IO division of the oculomotor nucleus.
从生理角度，通过直接神经刺激研究了由内直肌下斜肌（IO）神经分支和外直肌下斜肌神经分支支配的猫下斜肌（IO）肌纤维的收缩特性和肌电图（EMG）。从解剖学角度，通过辣根过氧化物酶（HRP）经整个IO肌神经和/或经每条内直肌或外直肌下斜肌神经分支进行逆行标记后，评估了IO运动神经元胞体在脑干中的位置和大小。与刺激IO神经的内侧分支相比（平均抽搐收缩时间 = 6.8±1.1毫秒；平均融合频率 = 260±34赫兹），刺激外侧神经分支引发的抽搐收缩时间明显更慢（p < 0.005）（8.0±1.5毫秒），融合频率更低（217±46赫兹）。当刺激单个神经分支时，全局层和眼眶层的EMG波形反应可以区分，但不同动物之间的反应差异并不一致。神经外侧分支中有轴突的IO运动神经元胞体的平均直径明显小于与神经内侧分支相关的IO运动神经元胞体的平均直径（p < 0.001）（27.9±7.2对32.9±7.2微米）。无论标记的是哪条神经分支，都发现了运动神经元胞体大小的完整范围，并且它们分布在动眼神经核的IO细分区域内。这些发现表明，肌肉收缩时间和运动神经元胞体直径与接受刺激或暴露于HRP的IO神经分支相关。但在动眼神经核的IO分区内未发现运动神经元的拓扑组织。
