Lennerstrand G, Baker R
Department of Ophthalmology, Karolinska Institute, Huddinge Hospital, Stockholm, Sweden.
Acta Physiol Scand. 1987 Nov;131(3):361-9. doi: 10.1111/j.1748-1716.1987.tb08251.x.
Mechanical characteristics and electrical activity were studied in the extraocular muscles of the catfish, Ictalurus punctatus. The contractile properties were determined by stimulation of the individual muscle nerve branches to lateral and medial rectii and the superior and inferior oblique muscles. The speed of contraction was higher than in most other fish muscle, with a twitch contraction time of about 12 ms and a tetanus fusion frequency of 150-170 Hz in all four eye muscles. The fatigue resistance was also high. These properties were the same in fully innervated and partially innervated muscle, largely irrespective of what part of the muscle that was activated. Although different fibre types are known to exist in fish extraocular muscle, it was not possible to obtain functional separation of the mechanical force profile even in the lateral rectus with two distinct motoneuronal innervations. We suggest that polyneuronal innervation of the muscle fibres produces the mechanical responses. Since EMG activity during spontaneous eye movements was similar in the global and the orbital parts of the muscle, all types of fibres in fish extraocular muscle are probably recruited for all types of eye movements.
对斑点叉尾鮰的眼外肌的力学特性和电活动进行了研究。通过刺激外直肌、内直肌、上斜肌和下斜肌的单个肌肉神经分支来测定收缩特性。收缩速度高于大多数其他鱼类肌肉，所有四条眼肌的单收缩时间约为12毫秒，强直融合频率为150 - 170赫兹。抗疲劳能力也很强。在完全神经支配和部分神经支配的肌肉中，这些特性是相同的，很大程度上与激活肌肉的哪一部分无关。虽然已知鱼类眼外肌存在不同的纤维类型，但即使在具有两种不同运动神经元支配的外直肌中，也无法实现机械力分布的功能分离。我们认为肌肉纤维的多神经元支配产生了机械反应。由于在自发眼动过程中，肌肉整体部分和眼眶部分的肌电图活动相似，鱼类眼外肌的所有纤维类型可能在所有类型的眼动中都会被募集。
