ボツリヌス毒素による外眼筋の形態変化

Morphological alterations in extraocular muscles induced by botulinum toxin

　ウサギの外眼筋の筋線維の形態に対するボツリヌス毒素注入の影響を検討した。4匹には10単位，5匹には5単位のA型ボツリヌス毒素（BOTOX^®）を右眼の上直筋に注入し，左眼の上直筋には対照として生理食塩水を注入した。注入3日，1,3，および5週後に眼窩および中間層の筋線維の径を組織標本上で光学顕微鏡を用いて計測した。10単位のボツリヌス毒素の注入1週後では，眼窩層筋線維の径は対照に比べて小さくなったが，5週後では筋線維の肥大が認められた。しかし，中間層の筋線維については明らかな変化は認められなかった。一方，5単位注入では眼窩層，および中間層ともに筋線維の大きさに明らかな変化は認められなかった。

We studied morphological changes in rabbit extraocular muscles following pharmacological denervation induced by botulinum toxin. Experiments were performed in 9 rabbits (weight range: 1.6 to 3.0 kg) anesthetized with sodium pentobarbital. In four rabbits, 10 units and in five rabbits, 5 units of botulinum toxin type A (BOTOX^® ) was injected into the superior rectus muscle of the right eye. Saline was injected into the superior rectus muscle of the left eye as control. Three days, 1, 3 and 5 weeks later, the diameter of the myofiber of the orbital and intermediate layers was measured on histological sections using light microscope. Injection of 10 units of botulinum toxin produced morphological alterations during the observa-tion period. After 1 week, the diameter of the myofiber in the orbital layer was reduced, but after 5 weeks these muscle fibers were hypertrophied compared to that of the control eyes. No apparent changes were observed in the intermediate layer muscle fiber. With 5 units of botulinum toxin, no morphological changes were observed in the orbital or intermediate layer.