Fujitsuka N, Sokabe M, Yoshimura A, Ito F
Brain Res. 1987 Jul 7;415(1):144-8. doi: 10.1016/0006-8993(87)90277-0.
In some muscle spindles located in or near the red area of semitendinosus muscle of the bull frog, a fine motor axon innervates the intracapsular compact zone, without any branches onto the extrafusal muscle fibers. The fine motor axon is 3.9 microns in mean diameter (measured in living axon) and 9.8 m X s-1 in mean conduction velocity at 20 degrees C. A ramp-and-hold stretch during 20 Hz repetitive stimulation of the fine motor axon markedly increased the rate of afferent discharges during static phase. Histochemical studies indicated depletion of glycogen in a compact zone along a small diameter intrafusal muscle fiber of the muscle spindles frozen immediately after tetanic stimulation of the fine motor axon. These results suggest that the fine motor axon is a fusimotor system in the frog muscle spindle.
在牛蛙半腱肌红色区域内或附近的一些肌梭中，一条细运动轴突支配囊内致密区，而没有分支支配梭外肌纤维。这条细运动轴突的平均直径为3.9微米（在活体轴突中测量），在20摄氏度时平均传导速度为9.8米/秒。在对细运动轴突进行20赫兹重复刺激期间进行斜坡-保持拉伸，显著增加了静态期的传入放电频率。组织化学研究表明，在对细运动轴突进行强直刺激后立即冷冻的肌梭中，沿着一条小直径梭内肌纤维的致密区糖原耗尽。这些结果表明，细运动轴突是蛙肌梭中的一种肌梭运动系统。
