Gregory J E, Proske U
Department of Physiology, Monash University, Clayton, Victoria, Australia.
Exp Brain Res. 1988;73(3):606-14. doi: 10.1007/BF00406620.
Discharges of muscle spindle afferents from the soleus muscle were studied in kittens aged 1-21 days and in adult cats. Vibration applied longitudinally to the tendon elicited one impulse for each cycle of vibration over the range 1-200 Hz for the kittens and up to 450 Hz for the adult. Threshold amplitudes were generally higher in the kitten than in the adult. In response to large ramp and hold stretches applied at long muscle lengths kitten spindles showed rate saturation during the length change. Dynamic index, that is the peak rate during the length change minus the rate at the final length became progressively smaller at longer muscle lengths. No sign of saturation was seen at comparable muscle lengths in the adult. It is suggested that in the newborn the bag1 intrafusal fibre is not functional and that the dynamic response is produced only by the afferent terminals on the bag2 fibre. Another difference between kitten and adult was the length sensitivity measured under dynamic conditions. This increased much more steeply with stretch rate in the kitten. One possible explanation for the higher dynamic length sensitivity is a lack of elastic fibres surrounding intrafusal fibres of immature spindles.
对1至21日龄小猫和成年猫比目鱼肌的肌梭传入纤维放电进行了研究。纵向施加于肌腱的振动，在1至200赫兹范围内，小猫每振动一个周期引发一个冲动，成年猫则高达450赫兹。小猫的阈值幅度通常高于成年猫。在长肌肉长度下施加大幅度斜坡和保持拉伸时，小猫肌梭在长度变化期间表现出频率饱和。动态指数，即长度变化期间的峰值频率减去最终长度时的频率，在更长的肌肉长度下逐渐变小。在成年猫的可比肌肉长度下未观察到饱和迹象。有人认为，新生小猫的袋1梭内纤维不起作用，动态反应仅由袋2纤维上的传入终末产生。小猫和成年猫之间的另一个差异是动态条件下测量的长度敏感性。在小猫中，这种敏感性随拉伸速率增加得更为陡峭。动态长度敏感性较高的一个可能解释是未成熟肌梭的梭内纤维周围缺乏弹性纤维。
