Fladby T
Acta Physiol Scand. 1987 Feb;129(2):229-38. doi: 10.1111/j.1748-1716.1987.tb08063.x.
Using conventional physiological techniques for measuring unitary contractions and end-plate potentials (epps), the number, size and segmental properties of motor units (MUs) in the soleus muscle of the mouse during postnatal development have been examined. The number of MUs remains constant after birth, and there is no evidence of segmental preferences in the innervation pattern, before, during or after the postnatal elimination of redundant terminals. In neonates, MU size estimates based on twitch contractions are 30% smaller than tetanic estimates. Intracellular recording of epps shows that this is caused by facilitation of epps on repetitive stimulation. The frequency of occurrence of epps in the muscle from a few, isolated motor axons shows that the average motoneuron contacts 36% of the fibres in the muscle neonatally. A substantial fraction of the contacts is subthreshold for twitch activation of their fibre. The MU size remains constant up to day 5. During the next 10 days, the MU size is reduced to the mature value of 5% of the fibres in the muscle. It is concluded that the neonatal loss of synaptic terminals in this muscle takes place without concomitant loss of entire motor neurons, and that it is independent of possible segmental preferences in the innervation of the muscle.
运用传统生理学技术测量单收缩和终板电位（epps），对出生后发育过程中小鼠比目鱼肌运动单位（MUs）的数量、大小和节段特性进行了研究。出生后运动单位的数量保持不变，并且在出生后冗余终末消除之前、期间或之后，在神经支配模式中没有节段偏好的证据。在新生儿中，基于单收缩的运动单位大小估计值比强直收缩估计值小30%。对终板电位的细胞内记录表明，这是由于重复刺激时终板电位的易化作用所致。来自少数孤立运动轴突的肌肉中终板电位的出现频率表明，新生时平均运动神经元接触肌肉中36%的纤维。相当一部分接触对于其纤维的单收缩激活来说是阈下的。运动单位大小在第5天之前保持不变。在接下来的10天里，运动单位大小减小至肌肉中纤维的5%这一成熟值。得出的结论是，该肌肉中突触终末在新生儿期的丧失发生时，整个运动神经元并未随之丧失，并且它与肌肉神经支配中可能存在的节段偏好无关。
