Chandran A P, Oda K, Shibasaki H
Department of Physiology, Medical College, Rohtak, India.
Brain Dev. 1991 May;13(3):180-3. doi: 10.1016/s0387-7604(12)80026-x.
H-reflex recovery, H-amplitude and H/M ratio were recorded in 54 mice aged 3-12 weeks to study the motoneuron excitability and changes in it during various stages of development. The H-reflex recovery curve at 12 wk showed 3 phases: an early, relative facilitation (before 10 ms), an almost total inhibition at 10 ms and a rapid recovery thereafter. At 3 wk, however, there was only slow recovery after 10 ms and the H-reflex recovery was significantly low during the 40-100 ms period as compared to those in the other age groups, indicating that between 3 and 6 wk, there was a significant increase in the motoneuron excitability. The H-reflex amplitude also showed a significant increase during the 3-6 wk period. However, the H/M ratio did not show any significant increase either during the 3-6 wk period or thereafter. It is concluded that the H-reflex recovery at 3 wk suggests hypoexcitability of the motoneurons, possibly due to immaturity. Since there was a significant increase in the H-reflex recovery during the 3-6 wk period without any parallel increase in the H/M ratio, it is concluded that presynaptic and polysynaptic mechanisms acting on the motoneurons develop during this period. The increase in the H-reflex amplitude is possibly due to the increase in the muscle mass. The H-reflex recovery pattern at 12 wk, without the phase of late inhibition observed in man, is suggestive of less supra-spinal control mechanisms acting upon the motoneurons.
记录了54只3至12周龄小鼠的H反射恢复情况、H波幅和H/M比值，以研究运动神经元兴奋性及其在不同发育阶段的变化。12周龄小鼠的H反射恢复曲线呈现三个阶段：早期相对易化（10毫秒之前）、10毫秒时几乎完全抑制以及此后的快速恢复。然而，3周龄时，10毫秒后仅出现缓慢恢复，且在40至100毫秒期间，H反射恢复明显低于其他年龄组，这表明在3至6周龄期间，运动神经元兴奋性显著增加。H反射波幅在3至6周龄期间也显著增加。然而，H/M比值在3至6周龄期间及之后均未出现任何显著增加。结论是，3周龄时的H反射恢复提示运动神经元兴奋性降低，可能是由于不成熟所致。由于在3至6周龄期间H反射恢复显著增加，而H/M比值没有相应增加，因此得出结论，在此期间作用于运动神经元的突触前和多突触机制得以发展。H反射波幅增加可能是由于肌肉量增加。12周龄时的H反射恢复模式，没有人类中观察到的晚期抑制阶段，提示作用于运动神经元的脊髓上控制机制较少。
