Miyata Y, Kashihara Y, Homma S, Kuno M
J Neurosci. 1986 Jul;6(7):2012-8. doi: 10.1523/JNEUROSCI.06-07-02012.1986.
Sensory neurons with small diameters (A delta and C cells) are known to be responsive to exogenous NGF even at postnatal stages. We have examined whether large Group Ia sensory neurons (A alpha cells) arising from muscle spindles are also responsive to NGF in neonatal rats. For this purpose, monosynaptic excitatory postsynaptic potentials (EPSPs) were evoked in spinal motoneurons by Group Ia muscle afferent volleys. When a muscle nerve was crushed on the day after birth, the monosynaptic EPSPs elicited by afferent volleys from the muscle were depressed within several weeks. This synaptic depression was partially reversed by daily treatment with NGF. NGF treatment also enhanced the EPSPs evoked by stimulation of intact muscle nerves, but this effect was less marked than that on the EPSPs produced by stimulation of the previously crushed muscle nerve. Exogenous NGF was effective for the EPSPs when the treatment began on the day after birth but not when the treatment began 4 d after birth. Following crush of a muscle nerve on the day after birth, about 45% of the sensory neurons derived from the muscle were lost. The cell death of small sensory neurons was prevented by daily treatment with NGF, whereas the NGF treatment was ineffective in preventing the cell death of large sensory neurons. The results indicate that Group Ia sensory neurons are responsive to NGF during early postnatal life.
已知直径较小的感觉神经元（Aδ和C细胞）即使在出生后阶段也对外源性神经生长因子（NGF）有反应。我们研究了来自肌梭的大型Ia类感觉神经元（Aα细胞）在新生大鼠中是否也对NGF有反应。为此，通过Ia类肌肉传入冲动在脊髓运动神经元中诱发单突触兴奋性突触后电位（EPSP）。当在出生后第一天挤压肌肉神经时，来自该肌肉的传入冲动诱发的单突触EPSP在几周内受到抑制。每天用NGF治疗可部分逆转这种突触抑制。NGF治疗还增强了刺激完整肌肉神经诱发的EPSP，但这种作用不如刺激先前挤压过的肌肉神经所产生的EPSP明显。当在出生后第一天开始治疗时，外源性NGF对EPSP有效，但在出生后4天开始治疗时则无效。出生后第一天挤压肌肉神经后，约45%源自该肌肉的感觉神经元丢失。每天用NGF治疗可防止小感觉神经元的细胞死亡，而NGF治疗对防止大感觉神经元的细胞死亡无效。结果表明，Ia类感觉神经元在出生后早期对NGF有反应。
