Regulation of motor neuron dendrite growth by NMDA receptor activation.
Regulation of motor neuron dendrite growth by NMDA receptor activation.
复制标题
作者：
R. Kalb
脊髓运动神经元在发育过程中在形态、电生理和分子组成方面经历巨大变化。其中一些成熟发生在出生后，当四肢用于运动时，这表明神经元活动可能会影响运动神经元的发育。为了确定可能受活动调节的运动神经元的特征，我们首先检查了用霍乱毒素缀合的辣根过氧化物酶标记的大鼠运动神经元细胞体和树突树的结构发育。运动神经元细胞体以及径向轴和头尾轴的树突在生命的第一个月内逐渐生长。相反，树突乔木/细胞的生长和树突分支的数量是双相的，过度生长，然后退化，直到达到成年模式。接下来我们研究了神经传递对这些运动神经元特征发育的影响。我们发现，谷氨酸受体的 N-甲基-D-天冬氨酸（NMDA）亚型的拮抗作用抑制了出生后早期的细胞体生长和树突分支，但对径向轴和头尾轴树突生长的最大范围没有影响。 NMDA 受体拮抗作用对运动神经元及其树突的影响暂时受到限制；我们对树突结构的所有解剖测量都对成人的 NMDA 受体拮抗作用具有抵抗力。这些结果表明，成熟运动神经元树突结构的建立部分是由于出生后早期敏感时期响应传入输入的树突生长所致。
Spinal motor neurons undergo great changes in morphology, electrophysiology and molecular composition during development. Some of this maturation occurs postnatally when limbs are employed for locomotion, suggesting that neuronal activity may influence motor neuron development. To identify features of motor neurons that might be regulated by activity we first examined the structural development of the rat motor neuron cell body and dendritic tree labeled with cholera toxin-conjugated horseradish peroxidase. The motor neuron cell body and dendrites in the radial and rostrocaudal axes grew progressively over the first month of life. In contrast, the growth of the dendritic arbor/cell and number of dendritic branches was biphasic with overabundant growth followed by regression until the adult pattern was achieved. We next examined the influence of neurotransmission on the development of these motor neuron features. We found that antagonism of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor inhibited cell body growth and dendritic branching in early postnatal life but had no effect on the maximal extent of dendrite growth in the radial and rostrocaudal axes. The effects of NMDA receptor antagonism on motor neurons and their dendrites was temporally restricted; all of our anatomic measures of dendrite structure were resistant to NMDA receptor antagonism in adults. These results suggest that the establishment of mature motor neuron dendritic architecture results in part from dendrite growth in response to afferent input during a sensitive period in early postnatal life.