Phelps P E, Barber R P, Vaughn J E
Division of Neurosciences, Beckman Research Institute of the City of Hope, Duarte, California 91010-0269.
J Comp Neurol. 1991 May 1;307(1):77-86. doi: 10.1002/cne.903070108.
This investigation focused on the relationship between neurotransmitter phenotype expression and rat motor neuron development, as studied with choline acetyltransferase (ChAT) immunocytochemical techniques. The development of two subclasses of motor neurons, somatic and autonomic efferents, was examined in the upper thoracic spinal cord. ChAT was first detected in a few neurons on embryonic day 12 1/2 (E12 1/2), and in numerous cells located in a single, ventrolaterally located column in the intermediate zone on E13. By E14, this group of ChAT-positive neurons was more intensely immunoreactive, and their axons could be traced to appropriate targets in developing somatic muscle and paravertebral sympathetic ganglia. During the E15-16 period, somatic and autonomic motor neurons separated into two distinct subgroups, with the latter cells being observed to translocate dorsally. By E17, these autonomic motor neurons reached their final positions in the midportion of the intermediate zone. The autonomic motor neurons were observed to extend transverse dendritic bundles across the spinal cord between E15-16, but evidence of the longitudinal bundles of sympathetic preganglionic dendrites was not observed until after birth. A recent study of cholinergic thoracic motor neurons found that both somatic and autonomic cells were generated synchronously during the E11-12 period (Barber et al., Soc Neurosci Abstr 15:588, 1989). In combination with the present results, these data indicate that no more than 1 1/2 days are necessary after motor neuron genesis before a few cells begin to express detectable levels of ChAT, and that no more than 2 days are required before large numbers express this marker of the cholinergic phenotype. Further comparisons of the present findings with those of previous investigations of the development of both somatic and autonomic motor neurons (Dennis et al., Dev Biol 81:266, 1981; Rubin, J Neurosci 5:685, 697, 1985) indicate that these cells contain ChAT at the time their axons are growing toward their respective peripheral targets 1 day before the time when physiological evidence of function is manifest. Furthermore, the present results suggest that both subclasses of motor neurons initially migrate together from the ventricular zone into a single motor column within the ventral intermediate zone, and that the autonomic neurons subsequently translocate dorsally. Thus, autonomic motor neurons appear to be an exception to the generalization that postmitotic neurons migrate directly from the germinal zone to their final positions within the central nervous system.
本研究聚焦于神经递质表型表达与大鼠运动神经元发育之间的关系，采用胆碱乙酰转移酶（ChAT）免疫细胞化学技术进行研究。在胸段上段脊髓中，对运动神经元的两个亚类，即躯体传出神经元和自主传出神经元的发育进行了检测。ChAT最早在胚胎第12.5天（E12.5）的少数神经元中被检测到，在E13时，位于中间带腹外侧单一柱状结构中的大量细胞中也能检测到。到E14时，这群ChAT阳性神经元的免疫反应性更强，其轴突可追踪到发育中的躯体肌肉和椎旁交感神经节中的相应靶标。在E15 - 16期，躯体和自主运动神经元分为两个不同的亚组，观察到后者的细胞向背侧移位。到E17时，这些自主运动神经元到达中间带中部的最终位置。观察到自主运动神经元在E15 - 16期间在脊髓内延伸横向树突束，但直到出生后才观察到交感节前树突纵向束的证据。最近一项关于胆碱能胸段运动神经元的研究发现，躯体和自主细胞在E11 - 12期同步产生（Barber等人，《神经科学学会摘要》15:588，1989）。结合本研究结果，这些数据表明，运动神经元发生后，不超过1.5天就有少数细胞开始表达可检测水平的ChAT，不超过2天就有大量细胞表达这种胆碱能表型标记物。将本研究结果与先前关于躯体和自主运动神经元发育的研究结果（Dennis等人，《发育生物学》81:266，1981；Rubin，《神经科学杂志》5:685，697，1985）进一步比较表明，这些细胞在其轴突向各自外周靶标生长时就含有ChAT，比功能生理证据出现的时间早1天。此外，本研究结果表明，运动神经元的两个亚类最初一起从室带迁移到腹侧中间带内的单个运动柱，自主神经元随后向背侧移位。因此，自主运动神经元似乎是有丝分裂后神经元直接从生发区迁移到中枢神经系统内最终位置这一普遍规律的一个例外。
