Heaton M B, Paiva M
Dev Biol. 1986 Aug;116(2):314-8. doi: 10.1016/0012-1606(86)90134-x.
In a previous study, explants from the neural tube of 2-day chick embryos, containing the trigeminal motor nucleus, showed specific enhancement of neurite outgrowth in the presence of culture medium conditioned by target musculature of an age at which innervation would normally be taking place in vivo. In the present study, similar explants were grown in the presence of target-conditioned medium from midincubation (10-day) embryos and late-incubation (18-day) embryos. At both of these later developmental stages, the target muscle-conditioned medium failed to produce enhanced neurite outgrowth. Rather, fewer processes were extended from the trigeminal explants in both experimental conditions compared to control cultures. This inhibitory effect was statistically significant in some cases, and did not appear to be related to the amount of target-conditioned medium present. It is concluded that trophic influences on nerve fiber outgrowth by target tissue are stage-specific in this system, and it is speculated that inhibitory influences such as those demonstrated may interact with excitatory influences in the normal patterning of the developing nervous system.
在先前的一项研究中，取自2日龄鸡胚神经管、包含三叉神经运动核的外植体，在存在由体内正常进行神经支配时的目标肌肉组织条件培养液的情况下，显示出神经突生长的特异性增强。在本研究中，类似的外植体在来自孵化中期（10日龄）胚胎和孵化后期（18日龄）胚胎的目标条件培养液存在下生长。在这两个较晚的发育阶段，目标肌肉条件培养液均未能使神经突生长增强。相反，与对照培养物相比，在两种实验条件下三叉神经外植体伸出的突起均较少。这种抑制作用在某些情况下具有统计学意义，并且似乎与存在的目标条件培养液的量无关。得出的结论是，在该系统中，目标组织对神经纤维生长的营养影响是阶段特异性的，并且推测诸如所证明的抑制性影响可能在发育中的神经系统的正常模式形成中与兴奋性影响相互作用。
