Chiaia N L, Zhang S, King T D, Rhoades R W
Department of Anatomy, Medical College of Ohio, Toledo 43699.
J Comp Neurol. 1994 Jul 8;345(2):303-13. doi: 10.1002/cne.903450211.
Previous studies from this laboratory have demonstrated that prenatal damage to vibrissae follicles results in significant increases in the brainstem representations of the remaining vibrissae as demonstrated by staining for the mitochondrial enzyme cytochrome oxidase (CO). Because CO is primarily a postsynaptic marker, these results do not directly address the question of whether there were changes in the projections of primary afferent fibers. To address this issue, we made intra-axonal recordings from individual vibrissa-related primary afferents in rats that sustained damage to vibrissae follicles on embryonic day 17, and then injected horseradish peroxidase (HRP) into these axons to visualize their terminal arbors in the brainstem at the level of trigeminal subnucleus interpolaris (SpI). All vibrissae-related primary afferents responded to deflection of one and only one vibrissa, and the terminal arbors of axons (N = 47) recovered from animals that sustained fetal peripheral lesions were significantly larger than those (N = 23) from normal rats. Fibers from fetally damaged animals had increased total fiber lengths and numbers of branch points. These results indicate that reduced competition among primary afferent axons results in increases in the terminal arbors that remain. These increases occur without any significant alteration in their peripheral receptive fields.
该实验室之前的研究表明，触须毛囊的产前损伤会导致其余触须在脑干中的表征显著增加，这一点通过线粒体酶细胞色素氧化酶（CO）染色得以证明。由于CO主要是一种突触后标记物，这些结果并未直接解决初级传入纤维投射是否发生变化的问题。为了解决这个问题，我们对胚胎第17天触须毛囊受损的大鼠的单个与触须相关的初级传入纤维进行了轴突内记录，然后将辣根过氧化物酶（HRP）注入这些轴突，以观察它们在三叉神经中极核（SpI）水平的脑干终末分支。所有与触须相关的初级传入纤维仅对一根且唯一一根触须的偏转做出反应，从遭受胎儿期外周损伤的动物中恢复的轴突（N = 47）的终末分支明显大于正常大鼠的轴突（N = 23）。来自胎儿期受损动物的纤维总长度和分支点数量增加。这些结果表明，初级传入轴突之间竞争的减少导致剩余终末分支的增加。这些增加在其外周感受野没有任何显著改变的情况下发生。
