Matthews M A
Exp Brain Res. 1985;60(3):465-82. doi: 10.1007/BF00236932.
A normally transient ipsilateral retinofugal projection exists in the rat but is retained following eye removal because of the loss of competitive interaction between crossed and uncrossed fibers. To further explore this phenomenon, colchicine (10(-3)M) was injected into the right eye of newborn albino rats to partially suppress axonal transport in optic fibers, alter the developmental time course of retinofugal synaptic terminals and determine if this would in turn extend the period of survival of the ipsilateral projection. Measurements of the number of fibers in the nerve were also made to insure that colchicine was not lethal to the retinofugal projection. Projections into the superior colliculus were demonstrated by anterograde movement of HRP from the left eye. TMB histochemistry revealed dense labeling of the contralateral retino-recipient layers at 5 dpn in untreated or saline-injected controls. The ipsilateral projection was seen as a lighter band of activity across the colliculus which was most concentrated in the antero-medial quadrant. This pathway was transient and degenerated by 10 dpn, except for a few antero-medial fibers. Animals treated with colchicine demonstrated a retention of this pathway through 20 dpn. A concomitant quantitative analysis of synaptic development within the superior colliculus revealed populations of boutons with round (R) and flattened (F) vesicles, as well as multiple junctional (MJ) and serial (S) complexes, most of which were specialized R boutons. The various synaptic categories displayed specific ratios unique to the different stages of maturation. Intraocular colchicine reduced the ratio of R, MJ and S boutons to F terminals between 5-15 dpn (P less than 0.01). By 20 dpn, the proportions of MJ and S boutons remained depressed but the normal ratio of R to F boutons was restored. Areal determinations of each synaptic profile included in the counts revealed a significant reduction in the size of MJ synaptic profiles examined in colchicine-treated animals and this may have been reflected in the slight loss of tectal volume (6-9%). Removal of the left eye and assessment of degenerating boutons showed that the expanded ipsilateral projection was not sufficiently dense to produce such a restoration. It thus appears that colchicine delayed the growth of the R population, but the effect was reversible and this category of boutons continued to develop, albeit on a later time course.(ABSTRACT TRUNCATED AT 400 WORDS)
正常情况下，大鼠存在同侧视网膜纤维投射，但这种投射是短暂的。由于交叉和不交叉纤维之间的竞争相互作用丧失，在摘除眼球后这种投射得以保留。为了进一步探究这一现象，将秋水仙碱（10⁻³M）注入新生白化大鼠的右眼，以部分抑制视神经纤维中的轴突运输，改变视网膜纤维突触终末的发育时间进程，并确定这是否会相应延长同侧投射的存活期。还对神经中的纤维数量进行了测量，以确保秋水仙碱对视网膜纤维投射无致死作用。通过将辣根过氧化物酶（HRP）从左眼进行顺行转运，证实了向视丘的投射。TMB组织化学显示，在未处理或注射生理盐水的对照组中，5日龄时对侧视网膜接受层有密集标记。同侧投射表现为视丘上一条较淡的活性带，最集中在前内侧象限。这条通路是短暂的，到10日龄时退化，除了一些前内侧纤维。用秋水仙碱处理的动物在20日龄时仍保留了这条通路。对视丘内突触发育的同步定量分析显示，存在具有圆形（R）和平扁（F）囊泡的突触小体群体，以及多个连接（MJ）和串联（S）复合体，其中大多数是特化的R型突触小体。不同的突触类别在成熟的不同阶段呈现出独特的特定比例。眼内注射秋水仙碱降低了5 - 15日龄时R、MJ和S型突触小体与F型终末的比例（P < 0.01）。到20日龄时，MJ和S型突触小体的比例仍然较低，但R型与F型突触小体的正常比例得以恢复。对计数中包含的每个突触轮廓进行面积测定发现，秋水仙碱处理动物中检测到的MJ突触轮廓大小显著减小，这可能反映在视丘体积略有减小（6 - 9%）。摘除左眼并评估退化的突触小体表明，扩展的同侧投射密度不足以产生这种恢复。因此，秋水仙碱似乎延迟了R型突触小体群体的生长，但这种影响是可逆的，并且这类突触小体继续发育，尽管时间进程较晚。（摘要截短至400字）
