REINNERVATION OF CEREBELLAR PURKINJE-CELLS BY CLIMBING FIBERS SURVIVING A SUBTOTAL LESION OF THE INFERIOR OLIVE IN THE ADULT-RAT .2. SYNAPTIC ORGANIZATION ON REINNERVATED PURKINJE-CELLS
REINNERVATION OF CEREBELLAR PURKINJE-CELLS BY CLIMBING FIBERS SURVIVING A SUBTOTAL LESION OF THE INFERIOR OLIVE IN THE ADULT-RAT .2. SYNAPTIC ORGANIZATION ON REINNERVATED PURKINJE-CELLS
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DOI：
10.1002/cne.903080404
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发表时间：
1991-06-22
影响因子：
2.5
通讯作者：
STRATA, P
中科院分区：
文献类型：
--
作者：
ROSSI, F;VANDERWANT, JJL;STRATA, P
小脑浦肯野细胞的一个显著特征是其兴奋性传入在树突树上的高度有序分布。攀缘纤维只在近端树突上形成突触，而平行纤维则与远端分支（即所谓的多刺小枝）形成突触。这种输入组织随着攀援纤维的去除而丧失。这种去神经导致在近端树突上形成大量新的棘，并且这些棘与发芽的平行纤维接触，从而扩展它们的神经支配域。我们以前已经表明，爬行纤维幸存的次全病变的下橄榄芽和再神经支配邻近的浦肯野细胞。在目前的超微结构研究中，我们已经调查的特点，蒲肯野细胞重新支配发芽攀援纤维。目的是检查新形成的突触的精细形态，并确定浦肯野细胞形态和传入组织的改变是否被这种再神经支配所逆转。存活的攀援纤维用顺行示踪剂Phaseolus vulgaris leucoagglutinin（PHA-L）标记，并通过金取代银过氧化物酶技术进行电化学可视化。成年大鼠下橄榄体3-乙酰吡啶损伤后2个月和6个月。在光学显微镜下观察到萌发的攀援纤维和新形成的树枝状结构，分离并连续切片进行电镜分析。标记的属于新形成的终丛的终扣表现出攀援纤维终末的典型形态特征，即，大量的圆形突触囊泡和少量的小线粒体。最常见的是，它们在从近端浦肯野细胞树突突出的棘上形成不对称的突触。然而，在某些情况下，突触后元件由细长的棘或显示非典型形态的棘组成。一些标记的终扣也在与perikarya的再神经支配的浦肯野细胞，无论是阐明与棘或突触直接在光滑的躯体surfaces.The近端树突失神经浦肯野细胞的特点是大量的棘，这是经常突触后平行纤维。相比之下，蒲肯野细胞重新支配的发芽攀援纤维一般表现出较低数量的棘在其近端树突，这表明逆转的形态变化。异常的平行纤维输入也减少神经支配的树突或已完全消失。然而，一些再神经支配的浦肯野细胞的持久性的一些平行的纤维突触的近端树突。这些结果表明，橄榄小脑轴突的出芽导致浦肯野细胞树突上新的接触的形成，这些接触在形态和位置上与正常的攀爬纤维输入几乎相同。此外，这种侧支神经再支配基本上逆转了影响失神经浦肯野细胞树突的修改，并恢复正常的传入分布。这表明，影响这些连接的个体发育的相互作用仍然活跃在成年动物的再生现象。
A salient feature of the cerebellar Purkinje cells is the highly ordered distribution of their excitatory afferents on the dendritic tree. Climbing fibres synapse exclusively on the proximal dendrites, whereas parallel fibres articulate with the distal branches, the so-called spiny branchlets. This input organization is lost following the removal of climbing fibres. Such denervation results in the formation of a large number of new spines on the proximal dendrites, and these become contacted by sprouting parallel fibres, which thereby extend their domain of innervation. We have previously shown that the climbing fibres surviving a subtotal lesion of the inferior olive sprout and reinnervate neighbouring Purkinje cells. In the present ultrastructural study, we have investigated the features of Purkinje cells reinnervated by sprouting climbing fibres. The objectives were to examine the fine morphology of the newly formed synapses and to determine whether the modifications of Purkinje cell morphology and afferent organization are reversed by this reinnervation.Surviving climbing fibres were labelled by the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L) and immunohistochemically visualized by means of the gold-substituted silver peroxidase technique, 2 and 6 months after 3-acetylpyridine lesions of the inferior olive in adult rats. Sprouting climbing fibres and newly formed arborizations were identified in the light microscope, isolated, and cut in serial ultrathin sections for electron microscopic analysis.The labelled boutons belonging to newly formed terminal plexuses exhibited the typical morphological features of climbing fibre terminals, i.e., a high number of round synaptic vesicles and a few small mitochondria. Most frequently they formed asymmetric synapses on stubby thorns protruding from the proximal Purkinje cell dendrites. In some instances, however, the postsynaptic element consisted of long slender spines or spines showing an atypical morphology. A number of labelled boutons was also in contact with the perikarya of reinnervated Purkinje cells, either articulating with spines or synapsing directly on the smooth somatic surface.The proximal dendrites of denervated Purkinje cells were characterized by large numbers of spines, which were frequently postsynaptic to parallel fibres. By contrast, Purkinje cells reinnervated by the sprouting climbing fibres generally showed a lower number of spines on their proximal dendrites, indicating a reversal of this morphological change. The aberrant parallel fibre input was also decreased on reinnervated dendrites or had completely disappeared. Nevertheless, some reinnervated Purkinje cells showed the persistence of some parallel fibre synapses on their proximal dendrites. On occasion, climbing fibre and parallel fibre boutons synapsed on the same spine.These results show that the sprouting of olivocerebellar axons leads to the formation of new contacts on Purkinje cell dendrites, which are almost identical in morphology and location to the normal climbing fibre input. Moreover, this collateral reinnervation substantially reverses the modifications which affect the denervated Purkinje cell dendrites and restores the normal afferent distribution. It is suggested that the interactions which influence the ontogenetic development of these connections are still active during regenerative phenomena in the adult animal.