D'Ascanio P, Lucacchini A, Martini C, Pompeiano O
Arch Ital Biol. 1985 Feb;123(1):13-26.
In adult cats, local injection of kainic acid (KA) in the inferior olive (IO) of one side, from which the crossed olivocerebellar projection originates, produced asymmetric postural and motor deficits, attributed to selective damage of the olivary neurons. Since aspartate is one of the putative transmitters of the olivocerebellar fibers, experiments were performed to find out whether 6-8 days after injection of KA within the IO of one side produced changes in aspartate receptors binding in different zones of the cerebellar cortex. In particular, binding in the contralateral zones of the cerebellar cortex was referred to proteins contained in membrane suspensions and compared with the control values obtained in the same experiments from the ipsilateral zones. Binding of L-[3H] aspartate decreased on the average to 53.4% of the control value in the medial zone and to 86.1% of the control value in the intermediate and lateral zones of the cerebellar cortex. This reduction varied in different experiments according to the side of the injection, in agreement with the well known pattern of regional distribution of the olivocerebellar projection within the cerebellar cortex. These findings favour aspartate as the putative neurotransmitter of the climbing fibers. The demonstration that binding of aspartate decreased in the cerebellar cortex of one side, 6-8 days after injection of KA in the corresponding IO, indicates that plastic events occur at this level following destruction of the olivocerebellar pathway. In particular, the reduced binding can be attributed either to a decrease in number of the postsynaptic receptor sites for aspartate or to a decreased affinity of this amino acid for the corresponding receptors. These findings, however, do not exclude that an hypersensitivity by denervation may occur at the level of individual Purkinje cells when they are deprived of the climbing fibers input. In order to answer this question further experiments are required to find out how the binding for aspartate is modified at increasing time intervals after the olivary lesion.
在成年猫中，向一侧下橄榄核（IO）局部注射海藻酸（KA），交叉橄榄小脑投射由此发出，会产生不对称的姿势和运动缺陷，这归因于橄榄核神经元的选择性损伤。由于天冬氨酸是橄榄小脑纤维的假定递质之一，因此进行了实验，以探究在一侧IO注射KA 6 - 8天后，小脑皮质不同区域的天冬氨酸受体结合是否发生变化。特别是，将小脑皮质对侧区域的结合情况与膜悬浮液中的蛋白质进行比较，并与同一实验中同侧区域获得的对照值进行比较。小脑皮质内侧区域L - [³H]天冬氨酸的结合平均降至对照值的53.4%，中间和外侧区域降至对照值的86.1%。根据注射侧的不同，这种减少在不同实验中有所变化，这与橄榄小脑投射在小脑皮质内的区域分布模式一致。这些发现支持天冬氨酸作为攀缘纤维的假定神经递质。在相应的IO注射KA 6 - 8天后，一侧小脑皮质中天冬氨酸结合减少的证明表明，在橄榄小脑通路破坏后，该水平发生了可塑性变化。特别是，结合减少可能归因于天冬氨酸突触后受体位点数量的减少，或者该氨基酸与相应受体亲和力的降低。然而，这些发现并不排除当单个浦肯野细胞被剥夺攀缘纤维输入时，可能会在去神经水平发生超敏反应。为了回答这个问题，需要进一步的实验来探究在橄榄核损伤后不同时间间隔内天冬氨酸结合是如何改变的。
