Degenerative Change of Cerebellar Purkinje Cells by Harmaline Treatment / 체질인류학회지

The indole alkaloid harmaline has been to cause tremor and ataxia, and produce cerebellar neurotoxicity in rat. Degeneration of Purkinje cell alligned in narrow parasagittal bands result from excitation of inferior olivary nucleus in harmaline-treated rats. The objective of this study was to investigate the hypothesis that excitation of climbing fiberinduced by harmaline mediates Purkinje cell injury or degeneration. For this purpose, the inferior olive of rats was chemically ablated by using 3-acetyl pyridine, a neurotoxic chemical, and cerebellar damage followed by administration of harmaline was analyzed using immunohistochemical markers for neurons, glial cells. The results demonstrated that a subset of Purkinje cell in the vermis and paravermis degenerated after harmaline treatment, but harmaline produced little or no Purkinje cell degeneration after inferior olivary ablation. These results suggested that harmalineinduced activation of inferior olivary neurons may lead to release of glutamate from climbing fiber synaptic terminal distributed over the Purkinje cells, and may lead to cytotoxic degeneration of Purkinje cells.

Responses of Inferior Olive Neurons to Stimulation of Semicircular Canals

In spite of abundant anatomical evidences for the fiber connection between vestibular nuclei and inferior olivary (IO) complex, the transmission of vestibular information through the vestibulo- olivo-cerebellar climbing fiber pathway has not been physiologically established. The aims of the present study were to investigate whether there are IO neurons specifically responding to horizontal rotation and also in which subregions of IO complex these vestibularly-activated neurons are located. The extracellular recording was made in 68 IO neurons and responses of 46 vestibularly-activated cells were analyzed. Most of the vestibularly-activated IO neurons responded to signals of vertical rotation (roll), while a small number (13/46) of recorded cells were activated by horizontal canal signal (yaw). Regardless of yaw-sensitive or roll-sensitive, vestibular IO neurons were excited, when the animal was rotated to the side contralateral to the recording side. The gain and excitation phase were very similar to otolithic or vertical-canal responses. Histologic identification of recording sites showed that most of vestibular IO neurons were located in beta subnucleus. Electrical stimulation of a HSC evoked an inhibitory effect on the excitability of the ipsilateral IO neurons. These results suggest that IO neurons mainly in the beta subnucleus receive vestibular signals from semicircular canals and otolithic organs, encode them, and transmit vestibular information to the cerebellum.

Immunohistochemical Study of Insulin-Like Growth Factor-I (IGF-I) in the Olivocerebellar System of Developing and Adult Rats / 대한해부학회지

The developmental topography of olivocerebellar projection is not fully understood. Insulin-like growth factor-I (IGF-I) plays important roles in neural development. This study examined to observe IGF-I-like immunoreactivity (IGF-I IR) in the cerebellum and inferior olive of postnatal developing and adult rats. IGF-I immunoreactive Purkinje cells exhibited spatially and temporally regulated distribution which correlates with climbing fiber development. At birth a few IGF-I immunoreactive Purkinje cells were stained weakly only in the ventral vermis. By P7, all Purkinje cells of the vermis and hemispheres were positively labelled. A subpopulation of Purkinje cells lost IGF-I IR, and IGF-I IR Purkinje cells were divided into discrete population arranged in sagittal strips which were separated by non-reactive Purkinje cells. In the inferior olive, neurons showed IGF-I IR between P0 and P7. By P10 the inferior olive neurons were all negative for IGF-IR and this was mantained to adulthood. The IGF-I IR for Purkinje cell and inferior olive coincides with climbing fiber development and thus the results of this study support the hypothesis that IGF-I is specially involved in the refinement of olivocerebellar topography during synaptogenesis.