Intracellular recordings of oscillatory firing (bursting activity) were obtained from Purkinje cells (PCs) in rat cerebellar slices. Apamin inhibited post-burst hyperpolarizations (PBHs) progressively and finally terminated oscillatory firing activity of PCs. Apamin did not affect the amplitude or duration of the after-hyperpolarization (AHP) between spikes within the burst. In the voltage clamp mode, apamin shifted the whole-cell, quasi-steady state I/V relationship in an inward direction and abolished the zero slope resistance (ZSR) region by blocking outward current. Nickel (Ni2+) terminated oscillatory activity and also abolished the ZSR region. However, Ni2+ did not have progressive blocking action on the post-burst hyperpolarization before it blocked oscillatory activity. Ni2+ blocked an inward current at potentials positive to approximately -65 mV, which was responsible for the ZSR region and outward current at more negative potentials. These data indicated that oscillatory activity of PCs is sustained by a balance between a slow Ni2+ -sensitive inward current and an apamin-sensitive outward current in the region of ZSR of the whole-cell I/V curve.
Animals ; Apamin* ; Fires ; Nickel* ; Purkinje Cells* ; Rats

The purpose of this study is to identify the differences of zebrin II expression between ataxic pogo and normal Balb/C mouse cerebellum. Zebrin II is expressed by subsets of Purkinje cells that form an array of parasagittal bands that extend rostrocaudally throughout the cerebellar cortex, separated by similar bands of Purkinje cells that do not express zebrin II. Zebrin II immunoreactivity was localized in the perikarya of Purkinje cells, and the dendrites. Distribution of zebrin II-immunoreactive Purkinje cells were very similar pattern in pogo and Balb/C mouse cerebellum. But, in the lobule III, distribution of zebrin II expression was different between pogo and Balb/C mouse cerebellum. In lobule III of Balb/c mouse cerebellum, 10~15 zebrin II-immunoreactive Purkinje cells were observed and clustered to form a parasagittal bands. On the other hand, zebrin II expressions of lobule III in pogo mouse cerebellum showed a little different patterns. In lobule III of pogo mouse cerebellum, three bilateral zebrin II immunoreactive parasagittal band were observed. P1 band was almost same with lobule III of Balb/C mouse cerebellum. But, P2 bands were composed of 50~60 Purkinje cells which were immunoreactive with zebrin II. These kind of thickening in zebrin II expression of pogo mouse cerebellum may be due to the genetical difference. Furthermore, these results may provide useful information with further ataxic pogo mice cerebellum studies.
Animals ; Cerebellar Cortex ; Cerebellum* ; Dendrites ; Hand ; Immunohistochemistry ; Mice* ; Purkinje Cells

Intracellular recordings in cerebellar slice preparation showed that applications of 4-AP altered the pattern of oscillatory firing activity in Purkinje cells (PCs), especially yielding pronounced changes in action potential shape. 4-AP increased the amplitude and duration of action potential significantly and decreased the spike frequency. After 4-AP application, the duration of bursting was prolonged and the duration of after-burst hyperpolarization was progressively shortened. In all PCs tested, the rhythmicity of oscillatory firing activity was abolished completely at the steady state. These results suggest that 4-AP-sensitive currents determine the shape and frequency of individual Ca(2+)-dependent action potentials as well as maintaining oscillatory firing activity in PCs.
4-Aminopyridine/pharmacology* ; Action Potentials/drug effects* ; Animal ; Calcium/physiology* ; Electrophysiology ; In Vitro ; Oscillometry ; Purkinje Cells/physiology* ; Purkinje Cells/drug effects* ; Rats ; Rats, Sprague-Dawley

We reviewed the anatomical characteristics of the conduction system in the ventricles of human and ungulate hearts and then raised some questions to be answered by clinical and anatomical studies in the future. The ventricular conduction system is a 3-dimensional structure as compared to the 2-dimensional character of the atrial conduction system. The proximal part consisting of the atrioventricular node, the bundle of His and fascicles are groups of conducting cells surrounded by fibrous connective tissue so as to insulate from the underlying myocardium. Their location and morphological characters are well established. The bundle of His is a cord like structure but the left and right fascicles are broad at the proximal and branching at the distal part. The more distal part of fascicles and Purkinje system are linear networks of conducting cells at the immediate subendocardium but the intra-mural network is detected at the inner half of the ventricular wall. The papillary muscle also harbors Purkinje system not in the deeper part. It is hard to recognize histologically in human hearts but conducting cells as well as Purkinje cells are easily recognized in ungulate hearts. Further observation on human and ungulate hearts with myocardial infarct, we could find preserved Purkinje system at the subendocardium in contrast to the damaged system at the deeper myocardium. Further studies are necessary on the anatomical characteristics of this peripheral conduction system so as to correlate the clinical data on hearts with ventricular arrhythmias.
Arrhythmias, Cardiac ; Atrioventricular Node ; Bundle of His ; Connective Tissue ; Heart ; Heart Conduction System ; Humans ; Myocardial Infarction ; Myocardium ; Papillary Muscles ; Purkinje Cells ; Purkinje Fibers ; Tachycardia, Ventricular

This study examined the acute effects of ethanol (EtOH) on the firing patterns of Purkinje cells (PCs) using an intracellular recording in slice preparation of rat cerebellum. The experiments were performed in sagittal cerebellar slices (400 microm) of adult Sprague-Dawley rats (80-100g). Ethanol was applied by a bath superfusion with a known concentration expressed as the percentage of solution by volume (v/v) at 0.1, 0.5, 1, 2, and 4%. The result of the Chi-square test illustrated that the firing patterns were altered significantly after EtOH (p=0.007). However, the firing patterns that were altered by EtOH application were not affected by EtOH concentration (p= 0.1296). Among the 54 PCs tested, 30 PCs did not display any spontaneous firing activity and 24 PCs displayed spontaneous spike activity, either spiking in the simple manner (n=14) or cyclicly oscillating (n=10). In the presence of EtOH, 31 PCs were quiet, 22 PCs exhibited simple spiking activity and 1 PC continued to oscillate. Most PCs that displayed spontaneous activity before EtOH application progressively slowed their spike activity after EtOH superfusion. Especially, it was evident that 9 out of 10 oscillating PCs stopped their regular cyclic activity. In addition, 9 out of 14 PCs that displayed simple spike activity ceased to fire after EtOH application. Eleven out of 30 quiet PCs began to fire irregularly after EtOH application and this phenomenon usually occurred with membrane depolarization. EtOH induced spontaneous activity in 36.7% (11/30) of the quiescent PCs. In conclusion, there was differential EtOH sensitivity in the vitro slice preparation. EtOH depressed the endogenously generated spontaneous activity, especially the oscillatory firing activity. In contrast, the silent PCs were excited after EtOH application. Since this differential sensitivity persists in the presence of tetrodotoxin (TTX), it is suggested that this differential sensitivity is peculiar to the PCs.
Animal ; Ethanol/*toxicity ; In Vitro ; Purkinje Cells/*drug effects/physiology ; Rats ; Rats, Sprague-Dawley ; Tetrodotoxin/pharmacology

VEGF and its receptors, flk-1 and flt-1 have been characterized as critical factors in angiogenesis and neurogenesis during development. Here we investigated the expression of VEGF and its receptors in postnatal murine cerebellum in terms of time-dependency and regional distribution. Immunofluorescence staining showed that the expression of VEGF was restricted only to Purkinje cells and was increased in their processes on the postnatal development. Flk-1 was expressed in Purkinje cellular bodies on postnatal day (P) 8, 11, 18. Flt-1 was expressed in Purkinje cells on P8 but gradually disappeared in all of cerebellar layers on the postnatal development. These results suggest that VEGF may contribute to postnatal development of cerebellum via its receptors. And they suggest that changes in the expression of VEGF and its receptors related to the difference in maturation and proliferation of Purkinje cells in the cerebellum.
Cerebellum ; Fluorescent Antibody Technique ; Neurogenesis ; Purkinje Cells ; Vascular Endothelial Growth Factor A

The biological activities of PDGF include stimulation of mitogenesis, chemotaxis, and differentiation. In nervous system, previous studies have shown that PDGF has an important role in the generation of cells of a glial lineage. However, several studies demonstrated that mature and immature neurons could also synthesize PDGF-alphaR. In the present study, to analyze the distributional pattern of PDGF-alphaR during postnatal development of the canine cerebellum, we used immunohistochemistry. We found that neurons of cerebellum, including Purkinje cells and granules cells, showed immunoreactivity to PDGF-alphaR (IRPDGF-alphaR) as early as postnatal day 0. Whereas IRPDGF-alphaR immunoreactivity in the Purkinje cells were maintained at all postnatal ages. Our data support that PDGF may have the important roles during development and survival of neurons.
Animals ; Cerebellum* ; Chemotaxis ; Dogs ; Immunohistochemistry ; Nervous System ; Neurons ; Platelet-Derived Growth Factor* ; Purkinje Cells

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.
Adult* ; Animals ; Cerebellum ; Humans ; Insulin-Like Growth Factor I ; Neurons ; Olea ; Parturition ; Purkinje Cells ; Rats*

Tumor endothelial marker 7 (TEM7) is a putative transmembrane protein that is highly expressed in the tumor endothelium and cerebellar neurons. In the present study, the expression profile of TEM7 mRNA and its putative ligand in the developing cerebellum of the rat was investigated using in situ hybridization and ligand binding assay. The secreted recombinant ectodomain of TEM7 was employed to label the expression of putative ligand of TEM7 in the cerebellum. The expression of a putative ligand of TEM7 demonstrated by using TEM7 ectodomain was found in the molecular layer of the cerebellum, where the dendritic trees of Purkinje cells are present. A developmental study has shown that TEM7 mRNA expression in the Purkinje neurons was increased with age during postnatal development, whereas the putative ligand labeling in the molecular layer was observed throughout the developmental period. These findings indicate that TEM7-ligand interaction plays a role in the differentiation of Purkinje cells during postnatal development.
Animals ; Cerebellum* ; Endothelium ; In Situ Hybridization ; Neurons ; Purkinje Cells ; Rats* ; RNA, Messenger*

Although cerebellar Purkinje cells display spontaneous electrical activity in vivo and in slice experiments, the mechanism of the spontaneous activity generation has not been clearly understood. The aim of this study was to investigate whether cerebellar Purkinje cells of postnatal rats generate spontaneous electrical activity without synaptic inputs. Dissociated cerebellar Purkinje cells were used for reducing synaptic inputs in the present study. Cerebellar Purkinje cells with dendrites were dissociated from postnatal rats using enzymatic treatment followed by mechanical trituration. Spontaneous electrical activities were recorded from dissociated cells without any stimulus using whole-cell patch clamp configuration. Two types, spontaneously firing or quiescent, of dissociated Purkinje cells were observed in postnatal rats. Both types of cells were identified as Purkinje cells using immunocytochemical staining technique with anti-calbindin after recording. Spontaneously active cells displayed two patterns of firing, repetitive and burst firings. Two thirds of dissociated Purkinje cells displayed repetitive firing and the rest of them did burst firing under same recording condition. Repetitive firing activities were maintained even after further isolation using either physical or pharmacological techniques. Neither high magnesium solution nor excitatory synaptic blockers, AP-5 and DNQX, block the spontaneous activity. These results demonstrate that spontaneous electrical activity of isolated cerebellar Purkinje cells in postnatal rats is generated by intrinsic membrane properties rather than synaptic inputs.
Animals ; Cell Separation ; Dendrites ; Fires ; Magnesium ; Membranes ; Neurons* ; Purkinje Cells ; Rats*