Activity of cerebellar Purkinje cells during fictitious scratch reflex in the cat

The activity of Purkinje cells (PCs) was recorded in the anterior lobe (the vermis and pars intermedia) and in the paramedian lobule of the cerebellum during the fictitious scratch reflex in thalamic cats immobilized with Flaxedil. In the anterior lobe, the activity of many PCs was rhythmically modulated in relation to the scratch cycle: they generated bursts of impulses separated by periods of silence. Different PCs were active in different phases of the scratch cycle. In many cases the discharge modulation was irregular: the burst duration and the discharge rate in the burst varied considerably in subsequent cycles. The rhythmical activity of PCs was determined by modulation of the frequency of 'simple spikes' reflecting the mossy fiber input. Generation of 'complex spikes' reflecting the climbing fiber input in most PCs was not related with the scratch rhythm. In the paramedian lobule, rhythmical modulation of PCs was practically absent. Rhythmical modulation of PCs in immobilized cats is determined by signals coming from the central spinal mechanism of scratching via the ventral spinocerebellar tract (VSCT) and the spinoreticulocerebellar pathway (SRCP). Results of separate transections of these pathways demonstrated that the VSCT plays the crucial role in modulating the PCs.     

Three-dimensional orientation of the eye rotation axis during the Purkinje sensation

The otolith-semicircular canal interaction during postrotatory nystagmus was studied in six normal human subjects by applying fast, short-lasting, passive head and body tilts (90° in the roll of pitch plane) 2 s after sudden stop from a constant velocity rotation (100°/s) about the earth-vertical axis in yaw. Eye movements were measured with 3-D magnetic search coils. Following the head tilt, activity in the semicircular canal primary afferents continues to reflect the postrotatory angular velocity vector in head-centered coordinates, whereas otolith primary afferents signal a different orientation of the head relative to gravity. Pitch (roll) tilts away from upright during postrotatory nystagmus after yaw rotation elicited a transient vertical (torsional) VOR. Despite the change in head orientation relative to gravity, postrotatory eye velocity decayed closely along the axis of semicircular canal stimulation (horizontal in head coordinates). These results suggest that postrotary nystagmus is largely organized in head-centered rather than gravity-centered coordinates in humans as suggested by the Purkinje-sensation.     

Behavior and physiology of the macaque vestibulo-ocular reflex response to sudden off-axis rotation: Computing eye translation

The vestibulo-ocular reflex (VOR) has historically been considered a computationally simple reflex: to stabilize images on the retina against imposed head rotation, the eyes must be counterrotated by an equal amount in the opposite direction. During almost any head rotation, however, the eyes are also translated. We show that the VOR compensates for 90% of this translation, and suggest a computational scheme by which this is done, based on a temporal dissection of the VOR response to sudden head rotation. An initial response that corrects only for imposed rotation is refined by a series of three temporally delayed corrections of increasing complexity. The first correction takes only head rotation and viewing distance into account; the second, head rotation, viewing distance, and otolith translation; and the third, head rotation, viewing distance, otolith translation, and translation of the eyes relative to the otoliths. Responses of type I gaze velocity Purkije (GVP) cells in the cerebellar flocculus and ventral paraflocculus of rhesus monkeys were recorded during sudden head rotation. We show that cell discharge was modulated both by axis location and by viewing distance, suggesting that GVP cells play a role in the VOR response to rotation-induced eye translation.     

The human Purkinje cells

Summary Purkinje cells from five autopsy cases (a premature newborn infant, a G_M1-gangliosidosis, an olivo-ponto-cerebellar atrophy, a multisystem atrophy involving the spinal cord and the brain stem, and a woman of 82 years) were studied using the Golgi impregnation technique. The results were the following: (1) the Purkinje cells showed different abnormalities in each case; (2) the dedrite and cell body showed not only involutive/degenerative but also progressive/plastic changes at the same time in some cases; (3) Purkinje cells which appeared normal in routine histological preparations showed, in some cases, abnormalities of the dendrite and cell body; (4) the abnormality common to the five cases was the loss of branchlet-spines and/or spiny branchlets, probably resulting in loss of the granule cell-Purkinje cell connection. It is discussed that the Golgi technique as applied to morbid human material will be an indispensable tool in the future for the analysis of disease processes on cellular and neurobiological bases.     

Spatial organization of proprioception in the cat spinocerebellum. Purkinje cell responses to passive foot rotation

This study examines the spinocerebellar locations of Purkinje cells that responded to passive foot rotations at the ankle joint in anaesthetized cats. Using a novel approach for mapping the locations of recorded cells from several animals onto an unfolded two-dimensional representation of the cortex, we found that cells distributed throughout the anterior-posterior extent of the spinocerebellar cortex, except in the most medial parts corresponding to zones a and b, were responsive to ankle joint rotation. The cell distributions revealed a clustering according to their response amplitudes, which showed evidence for both parasagittal and transverse banding.     

Functional localization in the three floccular zones related to eye movement control in the cat

Anatomically, the cat's cerebellar flocculus can be divided into 3 zones on the basis of differences in their efferent projection sites^13,14. The functional differences of these 3 zones in relation to eye movement control were investigated by observing the eye movements evoked by electric stimulation of each zone of the flocculus in ketamine-anesthetized cats. Stimulation of the flocculus elicited a slow eye movement. The direction of the slow eye movement was mapped. A downward eye movement was evoked by stimulation of the caudal zone. An ipsilateral horizontal eye movement was induced from the middle zone. An upward eye movement was elicited from the rostral zone. When prolonged stimulation was applied to the flocculus, the slow eye movement was followed by nystagmus in the opposite direction. This nystagmus persisted for many seconds after cessation of stimulation (afternystagmus). Nystagmus and afternystagmus could not be elicited in deeply anesthetized cats. Possibilities as to how the stimulation leads to various eye movements are discussed.     

Climbing fibre modification of cerebellar Purkinje cell responses to parallel fibre inputs

Electrical stimulation has been used to activate, separately and independently, the climbing fibre and parallel fibre inputs to Purkinje cells of the cat cerebellum. The effects of climbing fibre impulses on Purkinje cell discharges evoked by parallel fibre stimulation has been examined. It was found that impulses in the climbing fibre could block or reduce, in a graded manner, the Purkinje cell response to parallel fibre inputs. It has previously been shown that climbing fibre inputs do not suppress the antidromic spike response of the Purkinje cell to cerebellar white matter stimulation. This suggests that the climbing fibre impulses modify the Purkinje cell response to parallel fibre inputs by reducing the excitatory action of parallel fibre impulses on the Purkinje cell.     

Zonal organization of the floccular Purkinje cells projecting to the group y of the vestibular nuclear complex and the lateral cerebellar nucleus in cats

Injections of horseradish peroxidase (HRP) were made iontophoretically in the group y of the vestibular nucleus and the lateral cerebellar nucleus (LC) in cats. Topographical distribution of labeled Purkinje cells due to the retrograde axonal transport of HRP was studied in the flocculus. It was found that Purkinje cells in the caudal part of the flocculus project mainly to the ipsilateral group y and sparsely to the ventromedial part of the ipsilateral LC.     

Diversity of cellular physiology and morphology of Purkinje cells in the adult zebrafish cerebellum

This study was designed to explore the functional circuitry of the adult zebrafish cerebellum, focusing on its Purkinje cells and using whole-cell patch recordings and single cell labeling in slice preparations. Following physiological characterizations, the recorded single cells were labeled for morphological identification. It was found that the zebrafish Purkinje cells are surprisingly diverse. Based on their physiology and morphology, they can be classified into at least three subtypes: Type I, a narrow spike cell, which fires only narrow Na⁺ spikes (<3 ms in duration), and has a single primary dendrite with an arbor restricted to the distal molecular layer; Type II, a broad spike cell, which fires broad Ca²⁺ spikes (5–7 ms in duration) and has a primary dendrite with limited branching in the inner molecular layer and then further radiates throughout the molecular layer; and Type III, a very broad spike cell, which fires very broad Ca²⁺ spikes (≥10 ms in duration) and has a dense proximal dendritic arbor that is either restricted to the inner molecular layer (Type IIIa), or radiates throughout the entire molecular layer (Type IIIb). The graded paired-pulse facilitation of these Purkinje cells’ responses to parallel fiber activations and the all-or-none, paired-pulse depression of climbing fiber activation are largely similar to those reported for mammals. The labeled axon terminals of these Purkinje cells end locally, as reported for larval zebrafish. The present study provides evidence that the corresponding functional circuitry and information processing differ from what has been well-established in the mammalian cerebellum.     

Effects of chronic ibogaine treatment on cerebellar Purkinje cells in the rat

The present investigation assessed the chronic toxicity of ibogaine on cerebellar Purkinje cells in male Fischer 344 rats. A behaviorally active dose of ibogaine (10 mg/kg, i.p.) was administered to a group of six subjects every other day for 60 days while the control group received an equivalent volume of saline (1 ml/kg). Estimates of Purkinje cell number were determined using the optical dissector/fractionator technique. No significant differences in Purkinje cell number were observed between the ibogaine (243764[±32766]) and control groups (230813[±16670]).     

Voltage-dependency of the responses of cerebellar Purkinje cells to excitatory amino acids

The voltage-dependency of the responses of Purkinje cells to excitatory amino acids was examined in rat cerebellar slices, using intrasomatic recordings with the single electrode voltage-clamp. In standard perfusion medium, the depolarizations evoked in these neurones by ionophoretic pulse applications (less than 300 ms) of L-glutamate, L-aspartate and quisqualate in their dendritic fields had underlying inward currents which did not increase or even decreased, as the holding potential was shifted to values more negative than -65 mV. This 'abnormal' voltage-dependency was still present in Mg2+ -free solution but was abolished in the presence of CsCl2 (10 mM) in the perfusion medium. When TTX (5 microM) and CdCl2 (0.1 mM) were further added to the bath in order to block regenerative conductances, thus broadening the range of the clamp voltages to more positive values than -50 mV, the current-voltage relation between -80 and 0 mV for responses to L-glutamate and L-asparate was almost linear. Our results support the view that low doses of both amino acids act on Purkinje cells essentially via the activation of receptors which are not of the N-methyl-D-aspartate type.     

Locomotion elicited by pinna stimulation in the acute precollicular-post- mammillary decerebrate cat

In the acute precollicular-postmammillary decerebrate cat, pinna stimulation was found to elicit four-legged locomotion on the treadmill. The adequate stimuli for eliciting locomotion were of the nature of deep pressure with the fingertips. The receptive field of the pinna were distributed along the edge of the scapha. When the existing postural tonus after decerebration were highly exaggerated or depressed, the same stimulation failed to elicit locomotion.     

Gabab receptor-mediated modulation of glutamate signaling in cerebellar Purkinje cells

Since Purkinje cells are the sole output neurons of the cerebellar cortex, the postsynaptic integration of excitatory and inhibitory synaptic inputs in this cell type is a pivotal step for cerebellar motor information processing. In Purkinje cells, Gi/o protein-coupled B-type gamma-aminobutyric acid receptor (GABABR) is expressed at the annuli of the dendritic spines that are innervated by the glutamatergic terminals of parallel fibers. The subcellular localization of GABABR suggests the possibility of postsynaptic interplay between GABABR and glutamate signaling. It has recently been demonstrated that GABABR indeed modulates alpha amino-3-hydroxy-5-methyl-4-isoxalone propionate-type ionotropic glutamate receptor (AMPAR)-mediated and type-1 metabotropic glutamate receptor (mGluR1)-mediated signaling. Interestingly, GABABR exerts modulatory actions not only via the classical Gi/o protein-dependent signaling cascade but also via a Gi/o protein-independent interaction between GABABR and mGluR1. In this review, we compare the physiological nature, underlying mechanisms, and possible functional significance of these modulatory actions of GABABR.     

The existence of substance P in Purkinje cells in cerebellum of the gerbil

We performed this study to identify the characteristics of substance P localization in gerbil cerebellum by immunohistochemistry. Substance P immunoreactivity was present in Purkinje cells of cerebellar cortex but not in other structures. It is suggested that the cerebellar mechanism of gerbil may be different from that of other species.     

Krabbe's disease with giant lamellar bodies in Purkinje cells

An autopsy case of Krabbe's disease in a child aged 6 years 7 months 1s reported. Histologically, globoid cells, loss of myelin, oligodendroglia and axons, and marked gliosis were observed in the white matter. In addition, there was severe neuronal loss in the thalamus, pontine nucleus, dentate nucleus and olivary nuclei. The cerebellar cortex showed extensive loss of granular cells and moderate loss of Purkinje cells. There were numerous eosinophilic inclusion bodies, ranging from 2 to 15 m in diameter, in the dendrites of Purkinje cells. The ultrastructural findings for the inclusion bodies were consistent with those of giant lamellar bodies. In addition, smaller lamellar bodies were frequently observed in the perikarya and dendrites. Although loss of granular cells was more prominent in the hemispheres than in the vermis, the inclusion bodies were observed in hemispheres but were infrequently observed in the vermis. They were found in degenerated Purkinje cells which had lost afferent fibers. It is considered that these giant lamellar body inclusions are an unusual type of degenerative structure specific to Purkinje cells.     

Fate of grafted embryonic Purkinje cells in the cerebellum of the adult "Purkinje cell degeneration" mutant mouse. I. Development of reciprocal graft-host interactions

In this paper, we have morphologically studied the developmental events underlying the neuronal replacement, 3-21 days after grafting. Despite their abnormal environment, Purkinje cell progenitors proceed with their proliferation in the grafted neuroepithelium, with a time window similar to that characterizing proliferation of this neuronal class in control mouse embryos. Only postmitotic Purkinje cells leave the grafts and migrate to the host molecular layer following stereotyped pathways. These neurons invade the host molecular layer, either through a tangential migration under the pial basal lamina from the graft/host interface or breaking locally the latter, and passing directly from the lateral swellings of the graft lying on the surface of the host folia. Whatever the pathway for host invasion, the migrating Purkinje cells penetrate radially and/or obliquely into the host molecular layer until their inward-oriented processes attain the molecular/granular layer interface, which occurs about 7 days after grafting. At the end of their migration, the grafted Purkinje cells with bipolar shapes and long and smooth processes begin to build up their ultimate dendritic trees. This dendritogenesis proceeds with constructive and regressive processes, passing through the same three developmental phases described by Ramón y Cajal (Trab. Lab. Invest. Biol. Univ. Madrid 24:215-251, 1926) for control Purkinje cells (phase of the fusiform cell, phase of the stellate cell with disoriented dendrons, and phase of orientation and flattening of the dendrites). In the grafted cerebella, the duration of the second and third phases is somewhat shorter than during normal cerebellar ontogenesis. Synaptogenesis between adult host axons and grafted Purkinje cells starts when the latter attain their second phase of dendritic development. Somatic filopodia emerging from grafted Purkinje cells begin, 10-11 days after grafting, to be synaptically contacted by axonal sprouts of the host climbing fibers resulting, 2 days later, in the formation of pericellular nests. Synaptogenesis between slender dendritic spines and host parallel fibers, together with that of axon terminals from host molecular layer interneurons and the smooth surface of the grafted Purkinje cell somata, begin earlier than in control mouse development, being almost simultaneous with climbing fiber/Purkinje cell synaptogenesis.(ABSTRACT TRUNCATED AT 400 WORDS)     

Maintenance of immunocytologically identified Purkinje cells from mouse cerebellum in monolayer culture

Purkinje cells were identified in monolayer cultures obtained from trypsin-dissociated cerebella of embryonic and early postnatal mice by the Purkinje cell-specific monoclonal antibodies PC1, PC2, PC3 and UCHT1. These cells also expressed the neuronal marker L1 antigen but not the glial markers, glial fibrillary acidic protein or 04 antigen. They also expressed tetanus toxin receptors, PC4, M1 and Thy-1 antigens. Survival of Purkinje cells was best: (a) when cerebella were taken from mice not older than one day of age: (b) when cells were seeded at higher plating densities; and (c) cultured in chemically defined medium which facilitates the survival of neurons. No Purkinje cells could be detected in cultures from mice older than 6 days. PC1 antigen expression developed in vitro on the same time scale as in vivo, i.e. it was first detectable at the equivalent of postnatal days 3–4. At this stage cell bodies had a size of 13–14 μm in diameter and few processes. Dendrite-like arborizations, with more than one primary dendrite, extension of usually only one thin and long (0.5–1.6 mm) axon-like process and collaterals directed preferentially towards other Purkinje cells, developed with time in culture until the final form was reached by the equivalent of approximately day 16. Cell body size was 18–19 μm in diameter at this stage. Cell shapes were reminiscent of those described in certain cerebellar mouse mutants and in experimentally produced agranular cerebella. Many ultrastructural features of these cells correlated with those described for the in vivo counterpart. However, there was a lack of spiny branchlets and abnormally long persisting somatic spines. Synaptic contacts of the ‘en passant’ type could be seen at the Purkinje cell soma. Gray type I synapses were seen on Purkinje cell dendrites and spines.     

Quantitative study of granule and Purkinje cells in the cerebellar cortex of the rat

The numerical densities of granule and Purkinje cells in the cerebellar cortex of the rat were determined by stereological methods. The density of Purkinje cells in our fixed material was 1,018 +/- 39 per mm2 (mean +/- s.e.m.) of Purkinje cell layer and that of granule cells 1.92 +/- 0.03 x 10(6) per microliter of granular layer. The total area of Purkinje cell layer was 332 mm2 and the volume of granular layer was 48 microliters. The rat cerebellum therefore contains 3.38 x 10(5) Purkinje cells and 9.2 x 10(7) granule cells, from which there are 274 granule cells for each Purkinje cell. The density of granule cells and the density of parallel fibers in the molecular layer observed in a companion study indicate that the average length of a parallel fiber is around 5 mm.     

Purkinje cells express neuronal nitric oxide synthase after methylmercury administration

To study the effects of chemical injury on the cerebella nitric oxide synthase (NOS), we administered methylmercury chloride subcutaneously to mice, 10 mg/kg/day for 9 days. In the methylmercury-treated cerebellum, Purkinje cells were positive both for NADPH-diaphorase and for neuronal NOS. Calcium-dependent NOS activity was increased to 160% of the controls. The present study suggests the ability of Purkinje cells to produce NO through the expression of neuronal NOS.