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PubMed1997

Retrograde and anterograde labeling of cerebellar afferent projection by the injection of recombinant adenoviral vectors into the mouse cerebellar cortex.

Adenoviral vectors have recently been recognized as highly efficient systems for gene delivery into various tissues. We show that a reporter gene introduced into nerve terminals via an adenovirus can be used to label cell bodies retrogradely and then label the axons and nerve terminals of the infected neurons anterogradely in vivo. We injected a replication-defective recombinant adenovirus carrying the E. coli beta-galactosidase gene (lacZ) into the cerebellar cortex of the adult mouse. The first evidence of retrograde labeling was obtained at 2 days after the infection when neurons in the pontine nuclei and the reticulotegmental nucleus of the pons weakly expressed beta-galactosidase, and at 3 days post-infection when neurons in all precerebellar nuclei, known to project to the cerebellar cortex, were strongly stained with X-gal in a Golgi-like manner. Anterograde transport of lacZ gene products was recognized at 3 days post-infection; beta-galactosidase-positive axons arose from somata or dendrites of retrogradely labeled neurons, passed through the middle or inferior cerebellar peduncles, and entered the cerebellum. Anterogradely labeled mossy terminals were recognized on the injection side at 8 days post-infection, and on the contralateral side at 14 days post-infection. Beta-galactosidase expression persisted for up to two months, with a decrease in the total number of labeled cells over time. We could not find any signs of anterograde or retrograde transsynaptic labeling in the nuclei synaptically linked to the cerebellar cortex at any time point after injection up to 58 days post-infection.

Adenoviridae↗

PubMed1996

Functional parasagittal compartments in the rat cerebellar cortex: an in vivo optical imaging study using neutral red.

1. The spatial patterns of activation in the rat cerebellar cortex evoked by peripheral stimulation were studied in vivo using optical imaging techniques. 2. Crus I and Crus II were stained with the pH sensitive dye, neutral red. Electrical stimulation of the vibrissae area of the ipsilateral face evoked optical responses consisting of parasagittal bands. The bands were 100-300 microns in width, elongated in the anterior-posterior direction, commonly extended across at least two folia, and varied in number from 1 to 7. 3. The optical responses were dependent on activation of postsynaptic elements since they were decreased substantially by the non-N-methyl-D-aspartate antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione. The optical bands were shown to correspond anatomically with the parasagittal compartments revealed by immunostaining with anti-zebrin II. 4. The present study demonstrates that functional parasagittal compartments exist in the rat cerebellar cortex and suggests that zebrin-positive Purkinje cell subgroups are anatomically related to this functional organization.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed2005

Involvement of kv1 potassium channels in spreading acidification and depression in the cerebellar cortex.

Spreading acidification and depression (SAD) is a form of propagated activity in the cerebellar cortex characterized by acidification and a transient depression in excitability. This study investigated the role of Kv1 potassium channels in SAD using neutral red, flavoprotein autofluorescence, and voltage-sensitive dye optical imaging in the mouse cerebellar cortex, in vivo. The probability of evoking SAD was greatly increased by blocking Kv1.1 as well as Kv1.2 potassium channels by their specific blockers dendrotoxin K (DTX-K) and tityustoxin (TsTX), respectively. DTX-K not only greatly lowered the threshold for evoking SAD but also resulted in multiple cycles of spread and spontaneous SAD. The occurrence of spontaneous SAD originating from spontaneous parallel fiber-like beams of activity suggests that blocking Kv1 channels increased parallel fiber excitability. This was confirmed by the generation of parallel fiber-like beams with the microinjection of glutamate into the upper molecular layer in the presence of DTX-K. The dramatic effects of DTX-K suggest a possible connection between SAD and episodic ataxia type 1 (EA1), a Kv1.1 potassium channelopathy. The threshold for evoking SAD was significantly lowered in the Kv1.1 heterozygous knockout mouse compared with wild-type littermates. Carbamazepine and acetazolamide, both effective in the treatment of EA1, significantly decreased the likelihood of evoking SAD. Blocking GABAergic neurotransmission did not alter the effectiveness of DTX-K. The cyclin D2 null mouse, which lacks cerebellar stellate cells, also exhibited SAD. Therefore blocking Kv1 potassium channels establishes the conditions needed to generate SAD. Furthermore, the results are consistent with the hypothesis that SAD may underlie the transient attacks of ataxia characterizing EA1.

Acetazolamide↗

PubMed1994

Granular layer collaterals of the unipolar brush cell axon display rosette-like excrescences. A Golgi study in the rat cerebellar cortex.

The unipolar brush cell (UBC) is a medium-sized neuron located in the granular layer of the cerebellar cortex and morphologically characterized by a single dendritic shaft terminated by a brush-like tuft [Mugnaini and Floris, J. Comp. Neurol., in press]. This neuronal class is mostly encountered in the vestibular part of the cerebellum, although also present in the rest of the vermal folia. The UBC axon, as seen in Golgi impregnated material, has a tortuous course throughout the granular layer and gives off number of collaterals of variable diameter. Some of the axon collaterals enter the white matter only for a short distance, after which they ascend into the granular layer. Astonishingly, some of the thick granular collaterals of these axons display characteristic expansions resembling the rosette excrescences seen on mossy fibers. In our series these rosettes are mostly of the simple type [Palay, S. and Chan-Palay, V., Cerebellar Cortex. Cytology and Organization, Springer, Berlin, 1974], i.e. short swellings with simple globular contours. The exact projection targets and functional effect of the UBC axon and granular rosettes have still to be demonstrated.

Animals↗

PubMedDate not supplied

GABA immunoreactivity in the human cerebellar cortex: a light and electron microscopical study.

The distribution of gamma-aminobutyric acid (GABA) in surgical samples of human cerebellar cortex was studied by light and electron microscope immunocytochemistry using a polyclonal antibody generated in rabbit against GABA coupled to bovine serum albumin with glutaraldehyde. Observations by light microscopy revealed immunostained neuronal bodies and processes as well as axon terminals in all layers of the cerebellar cortex. Perikarya of stellate, basket and Golgi neurons showed evident GABA immunoreactivity. In contrast, perikarya of Purkinje neurons appeared to be negative or weakly positive. Immunoreactive tracts of longitudinally- or obliquely-sectioned neuronal processes and punctate elements, corresponding to axon terminals or cross-sectioned neuronal processes, showed a layer-specific pattern of distribution and were seen on the surface of neuronal bodies, in the neuropil and at microvessel walls. Electron microscope observations mainly focussed on the analysis of GABA-labelled axon terminals and of their relationships with neurons and microvessels. GABA-labelled terminals contained gold particles associated with pleomorphic vesicles and mitochondria and established symmetric synapses with neuronal bodies and dendrites in all cortex layers. GABA-labelled terminals associated with capillaries were seen to contact the perivascular glial processes, basal lamina and endothelial cells and to establish synapses with subendothelial unlabelled axons.

Aged↗

PubMed1992

The degeneration of the excitatory climbing fibers enhances [3H]MK-801 and [3H]CGP 39653 binding sites in the rat cerebellar cortex.

The effect of a single injection of 3-acetylpyridine (3-AP), which led to a degeneration of the excitatory cerebellar climbing fibers, was studied on the binding of [3H]MK-801, a non-competitive NMDA antagonist, in the rat cerebellar cortex. The same treatment increased also the binding of [3H]CGP 39653, a new NMDA competitive antagonist. Saturation isotherms showed a significant increase of the maximal number of binding sites (Bmax) for [3H]CGP 39653 and [3H]MK-801 (+48 and 36% respectively) with no change in the affinity 4-9 days after the administration of 3-AP. Our data demonstrate that in the cerebellar cortex both NMDA recognition site labelled by [3H]CGP 39653 and its modulatory site labelled by [3H]MK-801 may undergo plastic changes when the glutamatergic receptors and transmission are denervated.

2-Amino-5-phosphonovalerate↗

PubMed2005

MRI-based surface-assisted parcellation of human cerebellar cortex: an anatomically specified method with estimate of reliability.

We revisit here a surface assisted parcellation (SAP) system of the human cerebellar cortex originally described in Makris, N., Hodge, S.M., Haselgrove, C., Kennedy, D.N., Dale, A., Fischl, B., Rosen, B.R., Harris, G., Caviness, V.S., Jr., Schmahmann, J.D., 2003. Human cerebellum: surface-assisted cortical parcellation and volumetry with magnetic resonance imaging. J Cogn Neurosci 15, 584-599. This system preserves the topographic and morphologic uniqueness of the individual cerebellum and allows for volumetric analysis and representation of multimodal structural and functional data on the cerebellar cortex. This methodology integrates features of automated routines of the program FreeSurfer as well as semi-automated and manual procedures of the program Cardviews to create 64 cerebellar parcellation units based on fissure information and anatomical landmarks of the cerebellar surface. Using this technique, we undertook the parcellation of ten cerebella by two independent raters. The reliability of the resulting parcellation units (64 total) was high, with an average Intraclass Correlation Coefficient (ICC) of 0.724 in the vermis and 0.853 in the hemispheres. Clusters of parcellation units were then created, based on lobar and connectivity data and functional hypotheses. These 36 clusters, when treated as anatomical units, had an average ICC of 0.933. Whereas the individual units provide a high level of detail and anatomical specificity, the clusters add flexibility to the analysis by providing higher reliability.

Algorithms↗

PubMed1991

Topographical organization in the origin of serotoninergic projections to different regions of the cat cerebellar cortex.

The distribution of serotonin immunoreactivity in the cat cerebellum was studied by using the indirect antibody peroxidase-antiperoxidase (PAP) technique. Furthermore, the origin of these chemically defined afferents was determined by combining the retrograde transport of horseradish peroxidase (HRP) with the PAP technique. In the cerebellar cortex, serotonin immunoreactivity is present in a plexus of beaded fibers that is confined almost exclusively to the granule and Purkinje cell layers; a few fibers are present in the molecular layer. Serotoninergic axons and varicosities have a dense and uniform distribution throughout all lobules of the cerebellum with the exception of lobule X where the fiber density is sparse. Serotonin cell bodies were not found within the cerebellar cortex. However, following pretreatment with pargyline and L-tryptophan, serotonin positive cell bodies were found in all deep cerebellar nuclei as well as the raphe and reticular nuclei in the brainstem. The present study demonstrates that the serotoninergic projection to the cat's cerebellum has some degree of topographical organization. Serotoninergic fibers in the anterior vermis (lobules I-V) were shown to arise from neurons located within the paramedian reticular nucleus, the lateral reticular nucleus, and the lateral tegmental field. Injections of HRP into either the posterior vermis (lobule VI-IX) or the paramedian lobule, labeled serotoninergic neurons exclusively in the lateral reticular nucleus. Lobus simplex, crus I and crus II (the hemisphere) receive a serotoninergic input from cells located in the lateral tegmental field, the peri-olivary reticular formation and the paramedian reticular nucleus. In no cases were neurons in the raphe double-labeled, although there were cells positive for HRP or serotonin alone. The data indicate that there is a topographical organization in the serotoninergic projection from the caudal brainstem to specific regions of the cat's cerebellar cortex. In addition to climbing and mossy fibers, this projection represents a third major source of cerebellar afferents based on its dense and widespread distribution as well as its morphological and chemical characteristics.

Animals↗

PubMed1990

Immunogold electron microscopic demonstration of glutamate and GABA in normal and deafferented cerebellar cortex: correlation between transmitter content and synaptic vesicle size.

Selective labeling of mossy fiber terminals and parallel fibers was obtained in rat cerebellar cortex by a glutamate antibody produced and characterized by Hepler et al. The high-resolution electron microscopic immunogold demonstration of this amino acid offered the possibility of determining the size and shape of synaptic vesicles in glutamate-positive mossy endings. Mossy terminals that stained with the glutamate antibody formed two distinct populations, one with spherical synaptic vesicles with an average diameter of 34.0 nm (more than 90% of all mossy fiber endings) and one with pleomorphic and smaller synaptic vesicles which had an average diameter of 28.5 nm. We present experimental evidence that the mossy terminals with large round vesicles are of extracerebellar origin, whereas those with small pleomorphic synaptic vesicles are endings of nucleocortical fibers. The presence of two distinct classes of gamma-aminobutyric acid (GABA)-containing axon terminals within cerebellar glomeruli has also been demonstrated; those originating from the cerebellar nuclei contain large (36.2 nm) synaptic vesicles, whereas the majority of GABA-stained axon terminals that are of local (cortical) origin contain small (29.1 nm) synaptic vesicles. It therefore appears that, at least in the case of glutamate and GABA, morphological characterization of the axon terminals based on the size and shape of synaptic vesicles is not a reliable indicator of their functional nature (i.e., whether they are excitatory or inhibitory); convincing evidence for the identity of the transmitter can be obtained only by electron microscopic immunostaining procedures. Our results also suggest the existence of both inhibitory and excitatory feedback from cerebellar nuclei to cerebellar cortex.

Animals↗

PubMed2005

Developmental expression of GABA transporter-1 and 3 during formation of the GABAergic synapses in the mouse cerebellar cortex.

In the brain, gamma-amino butyric acid (GABA), released extrasynaptically and synaptically from GABAergic neurons, plays important roles in morphogenesis, expression of higher functions and so on. In the GABAergic transmission system, plasma membrane GABA transporters (GATs) mediate GABA-uptake from the synaptic cleft in the mature brain and are thought to mediate diacrine of cytosolic GABA in the immature brain. In the present study, we focused on two GATs (GAT-1 and GAT-3) in the mouse cerebellar cortex, which are widely localized in neural and glial cells. Firstly, we examined the localization of GATs in the dendrites and cell bodies of developing GABAergic neurons, where GABA is extrasynaptically distributed, to clarify the GABA-diacrine before synaptogenesis. Secondly, we examined the developmental changes in the localization of GATs to reveal the development of the GABA-uptake system. Neither transporter was detected within the dendrites and cell bodies of GABAergic neurons, including Purkinje, stellate, basket and Golgi cells, in the immature cerebellar cortex. GAT-1 was observed within the Golgi cell axon terminals after postnatal day 5 (P5) and presynaptic axons of stellate and basket cells after P7. GAT-3 was localized within the astrocyte processes, sealing the GABAergic synapses in the Purkinje cell and granular layers after P10. These results indicated that GABA-diacrine did not work in the mouse cerebellar cortex. The onset of GAT-1-expression was prior to that of GAT-3. GAT-1 started to be localized within the GABAergic axon terminals during synapse formation. GAT-3 started to be localized within astrocyte processes when they sealed the synapses.

Age Factors↗

PubMed1985

Fusiform nerve cells of the granular layer in the cerebellar cortex of the baboon.

The granular layer of the cerebellar cortex of the baboon contains a heterogeneous population of large nerve cells. Besides the well known Golgi cells there is a fusiform type of nerve cell which is mostly encountered immediately underneath the Purkinje cell layer. The fusiform nerve cells can be distinguished from Golgi cells not only in Golgi-impregnated material but also in Nissl-stained preparations. The fusiform nerve cells are evenly distributed throughout the superficial portions of the granular layer. The ratio of the Purkinje cells versus fusiform nerve cells is 4:1.

Animals↗

PubMed1992

Embryonic Purkinje Cells Grafted on the Surface of the Cerebellar Cortex Integrate in the Adult Unlesioned Cerebellum.

The presence of an injury or the selective degeneration of specific neuronal populations is commonly assumed to be a necessary prerequisite for the survival and the integration of grafted neurons in the recipient brain. In the present study we have placed solid grafts of cerebellar anlage in the fourth ventricle of adult rats, in close contact with the host cerebellar cortex, to assess the capacity of embryonic Purkinje cells to interact with adult neurons and integrate in the unlesioned cerebellar cortex. Numerous grafted Purkinje cells are indeed able to leave the implant and migrate into the host molecular layer, where they develop adult structural features. In addition, such cells are able to elicit the growth of host climbing fibre sprouts which end in newly formed arborizations impinging upon their dendritic trees. Climbing fibre collateral branches also penetrate the implant to innervate Purkinje cells which have not migrated in the host cerebellum. These results show that embryonic Purkinje cells are able to survive and integrate in an adult unlesioned cerebellar cortex. In addition, adult olivary axons respond to the increased size of the target population by expanding their terminal domain to innervate grafted Purkinje cells.

Journal Article↗

PubMed2002

Tonic and spillover inhibition of granule cells control information flow through cerebellar cortex.

We show that information flow through the adult cerebellar cortex, from the mossy fiber input to the Purkinje cell output, is controlled by furosemide-sensitive, diazepam- and neurosteroid-insensitive GABA(A) receptors on granule cells, which are activated both tonically and by GABA spillover from synaptic release sites. Tonic activation of these receptors contributes a 3-fold larger mean inhibitory conductance than GABA released synaptically by high-frequency stimulation. Tonic and spillover inhibition reduce the fraction of granule cells activated by mossy fiber input, generating an increase of coding sparseness, which is predicted to improve the information storage capacity of the cerebellum.

Action Potentials↗

PubMed1987

[Comparative physiologic study of the responses of cerebellar cortex neurons to stimulation of the vagus nerve].

The cerebellar cortex neuronal responses (of Purkinje cells--PC, and of unidentified neurons UN) to vagus stimulation in anesthetized pigeons, rats and monkeys were actualized as spikes or as complex discharges in PC. Tonic neuronal responses were mainly excitatory. All the PC and the majority of UN were polymodal. Differences in the line: birds--mammals, started with an increase of responsiveness, particularly on account of mossy fibers input. A shortening of neuronal responses latency was observed. In monkeys only, a lengthening of inhibitory pauses and a variability of afterdischarges were found. The significance of cerebellum in interoceptive information processing seems to increase in phylogenesis.

Animals↗

PubMed1978

Electron microscopic analysis of postnatal histogenesis in the cerebellar cortex of staggerer mutant mice.

Postnatal development of the cerebellar cortex has been compared in staggerer mutant and unaffected littermate mice. From postnatal day 3 to about day 21 the external granular layer in staggerer mice is decreased in thickness and area, and the number of postmitotic granule cell neurons is reduced. Those granule cells that are generated seem to differentiate normally, with the remarkable exception that they form only primitive junctions with Purkinje cell dendritic shafts. These specialized junctions are not superseded by the normal parallel fiber:Purkinje spine synapses and disappear by the third week. Purkinje cell somata and dendrites are smaller than normal at all stages examined. The dendrites are not confined to the sagittal plane as in the normal and, unique among mutant or other animals described to date, they exhibit virtually no branchlet spines. All other cortical synaptic relations of granule and Purkinje cells, including climbing fiber:Purkinje spine synapses, appear qualitatively normal. However, by 28 days virtually all staggerer granule cells have degenerated. While the primary genetic defect remains unknown, we postulate that the morphological abnormalities may be attributable to a block in the normal developmental relationship between granule cells and Purkinje cells. The small cell size and failure to form branchlet spines suggest that the Purkinje cell abnormality may be closer to the primary effect of the mutant gene than the more flagrant hypoplasia and degeneration of granule cell neurons.

Animals↗

PubMed2005

Frequency-dependent recruitment of inhibition mediated by stellate cells in the rat cerebellar cortex.

In the cerebellum, dendritic inhibition of Purkinje cells (PCs) is mediated by stellate cells (SCs). These inhibitory interneurons are critically involved in the cerebellar network; they control the timing and firing frequency of PCs, the only output cells of the cerebellar cortex. However, the underlying properties of parallel fiber (PF) to SC excitatory synapses have not been fully determined. To characterize the conditions favoring the recruitment of SCs in the cerebellum, we analyzed evoked and spontaneous excitatory postsynaptic currents (EPSCs) recorded from SCs of rat cerebellar slices. We found that SC EPSCs evoked with single suprathreshold-intensity stimulations were mostly unitary, with a large amplitude and variable latencies, and failed with a high rate. Increasing the frequency of stimulation above 60 Hz significantly reduced failures, whereas mean SC EPSC amplitude was increased by less than 20%. Decreasing failures at PF-SC synapses experimentally enhanced the number of asynchronous SC EPSCs per stimulation but, again, moderately increased the mean SC EPSC amplitude. Finally, brief presynaptic bursts transiently depressed synaptic transmission. This depression resulted from the release of endocannabinoids and might act as a negative-feedback mechanism. Thus, we conclude that SC EPSCs evoked with single suprathreshold-intensity stimulations are mostly unitary and that PF-SC synapse efficacy is highly regulated by the presynaptic temporal pattern of activity and the frequency of afferent inputs. Such synaptic properties may control the responsiveness of SC synapses to the frequency of PF stimulations, which may control the spatial extent and duration of the recruitment of inhibition in the cerebellar cortex.

Animals↗

PubMed1998

Changes in the cerebellar cortex of hairless Rhino-J mice (hr-rh-j).

A mutation in the hr gene is responsible for typical epithelium phenotype in hairless mice. As this gene is expressed at high levels not only in the skin but also in the brain, the aim of the study was to clarify its role in the central nervous system. We have analyzed by morphological and immunocytochemical methods (calbindin D-28k, phosphorylated and 200 kDa neurofilament protein) the cerebellum of a mutated mouse strain, the hairless (hr-rh-j) type carrying the homozygous hr gene rhino mutation. The cerebellar cortex was studied in young (3 months) and adult (9 months) wild type and mutated mice. No major structural change was found in any of the groups and neuronal density or neuronal arrangement were similar in mutated animals to their age-matched controls. Nevertheless there were changes in shape and size of the Purkinje neurons in the old mutated animals respect to their normal littermates, while the molecular and the granule cell layers were apparently invariable. Calbindin (CB) immunohistochemistry revealed a significant decrease in the expression of this protein in the Purkinje cells of the aged mutated mice. Immunohistochemistry for a neurofilament protein (NFP) showed a reduction of staining in all the cerebellar cortex layers in the older animals, which was much more evident in the (hr-rh-j) mutated mice. These results suggest that hr gene is involved in the structural maintenance of the mature cerebellar cortex, rather than in the development. Our findings may also be consistent with an accelerated aging of the central nervous system in rh-rh-j mice.

Aging↗

PubMed1989

Purkinje cell axon collateral distributions reflect the chemical compartmentation of the rat cerebellar cortex.

Monoclonal antibody mabQ113 has been used to study the distribution of Purkinje cell axon collaterals in the rat cerebellar cortex. MabQ113 recognizes a polypeptide antigen, zebrin I, that is confined to a subset of Purkinje cells. Antigenic Purkinje cells are arranged in parasagittal compartments running throughout the cortex. No other cerebellar cells are immunoreactive. Immunoreactive axon collaterals are confined principally to the infraganglionic plexus with only a few extending into the molecular layer. Three probable target cells for the axon collaterals have been identified: Golgi cells, Lugaro cells, and other Purkinje cells. About 90% of immunoreactive axon collaterals in the anterior lobe are located beneath the mabQ113+ Purkinje cell compartment in which they originate but some do invade the neighboring mabQ113- territory. In the anterior lobe vermis, the distribution of invading mabQ113+ collaterals is not symmetrical, such that the probability of an invading collateral from the P2+ compartment is greater at the medial boundary into P1- than at the lateral into P2-. The distribution of immunoreactive collaterals is consistent with their playing a role in synchronizing the firing of Purkinje cells within the same compartment.

Animals↗