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PubMed1992

GABAA, GABAB, and benzodiazepine binding sites in the cerebellar cortex of the red-eared turtle (Pseudemys scripta).

We used receptor autoradiography to ascertain the distribution of GABAA and GABAB binding sites in the cerebellar cortex of the red-eared turtle (Pseudemys scripta). GABAA binding sites were found in both molecular and granule cell layers with highest levels in the granule cell layer. GABAB binding sites were found at highest level in the molecular layer. Benzodiazepine binding sites were found in approximately equal abundance in both layers. Little binding of any ligand was seen in the Purkinje cell layer. Our results are similar to those found in mammals and other non-mammalian vertebrates and indicate that the organization of inhibitory pathways of the cerebellar cortex has been conserved in the course of vertebrate evolution.

Animals↗
PubMed1998

Selective synaptic plasticity within the cerebellar cortex following complex motor skill learning.

Complex motor skill learning, but not mere motor activity, leads to an increase in synapse number within the cerebellar cortex. The present experiment used quantitative electron microscopy to determine which synapse types were altered in number. Adult female rats were allocated to either an acrobatic condition (AC), a voluntary exercise condition (VX), or an inactive condition (IC). AC animals were trained to traverse an elevated obstacle course requiring substantial motor coordination to complete. VX animals were housed with unlimited access to running wheels and IC animals received no motor training but were handled briefly each day. Results showed the AC animals to have significantly more parallel fiber to Purkinje cell synapses than both the VX and IC animals. No other synapse type was significantly altered. Thus, the learning-dependent increase in synapse number observed within the cerebellar cortex is accomplished primarily through the addition of parallel fiber synapses.

Analysis of Variance↗
PubMed2001

Morphometric analysis of the cerebellar cortex capillaries in the course of experimental valproate encephalopathy and after chronic exposure to sodium valproate using transmission electron microscopy.

Morphometric analysis of the cerebellar cortex capillary cross-section area performed in experimental valproate encephalopathy using transmission electron microscopy showed that prolongation of VPA application resulted in more enhanced lumen narrowing manifested in gradual reduction in the mean value of the coefficient examined. After 6, 9 and 12 months of experiment this value was statistically different from that obtained in control subgroups, being respectively lower by approximately 22%, 48% and 65%. One month after terminating of chronic administration this value was close to the one found after 12 months of the study. Three months after the drug withdrawal the coefficient was higher by approximately 44% compared to the one after 12 months, which seemed to indicate an increase in capillary lumen patency. The morphometric analysis of the cerebellar cortex capillary cross-section area performed in the present study objectifies the results of qualitative ultrastructural investigations concerning the microcirculation of this CNS structure.

Animals↗
PubMed1996

Morphological features of encephalopathy after chronic administration of the antiepileptic drug valproate to rats. A transmission electron microscopic study of capillaries in the cerebellar cortex.

Long-term intragastric application of the antiepileptic drug sodium valproate (Vupral "Polfa") at the effective dose of 200 mg/kg b. w. once daily to rats for 1, 3, 6, 9 and 12 months revealed neurological disorders indicating cerebellum damage ("valproate encephalopathy"). The first ultrastructural changes in structural elements of the blood-brain-barrier (BBB) in the cerebellar cortex were detectable after 3 months of the experiment. They became more severe in the later months of the experiment, and were most severe after 12 months, located mainly in the molecular layer of the cerebellar cortex. Lesions of the capillary included necrosis of endothelial cells. Organelles of these cells, in particular the mitochondria (increased number and size, distinct degeneration of their matrix and cristae) and Golgi apparatus were altered. Reduced size of capillary lumen and occlusion were caused by swollen endothelial cells which had luminal protrusions and swollen microvilli. Pressure on the vessel wall was produced by enlarged perivascular astrocytic processes. Fragments of necrotic endothelial cells were in the vascular lumens and in these there was loosening and breaking of tight cellular junctions. Damage to the vascular basement lamina was also observed. Damage to the capillary was accompanied by marked damage to neuroglial cells, mainly to perivascular processes of astrocytes. The proliferation of astrocytes (Bergmann's in particular) and occasionally of oligodendrocytes was found. Alterations in the structural elements of the BBB coexisted with marked lesions of neurons of the cerebellum (Purkinje cells are earliest). In electron micrographs both luminal and antiluminal sides of the BBB of the cerebellar cortex had similar lesions. The possible influence of the hepatic damage, mainly hyperammonemia, upon the development of valproate encephalopathy is discussed.

Animals↗
PubMed1998

Expression of the nicotinic acetylcholine receptor alpha4 subunit mRNA in the rat cerebellar cortex.

In order to compare the previous immunohistochemical and immunocytochemical data on the distribution of nicotinic acetylcholine receptor alpha4 subunit-like immunoreactivity with the expression of alpha4 mRNA in the rat cerebellar cortex, the present study determined the cellular distribution of alpha4 mRNA in the rat cerebellar cortex. Northern blot analysis revealed two alpha4 mRNA bands in the rat cerebellum and three in the cerebral cortex, hippocampus, hypothalamus and striatum. The total level of these transcripts was lower in the cerebellum than in the other four regions. The expression of alpha4 mRNA was high in Purkinje cells and granular cells, whereas low expression was detected in the molecular layer. These results suggest that the expression of alpha4 mRNA is closely related to the alpha4-like immunoreactivity in the molecular and Purkinje cell layers. In the granular layer, alpha4 mRNA was very highly and broadly expressed in comparison with the alpha4-like immunoreactivity.

Animals↗
PubMed1985

The size and curvature of synapses in the cerebellar cortex of the cat.

At the supra Purkinje layer and the subpial level in the molecular layer of lobules V and VI of the cerebellar cortex of the cat, synaptic profiles were measured in ultrathin serial sections treated with either osmium tetroxide (OsO4) or ethanolic phosphotungstic acid (E-PTA). From trace and chord lengths of the intercepts of synaptic profiles the curvature and the mean caliper diameter of the synapse was calculated. In OsO4-material the curvature of synapses yielded an average angle of about 47 degrees and about 36 degrees in E-PTA material. Although these values are contrary to the assumption of a flat disc, which is commonly required in stereological procedures to estimate caliper diameter, the effect of the curvature on the estimation of the mean caliper diameter is limited. This is shown by serial reconstruction analysis of the largest diameter of synapses from maximal arc and chord length measurements at the subpial and supra Purkinje level. The results provide quantitative data concerning synaptic size, curvature and the frequency of intercepts per synapse at the subpial and supra Purkinje level in the cerebellar cortex in OsO4 and E-PTA material. In addition the advantages and disadvantages of E-PTA and osmiumtetroxide staining in quantitative analysis are discussed.

Animals↗
PubMed1991

A neural network model of the cerebellar cortex performing dynamic associations.

The present paper proposes a model which applies formal neural network modeling techniques to construct a theoretical representation of the cerebellar cortex and its performances in motor control. A schema that makes explicit use of propagation delays of neural signals, is introduced to describe the ability to store temporal sequences of patterns in the Golgi-granule cell system. A perceptron association is then performed on these sequences of patterns by the Purkinje cell layer. The model conforms with important biological constraints, such as the known excitatory or inhibitory nature of the various synapses. Also, as suggested by experimental evidence, the synaptic plasticity underlying the learning ability of the model, is confined to the parallel fiber--Purkinje cell synapses, and takes place under the control of the climbing fibers. The result is a neural network model, constructed according to the anatomy of the cerebellar cortex, and capable of learning and retrieval of temporal sequences of patterns. It provides a framework to represent and interpret properties of learning and control of movements by the cerebellum, and to assess the capacity of formal neural network techniques for modeling of real neural systems.

Animals↗
PubMed1994

Diazepam binding inhibitor fragment 33-50 (octadecaneuropeptide) immunoreactivity in the cerebellar cortex is restricted to glial cells.

The distribution of octadecaneuropeptide (ODN)-like immunoreactivity (LI) and its relationship to gamma-aminobutyric acid (GABA)-LI were investigated in the cerebellar cortex of adult rats with electron microscopy. At the electron microscopic level, ODN-LI was found exclusively in glial cells. In addition to Bergmann glia and its processes, cerebellar astrocytes were also labelled, encapsulating unlabelled neuronal elements of the cerebellum. These ODN-LI glial processes were observed in close apposition to synaptic junctions, but immunoreactivity could not be found in the synaptic cleft or in association with neuronal membranes. Since GABA-LI is always associated with neuronal elements, the colocalization of GABA- and ODN-LI could not be confirmed in the cerebellar cortex. Our results do not support the assumption that ODN is a neuron-specific processing product of diazepam binding inhibitor.

Animals↗
PubMed1978

[Differentiation of astroglial cells of the cerebellar cortex in the postnatal development of the rat: a morphological and histochemical study].

The morphological autoradiographic and cytospectrophotometric analysis of proliferation and differentation of the cerebellar cortex astroglial cells has been carried out during the rat early postnatal development. The proliferating astroglial cells constitute a major part of the whole cell population of the internal granular layer during the first week. It was proved by means of double labelling (3H- and 14C-thymidine) that these cells synthesize DNA and divide repeatedly, their division proceeding without preliminary morphological dedifferentiation, i. e. with the preservation of plasmatic processes. A suggestion is put forward that the precursors of the cerebellar cortex astroglial cells under study take their origin from the subependymal zone during the prenatal development. The results obtained allow to identify the proliferating glial cells as the Bergman's glia.

Age Factors↗
PubMed1996

Immunocytochemical localization of mGluR1a metabotropic glutamate receptor in inhibitory interneurons of the cerebellar cortex.

Immunocytochemical investigation of metabotrop glutamate receptor la in the cerebellar cortex of rat revealed a presence of this receptor in all cortical inhibitory nerve cells (Purkinje, basket, stellate, Lugaro and Golgi). In addition to the previously described localization of this receptor in Purkinje dendritic spines supplied by parallel and climbing fibres and considered to be responsible for cerebellar long-term depression, we have observed metabotropic glutamate receptor la immunopositivity also in the synapses between parallel fibres and dendrites of basket, stellate and Golgi neurons. The postsynaptic receptor was also present occasionally in inhibitory synapses between stellate cell axons and Purkinje cells as well as between Purkinje axon collaterals and Lugaro cell dendrites. The possibility, that mGluR1a receptors in basket, Golgi and stellate cells might directly or indirectly contribute to cerebellar LTD, is discussed.

Animals↗
PubMed2003

Anisotropic representation of forelimb position in the cerebellar cortex and nucleus interpositus of the rat.

The relationship between the spatial location of limb and the activity of cerebellar neurons has received little attention and its nature still remains ambiguous. To address this question we studied the activity of Purkinje and nucleus interpositus cells in relation to the spatial location of rat forelimb. A computer-controlled robot arm displaced the limb passively across 15 positions distributed on a parasagittal plane. The limb was upheld for 8 s in each position, which was identified by the Cartesian coordinates of the forepaw. We selected the neurons whose activities were significantly modulated by forepaw position and found that the majority represented preferentially one spatial dimension of the Cartesian plane both in the cerebellar cortex and nucleus interpositus. In particular, the antero-posterior axis was best represented in cerebellar neuronal discharges. This result suggests that the intermediate part of the cerebellum might encode limb position by way of an anisotropic representation of the spatial coordinates of the limb end-point.

Action Potentials↗
PubMed1987

Thyroid hormone modulates the expression of a neurofilament antigen in the cerebellar cortex: premature induction and overexpression by basket cells in hyperthyroidism and a critical period for the correction of hypothyroidism.

Neurofilament expression by basket cells of the cerebellar cortex is suppressed in hypothyroidism. By using a monoclonal antibody (mabN210) that selectively recognizes an epitope associated with the 210-kDa neurofilament subunit, we have explored the relationship between thyroid hormone levels and basket cell maturation. In animals rendered hypothyroid by inclusion of propylthiouracil in the maternal drinking water from embryo age E17, there is a complete absence of mabN210 immunoreactivity in the basket cell axons, while the other immunoreactive axons in the cerebellar cortex, primarily Purkinje cell axons and mossy fibers, are apparently unaffected. This deficit can be corrected by treatment with thyroid hormone but there seems to be a critical period for full recovery, for animals treated from birth recover normally whereas there is a gradual diminution in the efficacy of treatment the later it begins. Thyroid hormone therapy begun after postnatal day 30 (P30) leads only to very minor recovery. By contrast, animals on a hyperthyroid regime show premature mabN210-antigen induction in the basket cells and supranormal levels of expression at P25, despite the severe reduction in the number of basket cell somata. This suggests either abnormal compensatory sprouting of axon collaterals by the remaining basket cells or the occurrence, during normal cerebellar corticogenesis, of competition between basket cell axons for a limited number of Purkinje cell targets followed by the elimination of the excess collaterals.

Animals↗
PubMed1982

Presynaptic dendrites and perikarya in deafferented cerebellar cortex.

Two to 30 days after complete isolation of the cerebellar cortex of adult rats, small Golgi II type neurons in the granular layer develop presynaptic sites on their dendrites and perikarya. The newly developed presynaptic dendrites established dendrodendritic synaptic contacts with dendritic digits of granule cells. In addition, some granule cells were observed to develop presynaptic sites on their somata and dendritic digits, resulting in the formation of (sometimes reciprocal) dendrodendritic synapses between granule cells or between granule cells and Golgi neurons. The development of these unusual synaptic formations indicates a persisting synaptic plasticity of these two cerebellar cell types. It is suggested that this unorthodox synapse formation develops as part of a reactive compensatory process to synaptic desaturation brought about by the deafferentation of the cerebellum.

Afferent Pathways↗
PubMed1971

Human fetal cerebellar cortex: organization and maturation of cells in vitro.

Human fetal cerebellar cortex was maintained up to 5 months in vitro. Important features included early migration of granule neurons followed by maturation of Purkinje and granule neurons. Unique areas of organization developed in which a rim of leptomeningeal cells surrounded an explant and its outgrowth zone; these areas subsequently grew as well-defined units.

Cell Nucleus↗
PubMedDate not supplied

[The neuronal electrical activity of the cerebellar cortex in hypoxia].

The dynamics of impulse activity of the cerebellar cortex neurons demonstrated in acute experiments on nembutal-anesthetized and diplacinum-immobilized cats bore evidence that the cerebellum participates in the organism's response to hypoxia. The Purkinje cells proved to be more resistant to hypoxia than the neurons of the neopallium, archipallium, and some other structures of the brain stem.

Action Potentials↗
PubMed1978

Ultrastructure of astroglial contacts in rat cerebellar cortex.

Interfaces of the astroglial Bergmann fibres in the rat cerebellar cortex were investigated under the electron microscope. The straight interfaces revealed numerous contacts of a special junctional type having a mean length of 0.9 micro m. A substantial area of the Bergmann fiber surfaces was found to be connected with these junctions. Electron-dense material forming knoblike particles were observed attached with a certain regularity to the inner surfaces of both junctional membranes.

Animals↗
PubMedDate not supplied

Density and pattern of dopamine D2-like receptors in the cerebellar cortex of aged rats.

The pharmacological properties and the anatomical localization of dopamine (DA) D2-like receptors were studied in the cerebellum of 3 months, 12 months, and 24 months male Wistar rats using combined radioligand binding and autoradiographic techniques with [3H]-spiroperidol as a ligand. The binding was consistent with the labelling of the DA D3 receptor subtype. The affinity for DA D2-like receptors was similar in the cerebellar cortex of the three animal groups investigated, whereas the density of binding sites (Bmax value) assessed using conventional radioligand binding techniques was reduced as a function of aging. Light microscope autoradiography revealed the localization of binding sites primarily in the molecular layer and to a lesser amount in Purkinje neurons layer. A loss of binding sites was noticeable with aging in the grey matter of the cerebellar cortex. It affected primarily the molecular layer. Analysis of radioligand binding data and light microscope autoradiography suggests that age-related changes of DA D2-like receptors depend in part by structural alterations of cerebellar cortex and in part by modifications in receptor expression.

Aging↗
PubMed1979

Comparative studies on the pre- and postterminal blood vessels in the cerebellar cortex of Rhesus monkey, cat, and rat.

In the rhesus monkey, cat and rat, pial arteries give off branches which run vertically through all three layers of the cerebellar cortex. The large cortical arteries are surrounded by a perivascular space in the molecular layer. Their wall consists of several layers of smooth-muscle cells and the luminal endothelium. As the arteries reach the deeper layers of the cerebellar cortex, the number of smooth-muscle cells is reduced. In the rat, sometimes no smooth-muscle cells are detectable in the preterminal arterial vessels. If these deep arteries branch off by dichotomy of terminal vessels there occurs a gradual or complete loss of myocytes in all three species. In the cat, where cortical arteries give off branches at right angles, there is a sphincter-like accumulation of smooth-muscle cells at the opening to the smaller branch. The postterminal vessels and veins in all species exhibit the same mural structure found in capillaries. The wall consists only of an endothelium and occasional pericytes embedded in the basal lamina. Even the large veins which run to the pial veins show this simple mural structure.

Animals↗