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PubMed1987

Cajal-Smirnow ansiform fibers in the molecular layer of the rat cerebellar cortex.

The present light and electron microscopic study deals with the morphology and organization of Cajal-Smirnow ansiform fibers (AFs) in the molecular layer of the cerebellar cortex. The cerebella of normal adult rats were processed with Cajal's reduced silver method and conventional electron microscopy. With the silver method AFs appear as isolated elements or, more frequently, as small bundles of myelinated fibers, which emerge from the medullary rays, ascend through the granular, Purkinje cell and molecular layers and curve back to reenter the granular layer or cerebellar white matter. They traced an arciform trajectory of variable width and height in the molecular layer. Relatively large bundles of AFs were rarely found. The occurrence of AFs was confirmed in semithin sections as myelinated fibers of variable diameter ranging from 1 to 6 micron. Oligodendrocytes were often observed near AFs. At the ultrastructural level, the most common type of AF is large, with a relatively thin myelin sheath and a moderately dense axoplasm. Nodal or terminal synaptic differentiations were not observed. We suggest that AFs are misoriented cerebellar mossy fibers and their occurrence may be the consequence of a small-scale error in the axonal guidance of growing mossy fibers.

Animals↗

PubMed1994

Localization of NADPH-diaphorase/nitric oxide synthase activity in the rat cerebellar cortex: a light and electron microscopical study.

The activity of reduced nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) was examined histochemically in the rat cerebellar cortex at the light and electron microscopical level. Different staining patterns were observed depending on the technique used. Electron dense reaction product was seen on distinct membrane portions of the endoplasmic reticulum including the nuclear envelope in most of the neurons and in endothelial cells. Electron microscopically no activity staining was seen in glial cells, including Bergmann cells. The addition of the detergent Triton X-100, usually applied in the light microscopical diaphorase histochemistry, led to a striking diminution in membrane staining. In such preparations inspected electron microscopically formazan formed small granules which were evenly distributed over the cytoplasm.

Amino Acid Oxidoreductases↗

PubMed1981

Synaptic input to the axon hillock and initial segment of inhibitory interneurons in the cerebellar cortex of the rat. An electron microscopic study.

The axon hillock (AH) and initial segment (IS) of 10 Golgi neurons and 6 basket cells in the cerebellar cortex of the rat were investigated by electron microscopy using serial sections. An average of 10.4 and 11.3 synaptic terminals were observed to establish synaptic contact with the axon hillock region of Golgi and basket cells, respectively. Most of these terminals were identified as the varicosities of the ascending parallel fibers. It is suggested that the focal innervation of AH regions represents an excitatory input pattern which is basically different from the randomly distributed, huge, parallel-fiber input onto the dendritic trees of Golgi and basket cells. In contrast to Golgi and basket neurons, no accumulation of parallel-fiber synapses was observed around the AH of stellate cell. The IS proper of the three neuronal types were devoid of true axo-axonal synapses.

Animals↗

PubMed1978

[Responses of cat cerebellar cortex neurons to stimulation of the caudate nucleus, globus pallidus and substantia nigra].

Impulsive responses (IR) of the Purkinje cells (PC) and other units of the cerebellar cortex in the paramedian lobules, lobulus simplex and tuber vermis were evoked by stimulation of nucleus caudatus (NC) in cats under chloraloze-nembutal narcosis. The phasic IR as simple discharges (due to mossy fibre activation) were exhibited mainly with a latency of 5-12 and 14-20 ms; a latency of the compound responses ) due to climbing fibre PC activation) was equal to 5-6, 9-22 ms and more. There were differences in rhythmic reproduction of the responses depending on their latency. The recruitment responses were found during a 4-6/s NC stimulation. There was an inhibitory pause as an obligatory component of the tonic neuronal responses. Reactions of the same types (phasic and tonic) as in the case of the NC stimulation, but differing in unit's quantitative distribution according to the latency appeared in the globus pallidus (GP) stimulation. The minimal latency was 4 ms. Recruitment was observed as well. The substantia nigra (SN) stimulation evoked PC responses, activated by the climbing fibres with a stable latency (8.5 +/- 0.3 ms). SN, GP, n. inferior olive as well as thalamic nuclei are considered to play a definite role in realizing caudate-cerebellar connections, both oligosynaptic and polysynaptic.

Animals↗

PubMed1998

Noradrenergic influences on the cerebellar cortex: effects on vestibular reflexes under basic and adaptive conditions.

Experiments performed either in decerebrate cats or in intact rabbits have shown that functional inactivation of the cerebellar anterior vermis or the flocculus decreased the basic gain of the vestibulospinal or the vestibulo-ocular reflex, respectively. These findings were attributed to the fact that a proportion of the vermal or floccular Purkinje cells, which are inhibitory in function, discharge out of phase with respect to the vestibulospinal or the vestibulo-ocular neurons during sinusoidal animal rotation, thus exerting a facilitatory influence on the gain of the vestibular reflexes. Intravermal injection of a beta-noradrenergic agonist slightly increased the gain of the vestibulospinal reflex, whereas the opposite result was obtained after injection of beta-antagonists. Similarly, intrafloccular injection of a beta-noradrenergic agonist slightly facilitated the gain of the vestibulo-ocular reflex in darkness (but not in light), whereas a small decrease of the reflex occurred after injection of a beta-antagonist. It was postulated that the noradrenergic system acts on Purkinje cells by enhancing their amplitude of modulation to a given labyrinth signal, thus increasing the basic gain of the vestibular reflexes. The Purkinje cells of the cerebellar anterior vermis and the flocculus also exert a prominent role on the adaptation of vestibulospinal and vestibulo-ocular reflexes, respectively. In particular, intravermal or intrafloccular injection of beta-noradrenergic antagonists decreased or suppressed the adaptive capacity of the vestibulospinal and vestibulo-ocular reflexes that always occurred during sustained out-of-phase neck-vestibular or visual-vestibular stimulation, whereas the opposite result was obtained after local injection of a beta-noradrenergic agonist. The noradrenergic innervation of the cerebellar cortex originates from the locus coeruleus complex, whose neurons respond to vestibular, neck, and visual signals. It was postulated that this structure acts through beta-adrenoceptors to increase the expression of immediate-early genes, such as c-fos and Jun-B, in the Purkinje cells during vestibular adaptation. Induction of immediate-early genes could then represent a mechanism by which impulses elicited by sustained neck-vestibular or visuovestibular stimulation are transduced into long-term biochemical changes that are required for cerebellar long-term plasticity.

Adaptation, Physiological↗

PubMed1994

Morphology of parallel fibres in the cerebellar cortex of the rat: an experimental light and electron microscopic study with biocytin.

Microinjections of biocytin have been made in the granular layer of the rat cerebellar cortex in order to label the axonal projections of a localised population of granule cells. Light microscopic techniques were used to determine the lengths of the parallel fibres and to measure the spacing and size of the fibre varicosities. Fibres were longest in the superficial one-third of the molecular layer, where mean overall length was 4.7 mm, and mean length decreased to 4.2 mm in the lower one-third of the molecular layer. We found no very short fibres but a small population deep in the molecular layer had a branch length of about one-half the average. Mean intervaricosity interval and varicosity size varied with distance from proximal to distal along the fibres. Mean intervaricosity interval was 3.7 microns within 250 microns of the fibre bifurcation points and progressively increased towards the distal ends, where the mean interval was 7.4 microns. Mean varicosity size was 0.82 microns 2 in this proximal region and decreased to 0.47 microns 2 about 1.2 mm distally. Mean intervaricosity interval on the ascending axons of the granule cells was 4.0 microns. Electron microscopy revealed that a high proportion (89%) of the parallel fibre varicosities formed synaptic junctions. The majority of the synapses (91%) were formed on Purkinje cell dendritic spines. Some varicosities also formed simultaneous synaptic contacts or double synapses with two spines. These double synapses occurred more frequently in the proximal region of the fibres (11%) than on the distal ends (2%). The length of the postsynaptic density also differed according to the location of the varicosities and the mean length at the proximal parallel fibre synapses was 0.59 microns compared with 0.38 microns at the distal synapses. It is concluded that a beam or bundle of parallel fibres originating from cells in a focal region of the granular layer will exert a graded synaptic influence on its target Purkinje cells, with the most powerful influence occurring on cells located around the proximal region of the fibres where they bifurcate and the weakest action being exerted on cells located at the distal end of the fibres.

Animals↗

PubMed1988

[The ratio of the types of gliocytes in the cerebellar cortex of mice during malnutrition and subsequent nutritional rehabilitation].

Different types of glial cells were counted on the semithin sections on the area 0.5 mkm2 of the cerebellar cortex of mice and percent relation of glyocytes-satellites of glyocyte types was determined. The malnutrition in early postnatal life has been found to cause the aberration in the process of glyocytes differentiation, especially in the population of oligodendrocytes. After the food rehabilitatin the processes of differentiation normalize that expresses in the increase of proportion of olygodendrocytes and olygodendrocytes satellities up to the control.

Aging↗

PubMed1976

Quantitative morphological studies of developing human cerebellar cortex in various disease states.

A quantitative morphological assessment was carried out of the cellularity and staining properties of the cells of the layers of the human cerebellar cortex, both in the normal child and in 41 children suffering from a series of disorders including mental retardation. A computerized image analyser and highly standardized procedures were used. All of the cases of mental retardation and some cases with congenital cardiac anomalies showed abnormal cell concentrations and staining properties. 3 cases of 'cot death' also showed abnormal results. These findings are presented as a new measurable aspect of brain disease, and as a indication for further study.

Cerebellar Cortex↗

PubMed1997

[NO-ergic function of the Lugaro and Golgi cells in the rabbit cerebellar cortex].

The distribution of NADPH-diaphorase was studied cytochemically in the rabbit cerebellar cortex. In the granular layer the Golgi cells with positive reaction were found. The highest activity of enzyme was observed in the cytoplasm of intermediate cells of Lugaro, synaptic neurons of Landau, large and middle sized Golgi cells and intercalate cells of Pensa. It is concluded that the Lugaro and Golgi cells may metabolize nitric oxide to be NO-ergic in their mediator specialization.

Animals↗

PubMed1997

Laminar analysis of activity-dependent increases of CBF in rat cerebellar cortex: dependence on synaptic strength.

The purpose of the present study was to examine mechanisms of activity-dependent changes of cerebral blood flow (CBF) in rat cerebellar cortex by laser-Doppler flowmetry, using two synaptic inputs that excite different regions of the same target cell and with different synaptic strength. The apical part of Purkinje cells was activated by electrical stimulation of parallel fibers, whereas the cell soma and the proximal part of the dendritic tree were activated by climbing fibers using harmaline (40 mg/kg ip) or electrical stimulation of the inferior olive. Glass microelectrodes were used for recordings of field potentials and single-unit activity of Purkinje cells. CBF increases evoked by parallel fibers were most pronounced in the upper cortical layers. In contrast, climbing fiber stimulation increased CBF in the entire cortex. Inhibition of nitric oxide (NO) synthase activity by NG-nitro-L-arginine (L-NNA) or guanylate cyclase activity by 1H-[1,2,4(oxadiazolo)4,3-a]quinoxaline-1-one did not affect basal or harmaline-induced Purkinje cell activity but attenuated harmaline- and parallel fiber-evoked CBF increases by approximately 40-50%. Application of 8-(p-sulfophenyl)theophylline and adenosine deaminase reduced the harmaline-evoked CBF increase without any effect on the parallel fiber-evoked CBF response. The results suggest that CBF increases elicited by activation of Purkinje cells are partially mediated by the NO-guanosine 3',5'-cyclic monophosphate system independent of the input function but that adenosine contributes as well when climbing fibers are activated. This is the first demonstration of variations of coupling as a function of postsynaptic activity in the same cell.

Analysis of Variance↗

PubMed1990

Interactions between astroglia and ectopic granule cells in the cerebellar cortex of normal adult rats: a morphological and cytochemical study.

The cytology and organization of astroglial cells associated with ectopic granule cells (EGCs) have been studied in the cerebellar cortex of normal adult rats, using Golgi preparations, immunohistochemistry against the glial fibrillary acidic protein (GFAP) and ultrastructural analysis. Elongated perikarya of EGCs scattered in the molecular layer were usually attached to radial Bergmann fibers, which exhibited a normal morphology. A second configuration of EGCs consisted of intrafissural colonies of ectopic neurons. The molecular layer that surrounded these ectopic colonies showed disorientation of both Bergmann fibers and parallel fibers. Within the ectopic tissue, typical velate astrocytes were commonly observed. They formed homologous associations with EGC perikarya and cerebellar glomeruli. However, a restricted astroglial plasticity was detected in the form of heterologous interactions between astrocytes and Purkinje cell dendrites, including their associated synapses with parallel fibers. In spite of this astroglial plasticity, our results suggest that in the physiological systems of granule cell ectopia studied here, the different specific interactions of Bergmann glia and astrocytes with neurons tend to be conserved.

Animals↗

PubMed1997

Lesion-induced neuronal nitric oxide synthase in Purkinje cells of the rat cerebellar cortex: histochemical and in situ hybridization study.

Lesion-induced induction of neuronal nitric oxide synthase (nNOS) was examined in the rat cerebellum. The stab-lesioned cerebellar cortex was examined with NADPH-diaphorase (NADPH-d) histochemistry and in situ hybridization using nNOS cRNA probe at 1, 3, 7, 14, 35 days post-lesion. NADPH-d- and nNOS mRNA-positive Purkinje cells appeared adjacent to the lesion by 3 days after the lesion. The area of distribution expanded and the number of positive cells increased at 7 days after the lesion, and at 14 days post-lesion, shrunken NADPH-d-positive Purkinje cells with irregular surface appeared. NADPH-d activity and nNOS mRNA signal could not be detected in Purkinje cells after 35 days post-lesion. Combined NADPH-d histochemistry and in situ hybridization using glutamic acid decarboxylase (GAD) cRNA probe revealed that nNOS-expressing Purkinje cells showed fewer GAD mRNA signals than those in normal Purkinje cells. The atrophic contour and the lower expression of GAD mRNA signals in NADPH-d positive Purkinje cells suggest that nNOS is expressed under a degenerating process.

Animals↗

PubMed1976

The length of parallel fibers in the cat cerebellar cortex. An experimental light and electron microscopic study.

Experimental light and electron microscopic studies were carried out to determine the length of parallel fibers in the cat cerebellar cortex. Using a fine surgical knife, vermal and hemispheral folia were cut perpendicular to their long axis. The animals were sacrificed 1-10 days after the operation. Sections of the transected folia were then stained with a Fink-Heimer procedure. The resulting degeneration appeared as fine dots that extended lateral to the lesion, as predictable from the course of the parallel fibers. Densitometer readings indicate that the density of degeneration declines gradually lateral to the lesion. The specificity of the silver impregnation was checked by processing silver stained sections for electron microscopy. This confirmed the location of the silver precipitate on degenerating parallel fibers. The pattern of parallel fiber degeneration in the molecular layer has a trapezoidal configuration centered on the lesion. The shorter parallel fibers are located at the base of the molecular layer and extend for 5 mm. The parallel fibers become progressively longer as they approach the pial surface where they attain a maximum length of 7 mm. Our studies suggest that in folia longer than 7 mm parallel fibers are 6 mm long on the average. In addition, it was determined on Golgi sections that the average center-to-center distance between en passant boutons of individual parallel fibers is 5.2 mum. The data indicate that an average parallel fiber, 6 mm long, forming approximately 1100 boutons, may synapse with each Purkinje dendritic tree it traverses.

Animals↗

PubMed2004

Analysis of the effects of cannabinoids on synaptic transmission between basket and Purkinje cells in the cerebellar cortex of the rat.

The hypothesis of the present work was that activation of CB1 cannabinoid receptors inhibits GABAergic neurotransmission between basket and Purkinje cells in the cerebellar cortex. The aim was to test this hypothesis under near-physiological conditions. Action potentials of basket cells and spontaneous inhibitory postsynaptic currents (sIPSCs) in synaptically coupled Purkinje cells were recorded simultaneously in rat brain slices. The cannabinoid agonists (R)-(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl) methyl] pyrrolo[1,2,3-de]-1,4-benzoxazinyl]-(1-naphthalenyl)methanone mesylate (WIN 55212-2) and (-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)-phenyl]-trans-4-(3-hydroxy-propyl)-cyclohexanol (CP55940) decreased the amplitude of sIPSCs occurring simultaneously with basket cell action potentials and lowered the success rate of synaptic transmission. These effects were prevented by the CB1 receptor antagonist N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichloro-phenyl)-4-methyl-3-pyrazole-carboxamide (SR141716). Depolarization of Purkinje cells also led to suppression of neurotransmission; prevention of this suppression by CP55940 and SR141716 indicates that endocannabinoids released from Purkinje cells were involved. WIN 55212-2 lowered the amplitude of autoreceptor currents recorded in basket cells (autoreceptor currents are due to the action of GABA released from axon terminals on GABAA autoreceptors of the same axon terminals); this is novel proof of the presynaptic action of cannabinoids. Autoreceptor current experiments also indicated that endogenous cannabinoids are not released by basket cell axon terminals. A presynaptic action is additionally supported by the observation that WIN 55212-2 lowered the frequency of miniature IPSCs recorded in the presence of tetrodotoxin and the calcium ionophore ionomycin. In conclusion, activation of CB1 receptors by exogenous cannabinoids and by endogenous cannabinoids released by Purkinje cells presynaptically inhibits GABAergic neurotransmission between basket and Purkinje cells. This was demonstrated under near-physiological conditions: transmitter release was elicited by action potentials generated by spontaneously firing intact presynaptic neurons.

Animals↗

PubMed1987

Reacquisition of classical conditioning after removal of cerebellar cortex.

We trained rabbits with white noise and light conditioned stimuli and a face shock unconditioned stimulus for classical conditioning of the nictitating membrane response and then removed the ipsilateral cerebellar cortex by aspiration. Larsell's hemisphere lobule VI was completely removed in 5 rabbits; the pattern of degeneration in the inferior olive matches the projections to HVI reported in experiments with horseradish peroxidase. All rabbits showed an initial abolition of conditioned responses but then relearned within two days. This indicates that cerebellar cortical lobule HVI normally is involved but is not necessary for classical conditioning.

Animals↗

PubMed1990

Acute phase proteins are present in amorphous plaques in the cerebral but not in the cerebellar cortex of patients with Alzheimer's disease.

Using immunohistochemical staining for beta-amyloid proteins in the brains of Alzheimer patients two basic types of plaques can be found: 'amorphous' or 'diffuse' non-congophilic plaques and classical plaques. Acute phase proteins alpha 1-antichymotrypsin, complement factors and P-component ('plaque-associated molecules') have been reported in both types of plaques in the cerebral cortex. In the present study we could not find immunoreactivity for these acute phase proteins in the amorphous plaques in the cerebellar cortex. These proteins seem to be essential for formation of classical plaques.

Acute-Phase Proteins↗

PubMed1975

Response of cat cerebellar vermis induced by sound. II. The role of the mossy and climbing fibers in acoustic transmission to the cerebellar cortex and influence of stimuli parameters.

Experiments were performed on cats under Chloralose or Nembutal anesthesia. The parameters of the acoustic click stimuli were found to have a strong influence on the responses registered from both the surface of the cerebellar vermis lobuli V up VII as well as from single units. It was shown that a stimulus frequency rate not greater than 1/2 s should be used, since higher frequencies caused strong attenuation of the response. The type of anesthesia did not change the latencies of reactions of both evoked potentials and single units. However, decreasing the strength of the click resulted in increased response latencies, in the case of single unit reactions. A very strong influence of weak visual stimuli on units was also observed. It is suggested that mossy fibers are the most important fibers in the transmission of acoustic information to the cerebellar cortex.

Acoustic Stimulation↗

PubMed1984

Lateral distribution of intramembrane particles in Purkinje and granule cells of the rat cerebellar cortex.

The lateral distribution of intramembrane protein particles (IMP) in the plasma membrane of Purkinje and granule cells was quantitatively assessed in freeze-fracture replicas of the rat cerebellar cortex. In the plasma membrane of each cell type this technique showed domains with statistically significant differences in the distribution of IMP. The values were highly reproducible between different animals fixed in comparable conditions. This analysis provides an additional parameter (besides the number and size of IMP) in the assessment of neuronal membrane heterogeneity.

Animals↗