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At least 19 recordsLinked to original sources
PubMed1992

Dopaminergic and non-dopaminergic neurons in the ventral tegmental area of the rat project, respectively, to the cerebellar cortex and deep cerebellar nuclei.

It has been suggested recently that dopamine in the cerebellum not only acts as a precursor for noradrenaline in afferent fibers supplied by locus coeruleus neurons, but also subserves an independent transmitter role in a separate neural system. The present study was initiated to investigate the possible sources for dopaminergic innervation of the cerebellum. Employing anterograde and retrograde axonal tracing with cholera toxin and a combination of fluorescent retrograde axonal tracing with Fluoro-Gold and tyrosine hydroxylase immunofluorescence histochemistry, we found in the rat that the ventral tegmental area, containing the A10 dopaminergic cell group, sends projection fibers to the cerebellum bilaterally with a slight contralateral predominance. The projections from the ventral tegmental area to the cerebellum were segregated into the dopaminergic one to the cerebellar cortex and the non-dopaminergic one to the deep cerebellar nuclei. Dopaminergic fibers projecting from the ventral tegmental area to the cerebellar cortex terminated mainly in the granular layer, additionally in the Purkinje cell layer, but not at all in the molecular layer. They were distributed predominantly in the crus I ansiform lobule and paraflocculus, and to a lesser extent in the crus II ansiform lobule. On the other hand, non-dopaminergic fibers projecting from the ventral tegmental area to the deep cerebellar nuclei were seen to terminate mainly in the lateral nucleus, to a lesser extent in the interpositus nucleus, but not at all in the medial nucleus. The ventral tegmental area was also observed to receive projection fibers from the lateral and interpositus cerebellar nuclei bilaterally with a contralateral predominance. The projections from the ventral tegmental area to the cerebellum revealed in the present study might exert limbic influences upon the cerebro-cerebellar loops subserving the execution and co-ordination of voluntary movements.

Animals↗
PubMed1979

The organization of afferents to the cerebellar cortex in the cat: projections from the deep cerebellar nuclei.

The topography of the cerebellar nucleo-cortical projection was investigated in the cat by experiments employing the horseradish peroxidase (HRP) technique or by combined HRP-autoradiographic methods. The results of the HRP studies extend previous findings showing that neurons in the deep nuclei project to the cerebellar cortex in an orderly way. Thus, it appears that the cortex of the vermis-proper receives projections from neurons located predominately in the fastigial nucleus. Intermediate and lateral zones of mid-vermal cerebellar cortex are projected on by neurons located in the interposed and dentate nuclei. Crus II receives input from neurons located predominately in the dentate nucleus, while the paramedian lobule is projected on by neurons located in a large postero-dorsal sector of the interposed nucleus and in a smaller medial strip of the dentate nucleus. Neurons in the ventral part of the dentate nucleus and the lateral part of the interposed nucleus send fibers to the paraflocculus. The nucleo-cortical pathway to the flocculus and nodulus arises largely from a population of neurons located in a ventral region stretching from the medial border of the dentate nucleus to the lateral border of the fastigial nucleus. The results of experiments using the combined HRP-autoradiographic method show that clusters of neurons in the deep cerebellar nuclei project back to the cerebellar cortical areas from which they receive input, establishing a fairly precise feedback loop between the cerebellar cortex and deep nuclei.

Afferent Pathways↗
PubMed1975

The differential effect of cooling on responses of cerebellar cortex.

1. Responses of the cerebellar cortex in anaesthetized cats were evoked by mossy fibre and/or climbing fibre inputs, and the effects of graded cooling of the cerebellar cortex were investigated. Cooling was applied either globally by flooding the exposed cortex with cooled Ringer Locke, or in later experiments locally be passing cooled fluid through a silver tube in contact with the cerebellar cortex. The cortical temperature was continuously monitored by a thermistor inserted to a depth of 0.5 mm close to the recording site. 2. In the granular layer the cooling caused a large increase in the diphasic P1N1 wave generated by the afferent mossy fibre volley. The waves generated by synaptic excitation and discharge of granule cells, N2P2, were not diminished until the temperature fell towards 20 degrees C. In contrast the N3 wave of the molecular layer was largest with cooling in the range of 35 to 25 degrees C, often several times larger than at 38 to 40 degrees C. Associated with the enhanced N3 wave there was an enhanced N4 wave, which indicates an increased discharge by Purkynĕ cells. 3. Climbing fibre inputs generate a negative field potential in the molecular layer due to the powerful excitation of Purkynĕ cells. In contrast to the N3 potential this climbing fibre wave was largest at the higher temperatures 35-40 degrees C and declined progressively with cooling, being usually suppressed at moderate coolings of 31-27 degrees C. Intracellular recording revealed that the diminution was due both to the elimination of all but the first impulses of the normal burst discharge of the climbing fibre impulses and to the diminution of the synaptic excitation of a single climbing fibre impulse. 4. It is shown that the negative potentials produced in the molecular layer by combinations of mossy fibre and climbing fibre inputs can be very effectively distinguished by this differential effect of cooling. 5. The effects of cooling even to a severe level are immediately recoverable on warming. Repeated cooling has no untoward effects and there is no sign of the hysteresis reported for the cuneate nucleus. 6. There is a discussion of the factors that could cause cooling to differentiate between the actions of the mossy fibre and climbing fibre impulses on Purkynĕ cells.

Action Potentials↗
PubMed1979

Identification of early glial elements as the precursors of Bergmann-glia: a Golgi-analysis of the developing rat cerebellar cortex.

The developing rat cerebellar cortex was studied by the rapid Golgi procedure in 200 mu thick slices and in 1--2 mu thick semithin sections poststained with toluidine-blue. Glial cells having radial fibres directed towards the pial surface were found to be present continuously in the internal granular layer during cerebellar maturation. This cell type was identified as the developing Bergmann-glia.

Animals↗
PubMed1976

The myelinated parallel fibers of the cerebellar cortex and their regional distribution.

In the cerebellar cortex of the Rhesus monkey and the cat, the supraganglionic plexus in the molecular layer exhibits regional differences. The plexus is very well developed in the vermal parts of the anterior lobe, but only poorly developed in the nodulofloccular lobe. Most of the fibers of this plexus are myelinated parallel fibers, which synapse in the typical manner with dendritic thorns of Purkinje cells. Only very few fibers of this plexus are recurrent collaterals of Purkinje cells. Their distribution throughout the cerebellar cortex does not display regional differences. These findings agree with physiological data on the disinhibition of Purkinje cells in different parts of the cerebellar cortex.

Animals↗
PubMed1976

Electrophysiological study on the postnatal development of neuronal mechanisms in the rat cerebellar cortex.

(1) Functional commencements of the neuronal elements in the cerebellar cortex of young rats were studied electrophysiologically by means of laminar field potential analyses in the cortex on stimulation of the cerebellar surface (Loc) and the white matter (WM). (2) The antidromic action potential of Purkinje cells on the WM stimulation was observed at one day after birth. The climbing fiber excitation of Purkinje cells on the stimulation was noted at 3 days after birth. (3) The mossy fiber-granule cell synapses were found to function at 10 days after birth and the Golgi cell inhibition of granule cells could be proved at the same time. The excitatory action of parallel fibers and the inhibitory action of basket-stellate cells on Purkinje cells appeared simultaneously at about 12 days after birth. The transverse distribution across the cerebellar folium of the basket-stellate cell inhibitory action on Purkinje cells was found to be narrow up to 60 days after birth. (4) These results concerning the dates of commencement of excitatory and inhibitory synaptic actions in the cerebellar cortex were compared with those of synaptogenesis studied morphologically, and some implications of the dates in the functional development of the cerebellar cortex were discussed.

Animals↗
PubMed1975

Electrophysiological studies of the projections from the parietal association area to the cerebellar cortex.

1. Responses evoked in the cerebellar cortex by stimulation of the parietal association cortex (rostral portions of the middle suprasylvian gyrus) were recorded and analysed in cats, and were compared with those by stimulation of the motor cortex (anterior sigmoid gyrus). 2. The parietal stimulation elicited early mossy fibre and late climbing fibre responses in the cerebellar cortex. The mossy fibre responses appeared at a latency of 2.0--2.5 msec and predominantly in the lateral (hemispherical) part of the contralateral cerebellum (mainly crus I, crus II and paramedian lobules). Cutting of the inferior cerebellar peduncle produced little or no influence upon the mossy fibre responses, which suggests that the mossy fibre responses are mediated chiefly by the pontine nuclei. 3. The climbing fibre responses were recorded at a latency of 17--19 msec and markedly in the contralateral intermediate and medial parts of IV--VI lobules. The responses were easily sppressed by anaesthesia and depended on the conditions of experimental animals. The unstable appearance of the responses and their longer latencies than those of the climbing fibre responses due to stimulation of the motor cortex imply indirect pathways from the parietal association cortex to the inferior olive. 4. The predominant projection of the parietal-induced mossy fibre responses to the lateral part of the cerebellum was compared with the mossy fibre projection from the motor cortex and was discussed as an important component in the cerebrocerebellar loops.

Animals↗
PubMed1977

Mechanisms by which diazepam, muscimol, and other drugs change the content of cGMP in cerebellar cortex.

THE CEREBELLUM CONSISTS OF TWO PARTS: the cerebellar nuclei whose connections to the various parts of the central nervous system coordinate muscle movements, and the cerebellar cortex which exerts an inhibitory influence on the cerebellar nuclei through the release of gamma-aminobutyric acid (gammaAbu) from Purkinje cells. The activity of Purkinje cells is regulated by two excitatory inputs to the cerebellar cortex-the climbing and mossy fibers-and by a neuronal network within the cortex which inhibits the activity of Purkinje cells through the release of gammaAbu from interneurons. The net activity of Purkinje cells is related to their content of guanosine 3':5'-cyclic monophosphate (cGMP) which increases or decreases according to changes in the activity of climbing and mossy fibers as well as to changes in the activation of gammaAbu receptors. When these receptors are activated, the cGMP of Purkinje cells decreases; when they are inhibited, the cGMP increases.The cGMP content of the cerebellar cortex is altered by drugs that change either the excitatory input of climbing or mossy fibers or the inhibitory input mediated by the activation of gammaAbu receptors. Mechanisms by which various drugs alter the cerebellar content of cGMP were investigated. By using various experimental designs, it was shown that diazepam and muscimol lowered the cGMP content by activating gammaAbu receptors. In contrast, morphine and haloperidol lowered the cerebellar cortex cGMP by decreasing the excitation of mossy fibers whereas harmaline increased the cGMP by increasing the excitation of the climbing fibers.

Alkaloids↗
PubMed1975

Mode of distribution of aminergic fibers in the cerebellar cortex of the chicken.

The cerebellar cortex of adult hens contains a dense plexus of thin varicose nerve fibers which display a formaldehyde-induced green fluorescence. This plexus is not distributed at random in the cortical layers. Within the granular layer the plexus forms a netlike pattern. The fiber branches, which have numerous varicosities, are predominantly oriented in the traverse plane of the folium. In the molecular layer the fluorescent plexus shows some variations in the convex, flat and concave portions of the folia. Many of the fluorescent branches are oriented parallel to the course of the folium. They arise from a T-division of radially oriented axons resembling parallel fibers in Golgi sections. The meshes of the fluorescent plexus in the granular layer measure 10-60 mu. In the molecular layer (top of the folia) there are about 30 fluorescent fibers per 100 mu2. The fluorescent fibers originate from the locus coeruleus and form a rostral and a caudal bundle in the cerebellar peduncle. The mode of distribution of the fluorescent fibers in the cortical layers seems to depend on the organization of the innervated tissue. Light microscopy suggests that the aminergic fibers innervate more than one class of cerebellar neurons.

Amines↗
PubMed1992

Actions of acetylcholinesterase in the guinea-pig cerebellar cortex in vitro.

Acetylcholinesterase is released in a calcium-dependent manner when afferents of the cerebellar cortex are stimulated. Since cholinergic transmission is probably insignificant in the cerebellar cortex, the esterase itself might serve as a transmitter or modulator. Therefore, the effect of acetylcholinesterase in the cerebellum was investigated in slices of guinea-pig cerebella during intracellular recording from Purkinje cell somata or dendrites. Addition of acetylcholinesterase (20 U/ml) to the superfusion medium did not change the membrane potential or the input resistance of the Purkinje cells. Thus, esterase does not act like a classical transmitter. The threshold for Na+ spikes generated by intracellular current injection was unaffected, but the threshold for Ca2+ spikes was increased. This increase was abolished by tetrodotoxin (1 microM). Furthermore, when Ca2+ currents were blocked by substituting Mn2+ for Ca2+ (2 mM) a decrease in a Na+ plateau potential was seen in the presence of esterase. The effect of acetylcholinesterase of Ca2+ spikes is therefore most likely due to a reduction of the non-inactivating Na+ current of the Purkinje cell membrane. When present this current contributes to activation of Ca2+ spikes in dendrites. Acetylcholinesterase also enhanced the response of Purkinje cells to the excitatory amino acids glutamate and aspartate thought to be transmitters in the cerebellar cortex. The responses became larger and faster in the presence of esterase. Responses to climbing fibre stimulation were also enhanced by acetylcholinesterase. The late part of this synaptic response was increased. The potentiation by esterase of responses of Purkinje cells to excitatory amino acids and to climbing fibre stimulation may be mediated through interference with transmitter uptake, because it was prevented by treatment with DL-2-amino-4-phosphonobutyric acid (0.5 mM) and di-hydrokainate (0.1 mM). None of the effects of esterase was due to hydrolysis of acetylcholine because irreversible inhibition of the catalytic site of the enzyme with soman did not prevent the actions. The observations were specific for acetylcholinesterase. Butyrylcholinesterase (20-40 U/ml) showed none of the effects. It is concluded that acetylcholinesterase in the cerebellar cortex seems to mediate a novel type of modulation by two separate mechanisms. Esterase reduces the tendency towards Ca2+ spike generation in Purkinje cells. Ca2+ spikes are followed by afterhyperpolarizations and in their absence firing of Na+ spikes at higher frequencies is possible. Secondly, there is an enhancement of the action of excitatory transmitters so that the extended operating range can be utilized.

Acetylcholinesterase↗
PubMed1977

Pharmacologically induced changes in the 3':5'-cyclic guanosine monophosphate content of rat cerebellar cortex: difference between apomorphine, haloperidol and harmaline.

Harmaline increases cerebellar 3':5'-cyclic guanosine monophosphate (cGMP) content in a dose-related manner; this increase is prevented by a pretreatment with 3-acetylpyridine (3-AP) (0.66 mmol/kg) which destroys climbing fibers and inhibits harmaline-induced tremor. The cerebellar cGMP content increases after isoniazid; this response remains unchanged in rats pretreated with 3-AP. Since isoniazid decreases cerebellar gamma-aminobuturic acid (GABA) levels, the increase in cGMP content might reflect a reduction in the availability of GABA at the level of postsynaptic receptors. Apomorphine (a dopamine receptor agonist) and haloperidol (a dopamine receptor blocker) increase or decrease the cGMP content of cerebellar cortex, respectively. Neither drug changes the guanylate cyclase activity of cerebellar homogenates; moreover their action on cerebellar cGMP content persists after 3-AP. Chloropromazine, like haloperidol, decreases the cerebellar cGMP content. The increase in cerebellar cGMP content elicited by apomorphine can be differentiated from that elicited by harmaline or isoniazid; presumably apomorphine indirectly activates mossy fibers. The decrease in cerebellar cGMP content elicited by haloperidol can be differentiated from that elicited by diazepam; perhaps haloperidol reduces the mossy fiber input to the cerebellum. We suggest that the cGMP content of cerebellar cortex fluctuates in response to changes in the afferent stimulatory input to the cerebellum; it increases when the activity of either climbing or mossy fibers is increased; it decreases when either of these two stimulatory inputs is reduced.

Alkaloids↗
PubMed1978

The myelination of the cerebellar cortex in the cat.

The myelination of the cerebellar cortex of the cat was investigated in 61 cats aged from 3 hrs post partum to two and a half years. The first myelinated fibers appear at the time of birth in the central medullary ray. Before the onset of myelination, all fibers reach a critical diameter of about 1 micrometer. About the 14th day of life the number of oligodendrocytes in the prospective while matter increases markedly. Thereafter, the oligodendrocytes invade the inner granular layer. It therefore seems that the myelination of the cerebellar cortex proceeds from the central medullary ray towards the granular layer. At the 60th day of postnatal life, most of the afferent and efferent fiber systems are myelinated. These findings are discussed in relation to the development of function and the maturation of the electrical activity of the cerebellar circuit.

Animals↗
PubMed1990

Learning causes synaptogenesis, whereas motor activity causes angiogenesis, in cerebellar cortex of adult rats.

The role of the cerebellar cortex in motor learning was investigated by comparing the paramedian lobule of adult rats given difficult acrobatic training to that of rats that had been given extensive physical exercise or had been inactive. The paramedian lobule is activated during limb movements used in both acrobatic training and physical exercise. Acrobatic animals had greater numbers of synapses per Purkinje cell than animals from the exercise or inactive groups. No significant difference in synapse number or size between the exercised and inactive groups was found. This indicates that motor learning required of the acrobatic animals, and not repetitive use of synapses during physical exercise, generates new synapses in cerebellar cortex. In contrast, exercise animals had a greater density of blood vessels in the molecular layer than did either the acrobatic or inactive animals, suggesting that increased synaptic activity elicited compensatory angiogenesis.

Animals↗
PubMed1992

Serotoninergic fibres form dense synaptic contacts with Purkinje cells in the mouse cerebellar cortex--an immunohistochemical study.

The distribution of serotonin immunoreactivity in the mouse cerebellar cortex was studied using the indirect antibody peroxidase-antiperoxidase (PAP) technique of Sternberger (1979) on epoxy embedded semithin sections. The great majority of serotonin-positive afferents distribute throughout the Purkinje cell layer and form dense synaptic contacts with the somata of the Purkinje neurons. Only a sparse immunostaining of serotoninergic fibres could be detected at the granular cell and molecular layers. The microanatomical organization of the serotoninergic projections to the mouse cerebellar cortex is quite different from that observed in other animal species. These findings suggest that in the mouse cerebellar cortex, the Purkinje cell population represents the main target for serotoninergic afferents. Our histochemical data provide morphological support for a series of electrophysiological observations which indicate serotonin as a potential modulatory neurotransmitter for Purkinje cell firing activity.

Animals↗
PubMed1992

Expression of tenascin in the developing and adult cerebellar cortex.

Since tenascin may influence neuronal cell development, we studied its expression pattern using immunocytochemistry, in situ hybridization, Northern blot analysis, and immunochemistry in the developing and adult mouse cerebellar cortex. Tenascin immunoreactivity was detectable in all layers of the developing cerebellar cortex. In the external granular layer, only the radially oriented processes of Golgi epithelial cells were immunoreactive, whereas the densely packed cell bodies were immunonegative. Tenascin was hardly detectable at contact sites between migrating granule cells and processes of Golgi epithelial cells. Axons of granule cells in the molecular layer were immunoreactive, whereas their cell bodies in the internal granular layer lacked detectable levels of tenascin. By in situ hybridization, only Golgi epithelial cells and astrocytes of the internal granular layer and prospective white matter, but not nerve cells, could be shown to synthesize detectable levels of tenascin mRNA in the developing mouse cerebellar cortex. Thus, tenascin in the cerebellar cortex seems to be a glia-derived molecule that becomes adsorbed to neuronal surfaces in a topographically restricted pattern in situ. Levels of tenascin protein and mRNA decreased significantly with increasing age. In the adult, tenascin immunoreactivity was weak and mainly restricted to the molecular layer and tenascin mRNA was confined to Golgi epithelial cells, indicative for a functional heterogeneity in differentiated cerebellar astrocytes. Quantitative immunoblot analysis revealed that the 225 and 240 kDa components of tenascin were developmentally downregulated at a faster rate than the 190 and 200 kDa components, corresponding to the faster downregulation of the 8 kilobase (kb) mRNA species compared to the 6 kb mRNA species as revealed by Northern blot analysis. These observations indicate a differentially regulated expression of the tenascin components. We hypothesize that glia-derived tenascin modifies the functional properties of nerve cell surfaces and that tenascin is involved in such different morphogenetic events as neurite growth and oligodendrocyte distribution.

Animals↗
PubMed1992

[The cerebellar cortex in sudden infant death].

The author examined the cerebellar cortex in 190 post-mortem examinations, incl. 79 sudden infant deaths and 56 infants under one year with a clearly defined cause of death, six sudden deaths of toddlers and 8 toddlers with other causes of death and 41 death of subjects aged 17 months to 66 years who died from violent deaths. In 50 sudden infant deaths the authors observed a persistence of the external granular layer, as compared with a control group, in 29 infants no difference was detected. The external granular layer persisted in a 16-month-old toddler who died suddenly and in a 22-month old toddler who was drowned. A persisting external granular layer may be a supporting sign of retarded development of the cerebellar cortex in sudden infant deaths.

Adolescent↗
PubMed1992

The physiological effects of serotonin are mediated by the 5HT1A receptor in the cat's cerebellar cortex.

Serotonin is present in a fine beaded plexus in the cerebellar cortex of several mammalian species. In the cat, serotoninergic afferents arise from neurons located within the lateral, paramedian and peri-olivary reticular nuclei (Kerr and Bishop, J. Comp. Neurol., 304 (1991) 502-515). In addition to serotoninergic afferents, these same nuclei also contain a separate population of neurons that give rise to mossy fibers to the cerebellar cortex. Physiological studies have shown that mossy fibers are excitatory to their target neurons. The intent of the present study was to determine the physiological effects of serotonin in the cat's cerebellum in an in vivo preparation and to identify the receptor(s) that mediate the observed responses. Iontophoretic application of serotonin (5HT) onto Purkinje cells reduces the spontaneous firing rate of all cells tested (n = 12). Serotonin also blocks the excitatory effects elicited by the application of aspartate in 17 of 19 units tested and of glutamate (n = 62) in all cases. In addition, 5HT potentiated the inhibitory action of GABA (n = 12). Iontophoretic application of the 5HT1A agonists, 8-OH-DPAT and ipsapirone, mimic the suppressive action of serotonin in a dose-dependent manner. This response, as well as the 5HT mediated suppression are blocked by the application of spiperone, a 5HT1A antagonist. Compounds selective for the 5HT1C,2 and 3 receptors are physiologically ineffective. The present data are in partial agreement with previous studies in the rat's cerebellar cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗