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Results for “CEREBELLAR CORTEX”

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At least 1,063 records · Page 59Linked to original sources
PubMed1983

Experimental phenylketonuria: effect of phenylacetate intoxication on number of synapses in the cerebellar cortex of the rat.

In experimental phenylketonuria, induced in the rat by exposure to phenylacetate during the first 21 days of life, there was a significant reduction of boutons, a decrease of an average of 25% in the whole cerebellar molecular layer. Both the density of synaptic profiles per square unit and the number of synapses per unit volume were decreased in the phenylacetate-treated rat as compared to the age-matched control. Neuronal density was unaffected. Results are interpreted to show a deficit of synapses per neuron, probably due to a decrease in synaptic formation in phenylacetate-induced phenylketonuria. Undernutrition was eliminated as a contributing factor.

Animals↗
PubMed1984

Presynaptic inclusions in mossy fibre terminals of the cerebellar cortex following long-term undernutrition in adult rats.

Past work on the C.N.S. of nutritionally deprived immature rats shows widespread structural and functional alterations that were not found in nutritionally deprived adults. In the present work we studied cerebellar mossy fibre terminals of adult rats, given a 8% casein diet for periods of 6, 12 and 18 months. After 12 months of the diet, mossy fibre terminals presented a large number of spherical or disc-shaped membrane-free inclusions herein referred to as presynaptic inclusions, with diameters up to 1.3 micron and formed by fine-textured subunits, compacted into 3 nm strands. This material is an extension of the cytoplasmic network of the terminal. No special relationship was observed with the active zones; synaptic vesicles found in the proximity or embedded in these inclusions were often of the flat type, whereas those close to the active zones always appeared spherical. These results show that even in adult rats synaptic terminals are areas sensitive to protein deprivation.

Animals↗
PubMed1990

Brain stem regions mediating the cardiovascular responses elicited from the posterior cerebellar cortex in the rabbit.

1. In this study we have examined the roles of the lateral parabrachial nucleus (lateral PBN) and nucleus tractus solitarius (NTS) as sites mediating the circulatory responses evoked from lobule IX b of the posterior cerebellar vermis in the decerebrate and anaesthetized decerebrate rabbit. Microinjection of either kainic acid or bicuculline into the lateral PBN and NTS was undertaken to assess the importance of neurones and GABAergic mechanisms, respectively, in expressing the cardiovascular responses evoked from lobule IX b. 2. In both the decerebrate and anaesthetized decerebrate rabbit activation of neurones within the lateral PBN with a microinjection of glutamate elicited tachycardia and a pressor response together with an increase in renal sympathetic nerve discharge and vasoconstriction in the hindlimb. A microinjection of GABA into the lateral PBN evoked an opposite pattern of response. Chemical lesioning of neurones within the rostral region of the lateral PBN or pharmacological blockade of GABAA receptor, abolished or significantly attenuated the cardiovascular response (bradycardia/depressor effect) evoked from lobule IX b in the anaesthetized decerebrate rabbit. 3. In the decerebrate animal the tachycardia/pressor response elicited from lobule IX b was suppressed when either kainic acid or bicuculline was microinjected into the caudal division of the lateral PBN. 4. A bradycardia, depressor response, an abolition of on-going renal nerve activity and vasodilatation in the femoral bed were evoked by activating neurones within a restricted region of the NTS with glutamate in the decerebrate and anaesthetized decerebrate rabbit. A microinjection of GABA into the NTS produced a qualitatively opposite pattern of response. The bradycardia/depressor response evoked from lobule IX b in the anaesthetized decerebrate rabbit was not altered significantly following a microinjection of either kainic acid or bicuculline into the ipsilateral NTS. However, in the decerebrate preparation following a microinjection of bicuculline into the ipsilateral NTS the tachycardia/pressor response evoked from IX b was either abolished or in many cases reversed to the pattern of response seen in the anaesthetized decerebrate rabbit. 5. The present experiments provide evidence for two functionally distinct pathways from the cardiovascular region of lobule IX b to the lateral PBN.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

[Synaptic localization of 5'-nucleotidase activity in the cerebellar cortex in adult rats irradiated by X rays after birth].

5'-nucleotidase cytochemistry was performed in the cerebellum of adult rats exposed previously to a single postnatal X-irradiation which maintains until adulthood the normally transient multiple innervation of cerebellar Purkinje cells by climbing fibers. 5'-nucleotidase activity persists in climbing fiber synapses and other asymmetrical synapses while it is transient during normal development. Therefore, in the X-irradiated rat, an immature stage of the excitatory synapses persists which, for the climbing fibers, coïncides with or precedes their involution during normal development.

5'-Nucleotidase↗
PubMed2001

Dynamic modulation of mossy fiber system throughput by inferior olive synchrony: a multielectrode study of cerebellar cortex activated by motor cortex.

We investigated the effects of climbing fiber synchrony on the temporal dynamics of mossy fiber system throughput in populations of cerebellar Purkinje cells (PCs). A multielectrode technique was used in ketamine-anesthetized rats that allowed both complex and simple spikes (CSs and SSs) to be recorded from multiple PCs simultaneously in lobule crus IIa. Stimulation of the tongue area of the primary motor cortex (TM1) was used to evoke cerebro-cerebellar interaction. At the single PC level, robust short-term interactions of CSs and SSs were observed after TM1 stimulation that typically consisted of an immediate depression and subsequent enhancement of SS firing after the occurrence of a CS. Such modulations of SS rate in a given PC were as robustly correlated to the CSs of simultaneously recorded PCs as they were to the CS on its own membrane-and did not require a CS on its own membrane-indicating a network basis for the interaction. Analyses of simultaneously recorded PCs using the normalized joint perievent time histogram demonstrated that CS and SS firing were dynamically correlated after TM1 stimulation in a manner that indicated strong control of mossy fiber system throughput by CS synchrony. For < or =300 ms after TM1 stimulation, most PCs showed episodic modulations in SS rate that appeared to be entrained by the population rhythm of climbing fiber synchrony. SS rhythmicity also was modulated dynamically by CSs, such that it was depressed by CSs and facilitated by their absence. Like the modulations in SS rate, a given PC's modulation in SS rhythmicity did not require it to fire a CS but was, on those instances, equally correlated to the synchronous CSs of other PCs. The data indicate that the climbing fiber system controls the temporal dynamics of SS firing in populations of PCs by using synchrony to engage intracerebellar circuitry and modulate mossy fiber system throughput.

Action Potentials↗
PubMed1998

Distinct modes of neuronal migration in different domains of developing cerebellar cortex.

As postmitotic neurons migrate to their final destinations, they encounter different cellular microenvironments, but functional responses of migrating neurons to changes in local environmental cues have not been examined. In the present study, we used a confocal microscope on acute cerebellar slice preparations to examine real-time changes in the shape of granule cells, as well as the mode and rate of their migration as they transit different microenvironments. The rate of granule cell movement is fastest in the molecular layer, whereas their elongated somata and long leading processes remain in close contact with Bergmann glial fibers. Cell movement is slowest in the Purkinje cell layer after granule cells detach from the surface of Bergmann glia and the somata become transiently round, whereas the leading processes considerably shorten. Surprisingly, after entering the internal granular layer, granule cells re-extend both their somata and leading processes as they resume rapid movement independent of Bergmann glial fibers. In this last phase of migration, described here for the first time, most granule cells move radially for >100 micron (a distance comparable to that observed in the molecular layer) until they reach the deep strata of the internal granular layer, where they become rounded again and form synaptic contacts with mossy fiber terminals. These observations reveal that migrating neurons alter their shape, rate, and mode of movement in response to local environmental cues and open the possibility for testing the role of signaling molecules in cerebellar neurogenesis.

Aging↗
PubMedDate not supplied

[Atrophy of the granular layer of the cerebellar cortex in patients with nonlymphoblastic leukemia treated with cytosine arabinoside].

The reported analysis comprised 81 patients dying of acute non-lymphoblastic leukaemia type M1, M2, M4 and blastic crises in chronic myelocytic leukaemia. It was observed that the number of cases of cerebellar granular layer atrophy rose markedly in the years 1984-1990 as compared with 1976-1983 (45.4% vs 16.2%). It is suggested that this was due to the introduction of cytostatic treatment schedules with higher doses of cytosine arabinoside (ARAC), especially TAD (6-thioguanine, ARAC, daunorubicin). Cerebellar granular layer atrophy seems to be dependent rather on the cumulative dose of ARAC and not on a single high dose of that drug.

Adolescent↗