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Results for “CEREBELLAR CORTEX”

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At least 973 records · Page 54Linked to original sources
PubMed2006

Survival of interneurons and parallel fiber synapses in a cerebellar cortex deprived of Purkinje cells: studies in the double mutant mouse Grid2Lc/+;Bax(-/-).

The Lurcher mutation in the Grid2 gene causes the cell autonomous death of virtually all cerebellar Purkinje cells and the target-related death of 90% of the granule cells and 60-75% of the olivary neurons. Inactivation of Bax, a pro-apoptotic gene of the Bcl-2 family, in heterozygous Lurcher mutants (Grid2Lc/+) rescues approximately 60% of the granule cells, but does not rescue Purkinje or olivary neurons. Given the larger size of the cerebellar molecular layer in Grid2Lc/+;Bax(-/-) double mutants compared to Grid2Lc/+ mutants, we analyzed the survival of the stellate and basket interneurons as well as the synaptic connectivity of parallel fibers originating from the surviving granule cells in the absence of their Purkinje cell targets in the Grid2Lc/+;Bax(-/-) cerebellum. Quantification showed a significantly higher density of interneurons ( approximately 60%) in the molecular layer of the Grid2Lc/+;Bax(-/-) mice compared to Grid2Lc/+, suggesting that interneurons are subject to a BAX-dependent target-related death in the Lurcher mutants. Furthermore, electron microscopy showed the normal ultrastructural aspect of a number of parallel fibers in the molecular layer of the Grid2Lc/+; Bax(-/-) double mutant mice and preserved their numerous synaptic contacts on interneurons, suggesting that interneurons could play a trophic role for axon terminals of surviving granule cells. Finally, parallel fibers varicosities in the double mutant established "pseudo-synapses" on glia as well as displayed autophagic profiles, suggesting that the connections established by the parallel fibers in the absence of their Purkinje cell targets were subject to a high turnover involving autophagy.

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PubMed2004

Developmental changes in eyeblink conditioning and simple spike activity in the cerebellar cortex.

The activity of neurons in the cerebellum exhibits learning-related changes during eyeblink conditioning in adult mammals. The induction and preservation of learning-related changes in cerebellar neuronal activity in developing rats may be affected by the level of maturity in cerebellar feedback to its brainstem afferents, including the inferior olive. Developmental changes in cerebellar plasticity were examined by recording the activity of Purkinje cells in eye regions of cerebellar cortical lobule HVI (lobulus simplex) in infant rats during eyeblink conditioning. The percentage and amplitude of eyeblink conditioned responses increased as a function of age. Analyses of Purkinje cell simple spike activity revealed developmental increases in the number of units that exhibited stimulus-evoked and learning-related changes in activity. Moreover, the magnitude of these changes exhibited a substantial age-related increase. The results support the view that the emergence of learning-specific cerebellar plasticity and the ontogeny of eyeblink conditioning are influenced by developmental changes in the synaptic interactions within brainstem-cerebellum circuits.

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PubMed1999

GAT-1 developmental expression in the rat cerebellar cortex: basket and pinceau formation.

In view of the key role exerted by neurotransmitter transporters in the synaptic transmission, the expression of GABA transporter GAT-1 was analysed during cerebellar development, when relevant processes of synapse maturation take place. GAT-1-immunoreactive (IR) structures started to be detected on PD 8-9, at the low molecular and Purkinje cell layer, coincident with the onset of functional inhibitory synapses on Purkinje neurons. By PD 18, GAT-1-IR structures completely ensheathed the Purkinje cell somata thus outlining the characteristic perisomatic formation, whereas GAT-1 wrapping on the axon initial segment started to be detected only at PD 15, and the mature form of the pinceau was fully developed from PD 23 on. These results, when compared with the functional maturation of the GABAergic input to Purkinje cells, indicate that GAT-1 may play a significant role in the differentiation of basket interneuron-Purkinje cell circuit.

Animals↗
PubMed1999

GAT-1 developmental expression in the rat cerebellar cortex: basket and pinceau formation.

In view of the key role exerted by neurotransmitter transporters in the synaptic transmission, the expression of GABA transporter GAT-1 was analysed during cerebellar development, when relevant processes of synapse maturation take place. GAT-1-immunoreactive (IR) structures started to be detected on PD 8-9, at the low molecular and Purkinje cell layer, coincident with the onset of functional inhibitory synapses on Purkinje neurons. By PD 18, GAT-1-IR structures completely ensheathed the Purkinje cell somata thus outlining the characteristic perisomatic formation, whereas GAT-1 wrapping on the axon initial segment started to be detected only at PD 15, and the mature form of the pinceau was fully developed from PD 23 on. These results, when compared with the functional maturation of the GABAergic input to Purkinje cells, indicate that GAT-1 may play a significant role in the differentiation of basket interneuron-Purkinje cell circuit.

Animals↗
PubMed1993

Synaptic plasticity in the cerebellar cortex and its role in motor learning.

Synaptic plasticity plays a role in the learning capability of brain tissues. Long-term depression (LTD) of parallel fiber synapses in cerebellar Purkinje cells occurs when these synapses are activated in conjunction with climbing fiber synapses. Signal transduction mechanisms underlying LTD have recently been investigated extensively. It has also become apparent that climbing fiber signals encode errors in the motor performance of an animal. It is therefore hypothesized that learning proceeds in cerebellar tissues in such a way that error signals of climbing fibers act to depress by LTD those parallel fiber synapses responsible for the errors. The cerebellum contains a large number of corticonuclear microcomplexes. Each microcomplex is connected to an extracerebellar system and is presumed to endow the system with learning capability. The hypothesis accounts for the adaptation of the vestibuloocular reflex and probably also for other forms of motor and cognitive learning.

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