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

Pichitpornchai, Chailerd; Rawson, John A; Rees, Sandra

doi:10.1002/cne.903420205

Cited by 163 publications

(115 citation statements)

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“…7 D, E). These fibers differed from the parallel fibers (Harvey and Napper, 1991) by their larger diameter (Ͼ1 m) and may correspond to a previously identified minor population of large fibers running parallel to the parallel fibers in the lower molecular layer (Pichitpornchai et al, 1994). The thickest portion of these axons could easily be followed for hundreds of micrometers (Fig.…”

Section: Organization Of the Lugaro Cell Axonal Plexusmentioning

confidence: 81%

“…Our observations indicate that their length in rat is also in the millimeter range. A more precise value of 2 mm (half the length of the parallel fibers) can be taken from Pichitpornchai et al (1994), who found a small subpopulation of thick fibers running parallel to the parallel fibers in the lower third of the molecular layer and emitting short lateral branches, as reported by Fox (1959) for Lugaro cell axons.…”

Section: Organization Of the Golgi Cell-lugaro Cell Connectionmentioning

confidence: 99%

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Serotonin-Driven Long-Range Inhibitory Connections in the Cerebellar Cortex

2000

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Disturbances of the serotoninergic neuromodulation in the cerebellar cortex have been involved in several types of ataxia, but the physiological action of serotonin in this structure remains poorly understood. We report that in slices of the rat cerebellar vermis, serotonin triggers the firing of an inhibitory interneuron presynaptic to Golgi cells. The Lugaro cell, a neglected interneuronal type, satisfies the expected criteria for this input, whereas basket cells, stellate cells, or Golgi cells do not. Lugaro cells are selectively excited by serotonin, and their firing behavior (sustained steady frequency in the 5-15 Hz range) resembles the pattern of occurrence of serotonin-evoked IPSCs in Golgi cells. Immunohistochemical stainings and single cell reconstructions show that Lugaro cell axons form a parasagittal plexus but also extend long transverse branches that run parallel to the parallel fibers and are partly myelinated. Electrophysiological data suggest that these transverse axons participate in synaptic contacts of the Lugaro cells with Golgi cells, and we calculated that in the intact cerebellum a given Lugaro cell contacts Ͼ100 Golgi cells. Serotonin modulation of Lugaro cells may constitute an intracortical switch involved in information patterning at the level of Golgi cells and granule cells populations, and particularly in synchronizations recorded along the transverse axis in vivo.

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Section: Organization Of the Lugaro Cell Axonal Plexusmentioning

confidence: 81%

Section: Organization Of the Golgi Cell-lugaro Cell Connectionmentioning

confidence: 99%

Serotonin-Driven Long-Range Inhibitory Connections in the Cerebellar Cortex

2000

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“…Ascending axon synapses were activated with electrodes placed in the GC layer, 30 -100 m directly behind the PC soma. Ascending axons make ϳ30 synaptic contacts before forming parallel fibers (Pitchitpornchai et al, 1994). Because parallel fibers make on average only one or at most two synapses with a single PC (Harvey and Napper, 1991), then in this configuration, the likelihood of activating parallel fiber synapses is small.…”

Section: Methodsmentioning

confidence: 99%

Differential Susceptibility to Synaptic Plasticity Reveals a Functional Specialization of Ascending Axon and Parallel Fiber Synapses to Cerebellar Purkinje Cells

Sims

Hartell²

2006

J. Neurosci.

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Granule cell axons, via their parallel fibers, form synapses with Purkinje cells across large areas of the cerebellar cortex. Evidence for uniform transmission along parallel fibers to Purkinje cells is controversial, however, leading to speculation that the ascending axonal segment plays a dominant role in cerebellar processing. We have compared the relative susceptibilities of ascending axon and parallel fiber synaptic inputs to several forms of synaptic plasticity. We demonstrate that ascending axon synapses have a limited capability to undergo forms of long-term depression and potentiation compared with parallel fiber synapses. These results demonstrate that these two segments of the same axon play fundamentally different roles in cerebellar signaling, and, as such, the synapses formed between granule cells and Purkinje cells should not be treated as a homogenous population.

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“…Except for a few hundred synapses associated with the climbing fiber input, all the remaining excitatory synapses originate from granule cells (Llinas 1990) with the majority associated with the parallel fiber segment of the granule cell axon (Harvey and Napper 1991). Each parallel fiber extends for several millimeters in a direction orthogonal to the planar structure of the Purkinje cell dendrite (Harvey and Napper 1991;Pichitpornchai et al 1994). The size of this synaptic input and the strict geometrical relationship between the associated axon and the Purkinje cell dendrite has been a dominate influence on all structural theories of cerebellar function (for review, see Bower 2002).…”

Section: Parallel Fiber and Ascending Segment Synapsesmentioning

confidence: 99%

Background Synaptic Activity Modulates the Response of a Modeled Purkinje Cell to Paired Afferent Input

Santamarı́a¹,

Bower²

2005

Journal of Neurophysiology

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Santamaria, Fidel and James M. Bower. Background synaptic activity modulates the response of a modeled Purkinje cell to paired afferent input. J Neurophysiol 93: [237][238][239][240][241][242][243][244][245][246][247][248][249][250] 2005. First published August 11, 2004; doi:10.1152/jn.00458.2004. We studied the possible effects of background excitatory and inhibitory synaptic activity on Purkinje cell responses to paired pulse inputs using a morphologically and physiologically detailed compartmental model. Paired-pulse inputs were provided via synapses associated with the ascending segment of the granule cell axon in the presence of variable amounts of background synaptic input provided by parallel fibers and inhibitory interneurons. The results predict the amplitude and dynamics of the somatic and dendritic responses to paired ascending segment inputs are modulated by the level of background synaptic activity, the basal somatic firing rate of the Purkinje cell model does not indicate the type or degree of modulation, and the modulatory effects are mediated through dendritic calcium and calcium-activated potassium currents. These results have important consequences for the functional organization of cerebellar cortex as well as the more general issue of the modulatory as distinct from driving effects of synapses now also being considered in other regions of the mammalian brain including the cerebral cortex. I N T R O D U C T I O NIn recent years, there has been a continually growing interest in the interaction between the active electrical properties of neuronal dendrites and the responses of those dendrites to synaptic input (Chance et al. 2002;Euler and Denk 2001;Hausser and Mel 2003;Migliore and Shepherd 2002). Although neuronal dendrites have traditionally most often been modeled as spatial and temporal summing devices (see London and Segev 1999;Rall 1999), it is clear that the presence of active conductances in dendrites substantially affects how these structures integrate synaptic inputs (Cook and Johnston 1999;De Schutter and Bower 1994c;London and Segev 2001;Poirazi et al. 2003;Williams and Stuart 2002). In fact, model (Chance et al. 2002)-and experimental-based (Frick et al. 2004) studies of the functional consequences of active dendritic membranes are starting to raise questions about whether all synapses are fundamentally "driving" in nature. Specifically, it is now being suggested that some synapses might be more involved in regulating dendritic dynamics than in directly influencing the spiking output of neurons (Chance et al. 2002;De Schutter and Bower 1994b;Jaeger and Bower 1999;Jaeger et al. 1997;Rhodes and Llinas 2001;Santamaria et al. 2002;Sherman and Guillery 1998).The cerebellar Purkinje cell was one of the first mammalian neurons in which experimental studies demonstrated substantial voltage-dependent dendritic conductances (Llinas and Sugimori 1980). Using an articulated set of modeling and experimental studies, we have engaged in a series of experiments intended to better understand the f...

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

Cited by 163 publications

References 21 publications

Serotonin-Driven Long-Range Inhibitory Connections in the Cerebellar Cortex

Serotonin-Driven Long-Range Inhibitory Connections in the Cerebellar Cortex

Differential Susceptibility to Synaptic Plasticity Reveals a Functional Specialization of Ascending Axon and Parallel Fiber Synapses to Cerebellar Purkinje Cells

Background Synaptic Activity Modulates the Response of a Modeled Purkinje Cell to Paired Afferent Input

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