Sodium Imaging of Climbing Fiber Innervation Fields in Developing Mouse Purkinje Cells

2003 ◽  
Vol 89 (5) ◽  
pp. 2555-2563 ◽  
Author(s):  
Bibiana Scelfo ◽  
Piergiorgio Strata ◽  
Thomas Knöpfel

Maturation of specific neuronal connections in the mature nervous system includes elimination of redundant synapses formed earlier during development. In the cerebellum of adult animals, each Purkinje cell (PC) is innervated by a single climbing fiber (CF). In early postnatal development each PC is innervated by multiple CFs and elimination of synapses formed by supernumerary CFs occurs until monoinnervation is established at around postnatal day 20 (P20) in mice. It is not clear whether multiple CFs, or only a single CF, translocate from the cell body of immature PCs to the developing dendrite and, in case several CFs translocate, whether they share or segregate their innervation fields. To localize CF innervation fields, we imaged changes in postsynaptic sodium concentration resulting from CF-mediated postsynaptic currents. We found that more than one CF translocates from an innervation field on the cell body of the PC to the developing dendrite and that these CFs share rather than segregate their innervation fields. We concluded that both the soma and the proximal dendrite of the PC are territories of competition for the developing CFs and that the overlapping of their termination fields may be the prerequisite for a local process of elimination of all but one CF, as previously demonstrated in the developing neuromuscular junction.

1997 ◽  
Vol 77 (1) ◽  
pp. 145-152 ◽  
Author(s):  
Joseph C. Callaway ◽  
William N. Ross

Callaway, Joseph C. and William N. Ross. Spatial distribution of synaptically activated sodium concentration changes in cerebellar Purkinje neurons. J. Neurophysiol. 77: 145–152, 1997. The spatial distribution of Na+-dependent events in guinea pig Purkinje cells was studied with a combination of high-speed imaging and simultaneous intracellular recording. Individual Purkinje cells in sagittal cerebellar slices were loaded with either fura-2 or the Na+ indicator sodium binding benzofuran isophthalate (SBFI) with sharp electrodes or patch electrodes on the soma or dendrites. [Na+]i changes were detected in response to climbing fiber and parallel fiber stimulation. These changes were located both at the anatomically expected sites of synaptic contact in the dendrites and in the somatic region. The variation in time course of these [Na+]i changes in different locations implies that Na+ enters at the synapse and diffuses rapidly to locations of lower initial [Na+]i. The synaptically activated somatic [Na+]i changes probably reflect Na+ entry through voltage-sensitive Na+ channels because they were detected only when regenerative potentials were recorded in the soma. [Na+]i changes in response to antidromically or intrasomatically evoked Na+ action potentials also were confined to the cell body. These observations are in agreement with other evidence that Na+ spikes are generated in the somatic region of the Purkinje neuron and spread passively into the dendrites. Plateau potentials, evoked by depolarizing pulses to the soma or dendrites, caused [Na+]i changes only in the soma, indicating that the noninactivating Na+ channels contributing to this potential also were concentrated in this region. The climbing fiber-activated [Na+]i changes were blocked by the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione, indicating that these changes were not due to direct stimulation of the Purkinje neuron or activation of metabotropic receptors. Direct depolarization of the soma or dendrites never caused dendritic [Na+]i increases, suggesting that the climbing fiber-activated [Na+]i changes in the dendrites are due to Na+ entry through ligand-gated channels. A climbing fiber-like regenerative potential could be recorded in the soma after anode break stimulation, parallel fiber activation, or depolarizing pulses to the soma. The [Na+]i changes evoked by all of these potentials were confined to the cell body region of the Purkinje cell. [Ca2+]i changes in the dendrites evoked by the anode break potential were small relative to climbing fiber-activated changes, suggesting that a Ca2+ spike was not evoked by this response. The anode break and directly responses were blocked by tetrodotoxin. These results suggest that the somatically recorded climbing fiber response is predominantly a Na+-dependent event, consisting of a few fast action potentials and a slower regenerative response activating the same channels as the Na+ plateau potential.


2010 ◽  
Vol 68 ◽  
pp. e37-e38
Author(s):  
Kouichi Hashimoto ◽  
Mika Tsujita ◽  
Kazuo Kitamura ◽  
Taisuke Miyazaki ◽  
Maya Yamazaki ◽  
...  

2019 ◽  
Author(s):  
Alyssa Michelle Wilson ◽  
Richard Schalek ◽  
Adi Suissa-Peleg ◽  
Thouis Ray Jones ◽  
Seymour Knowles-Barley ◽  
...  

SUMMARYDuring postnatal development, cerebellar climbing fibers strongly innervate a subset of their original Purkinje cell targets and eliminate their connections from the rest. In the adult, each climbing fiber innervates a small number of Purkinje cells and each Purkinje cell is innervated by a single climbing fiber. To get insight about the processes responsible for this remapping, we reconstructed serial electron microscopy datasets from mice during the first postnatal week. In contrast to adult connectivity, individual neonatal climbing fibers innervate many nearby Purkinje cells, and multiple climbing fibers innervate each Purkinje cell. Between postnatal days 3 and 7, Purkinje cells retract long dendrites and grow many proximal dendritic processes. On this changing landscape, individual climbing fibers selectively add many synapses to a subset of Purkinje cell targets in a positive-feedback manner, without pruning synapses from other Purkinje cells. The active zone sizes of synapses associated with powerful versus weak inputs are indistinguishable. These results show that changes in synapse number rather than synapse size are the predominant form of early developmental plasticity. Finally, although multiple climbing fibers innervate each Purkinje cell in early postnatal development, the number of climbing fibers and Purkinje cells in a local cerebellar region nearly match. Thus, initial over-innervation of Purkinje cells by climbing fibers is economical, in that the number of axons entering a region is enough to assure that each axon ends up with a postsynaptic target, and that none branched there in vain.HIGHLIGHTSDeveloping climbing fibers establish synapses on many neighboring Purkinje cells unlike the sparse pattern of innervation in later lifeClimbing fibers add many synapses onto a few of their Purkinje targets before the pruning stage in a rich-get-richer type processThe synapse sizes of strengthened and weakened climbing fiber inputs are indistinguishable.Exuberant branching of climbing fiber axons in early postnatal life appears to be economical because the numbers of axons and Purkinje cells in a local region match, ensuring that each axon can establish a long-lasting connection thereBLURBHigh-resolution serial electron microscopy reconstructions reveal that climbing fiber-Purkinje cell synaptic refinement in the developing cerebellum begins with significant synapse addition. Climbing fibers focus their synapses onto a smaller number of Purkinje cells by selectively adding synapses onto some target cells. All axons that project to a region in development play a role in the final connectivity.


eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Farzaneh Najafi ◽  
Andrea Giovannucci ◽  
Samuel S-H Wang ◽  
Javier F Medina

The climbing fiber input to Purkinje cells acts as a teaching signal by triggering a massive influx of dendritic calcium that marks the occurrence of instructive stimuli during cerebellar learning. Here, we challenge the view that these calcium spikes are all-or-none and only signal whether the instructive stimulus has occurred, without providing parametric information about its features. We imaged ensembles of Purkinje cell dendrites in awake mice and measured their calcium responses to periocular airpuffs that serve as instructive stimuli during cerebellar-dependent eyeblink conditioning. Information about airpuff duration and pressure was encoded probabilistically across repeated trials, and in two additional signals in single trials: the synchrony of calcium spikes in the Purkinje cell population, and the amplitude of the calcium spikes, which was modulated by a non-climbing fiber pathway. These results indicate that calcium-based teaching signals in Purkinje cells contain analog information that encodes the strength of instructive stimuli trial-by-trial.


2007 ◽  
Vol 97 (4) ◽  
pp. 2590-2604 ◽  
Author(s):  
Bruce E. McKay ◽  
Jordan D. T. Engbers ◽  
W. Hamish Mehaffey ◽  
Grant R. J. Gordon ◽  
Michael L. Molineux ◽  
...  

The contribution of Purkinje cells to cerebellar motor coordination and learning is determined in part by the chronic and acute effects of climbing fiber (CF) afferents. Whereas the chronic effects of CF discharge, such as the depression of conjunctive parallel fiber (PF) inputs, are well established, the acute cellular functions of CF discharge remain incompletely understood. In rat cerebellar slices, we show that CF discharge presented at physiological frequencies substantially modifies the frequency and pattern of Purkinje cell spike output in vitro. Repetitive CF discharge converts a spontaneous trimodal pattern of output characteristic of Purkinje cells in vitro to a more naturalistic nonbursting pattern consisting of spike trains interrupted by short CF-evoked pauses or longer pauses associated with state transitions. All effects of CF discharge could be reproduced in the presence of synaptic blockers by using current injections to simulate complex spike depolarizations, revealing that CF-evoked changes in Purkinje cell output can occur independently of network activation. Rather postsynaptic changes are sufficient to account for the CF-evoked block of trimodal activity and include at least the activation of Ca2+-dependent K+ channels. Furthermore by controlling the frequency of Purkinje cell spike output over three discrete firing levels, CF discharge modulates the gain of Purkinje cell responsiveness to PF inputs in vitro through postsynaptic mechanisms triggered by the complex spike depolarization. The ability for CF discharge to acutely modulate diverse aspects of Purkinje cell output provides important insights into the probable cellular factors contributing to motor disturbances following CF denervation.


1997 ◽  
Vol 78 (6) ◽  
pp. 3083-3094 ◽  
Author(s):  
H. Fushiki ◽  
N. H. Barmack

Fushiki, H. and N. H. Barmack. Topography and reciprocal activity of cerebellar Purkinje cells in the uvula-nodulus modulated by vestibular stimulation. J. Neurophysiol. 78: 3083–3094, 1997. In the rabbit uvula-nodulus, vestibular and optokinetic information is mapped onto parasagittal zones by climbing fibers. These zones are related functionally to different pairs of vertical semicircular canals, otolithic inputs and horizontal optokinetic inputs. Vestibular stimulation restricted to one of these zones modulates climbing fiber responses (CFRs). Within each of these zones, simple spikes (SSs) are modulated reciprocally with CFRs. In rabbits anesthetized with chloralose-urethan, we have used vestibular and optokinetic stimulation to evoke CFRs within a parasagittal zone while recording from Purkinje cells in adjacent zones. We have examined whether the CFRs evoked by vestibular stimulation in one zone influence the SSs of an adjacent zone. CFRs and SSs were recorded during roll vestibular stimulation. The orientation of the head of the rabbit with respect to the axis of rotation was varied systematically so that a climbing fiber null plane could be determined. This null plane was the orientation of the head about the vertical axis at which no modulation of the CFR was observed during rotation about the longitudinal axis of the vestibular rate table. In the left uvula-nodulus, a medial sagittal strip extending through all the folia contained Purkinje cells with CFRs that had optimal planes of stimulation coplanar with the left posterior-right anterior semicircular canals (LPC-RAC). Lateral to this strip was a strip of Purkinje cells with CFRs that were characterized by optimal planes corresponding to stimulation of the left anterior-right posterior semicircular canals (LAC-RPC). SSs in Purkinje cells were modulated out of phase with CFRs from the same Purkinje cell. The depth of modulation of both CFRs and SSs was reduced during rotation in the climbing fiber “null plane”. The depth of modulation of SSs was greatest when recorded from Purkinje cells located at the center of semicircular canal-related strip. We observed that 1) all folia of the uvula-nodulus receive vestibular climbing fiber inputs; 2) these climbing fiber inputs convey information from the vertical semicircular canals and otoliths but not the horizontal semicircular canals; 3) CFRs evoked in a particular sagittal zone do not influence SSs in adjacent zones; 4) modulation of a CFRs in a particular Purkinje cell can occur without modulation of SSs in the same Purkinje cell, although modulation of SSs was not observed in the absence of CFR modulation; and 5) modulation of SSs sometimes preceded that of CFRs in the same cell, implying that interneuronal pathways may contribute to SS modulation. Climbing fiber-driven Golgi cells, the inhibitory axon terminals of which end on granule cell dendrites in the classic glomerular synapse, may provide this interneuronal mechanism.


1983 ◽  
Vol 50 (1) ◽  
pp. 205-219 ◽  
Author(s):  
T. J. Ebner ◽  
Q. X. Yu ◽  
J. R. Bloedel

These experiments were designed to test the hypothesis that climbing fiber inputs evoked by a peripheral stimulus increase the responsiveness of Purkinje cells to mossy fiber inputs. This hypothesis was based on a previous series of observations demonstrating that spontaneous climbing fiber inputs are associated with an accentuation of the Purkinje cell responses to subsequent mossy fiber inputs (10, 12). Furthermore, short-term nonpersistent interactions between climbing and mossy fiber inputs have been an important aspect of many theories of cerebellar function (5, 7, 8, 12, 36). Extracellular unitary recordings were made from Purkinje cells in lobule V of decerebrate, unanesthetized cats. To activate mossy and climbing fiber inputs, the forepaw was passively flexed by a Ling vibrator system. A data analysis was developed to sort the simple spike trials into two groups, based on the presence or absence of complex spikes activated by the stimulus. In addition, during those trials in which complex spikes were activated, the simple spike train was aligned on the occurrence of the complex spike. For each simple spike response to the forepaw input, the average firing rate during the response was compared to background both in those trials in which complex spikes were activated and in those in which they were not. The ratio of the response amplitudes in the histograms constructed from these two groups of trials permitted a quantification of the change in responsiveness when climbing fiber inputs were activated. The results show that both excitatory and inhibitory simple spike responses are accentuated when associated with the activation of a complex spike. Using an arbitrary level of a gain change ratio of 120% as indicating a significant modification, 64% of the response components analyzed increased their amplitude when climbing fiber input was present. Simple spike response components occurring prior to complex spike activation were usually not accentuated, although in a few cells the amplitude of this component of the response increased. In addition, in a small number of cells the occurrence of complex spikes was associated with a new simple spike component. For excitatory responses, the magnitude of the gain change ratio was shown to be inversely related to the amplitude of the simple spike response evoked by the mossy fiber inputs. The data obtained is consistent with the hypothesis that the climbing fiber input is associated with an increase in the responsiveness of Purkinje cells to mossy fiber inputs. The increased responsiveness occurs whether the simple spike modulation evoked by the peripheral stimulus is excitatory or inhibitory. The change in responsiveness is short term and nonpersistent. It is argued that the activation of climbing fiber inputs to the cerebellar cortex is associated with an increase in the gain of Purkinje cells to mossy fiber inputs activated by natural peripheral stimuli.


2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Lisanne J. van’t Sant ◽  
Joshua J. White ◽  
Jan H. J. Hoeijmakers ◽  
Wilbert P. Vermeij ◽  
Dick Jaarsma

AbstractFluorescent staining of newly transcribed RNA via metabolic labelling with 5-ethynyluridine (EU) and click chemistry enables visualisation of changes in transcription, such as in conditions of cellular stress. Here, we tested whether EU labelling can be used to examine transcription in vivo in mouse models of nervous system disorders. We show that injection of EU directly into the cerebellum results in reproducible labelling of newly transcribed RNA in cerebellar neurons and glia, with cell type-specific differences in relative labelling intensities, such as Purkinje cells exhibiting the highest levels. We also observed EU-labelling accumulating into cytoplasmic inclusions, indicating that EU, like other modified uridines, may introduce non-physiological properties in labelled RNAs. Additionally, we found that EU induces Purkinje cell degeneration nine days after EU injection, suggesting that EU incorporation not only results in abnormal RNA transcripts, but also eventually becomes neurotoxic in highly transcriptionally-active neurons. However, short post-injection intervals of EU labelling in both a Purkinje cell-specific DNA repair-deficient mouse model and a mouse model of spinocerebellar ataxia 1 revealed reduced transcription in Purkinje cells compared to controls. We combined EU labelling with immunohistology to correlate altered EU staining with pathological markers, such as genotoxic signalling factors. These data indicate that the EU-labelling method provided here can be used to identify changes in transcription in vivo in nervous system disease models.


1994 ◽  
Vol 71 (1) ◽  
pp. 401-419 ◽  
Author(s):  
E. De Schutter ◽  
J. M. Bower

1. Both excitatory and inhibitory postsynaptic channels were added to a previously described complex compartmental model of a cerebellar Purkinje cell to examine model responses to synaptic inputs. All model parameters remained as described previously, leaving maximum synaptic conductance as the only parameter that was tuned in the studies described in this paper. Under these conditions the model was capable of reproducing physiological recorded responses to each of the major types of synaptic input. 2. When excitatory synapses were activated on the smooth dendrites of the model, the model generated a complex dendritic Ca2+ spike similar to that generated by climbing fiber inputs. Examination of the model showed that activation of P-type Ca2+ channels in both the smooth and spiny dendrites augmented the depolarization during the complex spike and that Ca(2+)-activated K+ channels in the same dendritic regions determined the duration of the spike. When these synapses were activated under simulated current-clamp conditions the model also generated the characteristic dual reversal potential of the complex spike. The shape of the dendritic complex spike could be altered by changing the maximum conductance of the climbing fiber synapse and thus the amount of Ca2+ entering the cell. 3. To explore the background simple spike firing properties of Purkinje cells in vivo we added excitatory “parallel fiber” synapses to the spiny dendritic branches of the model. Continuous asynchronous activation of these granule cell synapses resulted in the generation of spontaneous sodium spikes. However, very low asynchronous input frequencies produced a highly regular, very fast rhythm (80–120 Hz), whereas slightly higher input frequencies resulted in Purkinje cell bursting. Both types of activity are uncharacteristic of in vivo Purkinje cell recordings. 4. Inhibitory synapses of the sort presumably generated by stellate cells were also added to the dendritic tree. When asynchronous activation of these inhibitory synapses was combined with continuous asynchronous excitatory input the model generated somatic action potentials in a much more stochastic pattern typical of real Purkinje cells. Under these conditions simulated inter-spike interval distributions resembled those found in experimental recordings. Also, as with in vivo recordings, the model did not generate dendritic bursts. This was mainly due to inhibition that suppressed the generation of dendritic Ca2+ spikes. 5. In the presence of asynchronous inhibition, changes in the average frequency of excitatory inputs modulated background simple spike firing frequencies in the natural range of Purkinje cell firing frequencies (30–100 Hz). This modulation was very sensitive to small changes in the average frequency of excitatory inputs.(ABSTRACT TRUNCATED AT 400 WORDS)


2013 ◽  
Vol 109 (5) ◽  
pp. 1333-1342 ◽  
Author(s):  
Qionger He ◽  
Heather Titley ◽  
Giorgio Grasselli ◽  
Claire Piochon ◽  
Christian Hansel

Ethanol profoundly influences cerebellar circuit function and motor control. It has recently been demonstrated that functional N-methyl-d-aspartate (NMDA) receptors are postsynaptically expressed at climbing fiber (CF) to Purkinje cell synapses in the adult cerebellum. Using whole cell patch-clamp recordings from mouse cerebellar slices, we examined whether ethanol can affect NMDA receptor signaling in mature Purkinje cells. NMDA receptor-mediated currents were isolated by bath application of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor antagonist 2,3-dihydroxy-6-nitro-7-sulfamoylbenzol[f]quinoxaline (NBQX). The remaining d-2-amino-5-phosphonovaleric acid (d-APV)-sensitive current was reduced by ethanol at concentrations as low as 10 mM. At a concentration of 50 mM ethanol, the blockade of d-APV-sensitive CF-excitatory postsynaptic currents was significantly stronger. Ethanol also altered the waveform of CF-evoked complex spikes by reducing the afterdepolarization. This effect was not seen when NMDA receptors were blocked by d-APV before ethanol wash-in. In contrast to CF synaptic transmission, parallel fiber (PF) synaptic inputs were not affected by ethanol. Finally, ethanol (10 mM) impaired long-term depression (LTD) at PF to Purkinje cell synapses as induced under control conditions by paired PF and CF activity. However, LTD induced by pairing PF stimulation with depolarizing voltage steps (substituting for CF activation) was not blocked by ethanol. These observations suggest that the sensitivity of cerebellar circuit function and plasticity to low concentrations of ethanol may be caused by an ethanol-mediated impairment of NMDA receptor signaling at CF synapses onto cerebellar Purkinje cells.


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