Loss of Doc2b does not influence transmission at Purkinje cell to deep nuclei synapses under physiological conditions

Time Course ◽

Cultured Cells ◽

Cerebellar Nuclei ◽

Physiological Conditions ◽

Sustained Activity ◽

Doc2a and Doc2b are high-affinity calcium-binding proteins that interact with SNARE proteins and phospholipids. Experiments performed on cultured cells indicated that Doc2 proteins promote spontaneous vesicle fusion and asynchronous neurotransmitter release, regulate vesicle priming, mediate augmentation, and regulate transmission during sustained activity. Here, we assess the role of Doc2 proteins in synaptic transmission under physiological conditions at mature synapses made by Purkinje cells onto neurons in the deep cerebellar nuclei (PC to DCN synapses). PCs express Doc2b but not Doc2a. Surprisingly, spontaneous neurotransmitter release, synaptic strength, the time course of evoked release, responses evoked by sustained high-frequency stimulation, and short-term plasticity were normal in Doc2b KO mice. Thus, in stark contrast to numerous functions previously proposed for Doc2, here we find that Doc2b removal does not influence transmission at PC-to-DCN synapses, indicating that conclusions based on studies of Doc2b in cultured cells do not necessarily generalize to mature synapses under physiological conditions.

Signalling by CGRP and Adrenomedullin in the Cerebellum and Other Systems

The Scientific World JOURNAL ◽

10.1100/tsw.2001.434 ◽

2001 ◽

Vol 1 ◽

pp. 11-11

Author(s):

David Poyner ◽

Heather Cater ◽

Nick Hartell ◽

Alex Conner ◽

Debbie Hay ◽

...

Keyword(s):

Tyrosine Kinases ◽

Transmitter Release ◽

Cultured Cells ◽

Signalling Pathways ◽

Nerve Terminals ◽

Parallel Fibre ◽

Isolated Tissues ◽

Stimulation Of

The best characterised signalling pathway activated by both CGRP and adrenomedullin is stimulation of adenylate cyclase via Gs. However, it is clear that in some circumstances the peptides can activate other signal transduction pathways, e.g., increases in intracellular calcium. Many of these signalling pathways can be observed in cultured cells but it is important also to examine isolated tissues to discover the full repertoire of transduction events. In the rat cerebellum there are receptors that respond to both CGRP and adrenomedullin. These seem to be located postsynaptically on Parallel Fibre nerve terminals and modulate transmission to Purkinje cells. Adrenomedullin acts via cAMP, apparently to augment neurotransmitter release. By contrast, CGRP decreases transmitter release, via a non-cAMP mediated pathway. We are currently examining the role of NO and tyrosine kinases in the responses to these peptides.

Role of fascia in maintenance of muscle tension and pressure

Journal of Applied Physiology ◽

10.1152/jappl.1981.51.2.317 ◽

1981 ◽

Vol 51 (2) ◽

pp. 317-320 ◽

Cited By ~ 66

Author(s):

S. R. Garfin ◽

C. M. Tipton ◽

S. J. Mubarak ◽

S. L. Woo ◽

A. R. Hargens ◽

...

Keyword(s):

High Frequency ◽

Muscle Tension ◽

Fluid Pressure ◽

Low Frequency ◽

Testing Procedure ◽

Force Transducer ◽

Low Frequency Stimulation ◽

The effect of fasciotomy on muscle tension (measured by a force transducer attached to the tendon) and interstitial fluid pressure (measured by Wick catheters in the muscle belly) was studied in the anterolateral compartments of 13 dog hindlimbs. Muscle tension and pressure were monitored in the tibialis cranialis muscle after low- and high-frequency stimulation of the peroneal nerve to produce twitch- and tetanic-type contractions. Fasciotomy decreased muscle force during the low-frequency stimulation by 16% (35.3 +/- 4.9 to 28.4 +/- 3.9 N) and during the high-frequency stimulation by 10% (60.8 %/- 4.9 to 54.8 +/- 3.9 N). Muscle pressure decreased 50% after fasciotomy under both conditions, 15 +/- 2 to 6 +/- 1 mmHg and 84 +/- 17 to 41 +/- 8 mmHg), respectively. Repeated functional evaluations during the testing procedure indicated that muscle fatigue was not a major factor in these results. It was concluded that fascia is important in the development of muscle tension and changes in interstitial pressure. Furthermore, the results raised questions concerning the merits of performing a fasciotomy for athletes with a compartment syndrome.

Rescue of motoneuron and muscle afferent function in cats by regeneration into skin. II. Ia-motoneuron synapse

10.1152/jn.1995.73.2.662 ◽

1995 ◽

Vol 73 (2) ◽

pp. 662-673 ◽

Cited By ~ 29

Author(s):

L. M. Mendell ◽

J. S. Taylor ◽

R. D. Johnson ◽

J. B. Munson

Keyword(s):

High Frequency ◽

Muscle Afferents ◽

Medial Gastrocnemius ◽

Lateral Gastrocnemius ◽

Essentially Normal ◽

Muscle Afferent ◽

Muscle Nerve ◽

1. In this study we describe application of high-frequency stimulation to the group Ia afferent-to-motoneuron synapse of cats to determine the extent to which regeneration of axotomized muscle afferents and motoneurons into skin or into muscle rescues their ability to generate excitatory postsynaptic potentials (EPSPs). 2. The medial gastrocnemius (MG) muscle nerve was transected and 1) left chronically axotomized, 2) cross-united to the caudal cutaneous sural (CCS) nerve, or 3) self-united. The ability of the operated MG muscle afferents to generate EPSPs in normal lateral gastrocnemius-soleus (LGS) motoneurons and of normal LGS muscle afferents to generate EPSPs in the operated MG motoneurons was tested 5 wk-30 mo later. 3. EPSPs were generated by bursts of 32 shocks at 167 Hz and averaged in register. In normal cats, EPSP amplitude decreased (negative modulation) during these bursts in type S motoneurons and could increase or decrease in type F motoneurons (positive or negative modulation). 4. After axotomy, EPSPs generated both in axotomized motoneurons and by axotomized afferents showed only negative modulation during the burst, and the negative modulation was much greater than in normal animals. Regeneration of the muscle nerve into skin significantly decreased the negative modulation relative to axotomy. Regeneration of the muscle nerve into muscle restored the EPSP modulation behaviors even more, to essentially normal values. 5. We conclude that the ability of muscle afferents to generate EPSPs in motoneurons in response to high-frequency stimulation, and the ability of motoneurons to express those EPSPs, are both influenced by the target innervated by those neurons. Synaptic efficacy is severely reduced by target deprivation (axotomy), partially rescued by cross-regeneration into skin, and rescued virtually completely by regeneration into the native muscle. We speculate on the role of target-derived neurotrophins in these effects.

Neurotransmitter release from high-frequency stimulation of the subthalamic nucleus

Journal of Neurosurgery ◽

10.3171/jns.2004.101.3.0511 ◽

2004 ◽

Vol 101 (3) ◽

pp. 511-517 ◽

Cited By ~ 113

Author(s):

Kendall H. Lee ◽

Su-Youne Chang ◽

David W. Roberts ◽

Uhnoh Kim

Keyword(s):

Action Potential ◽

High Frequency ◽

Content Type ◽

Action Potential Frequency ◽

Frequency Stimulation ◽

Potential Frequency ◽

Fine Print ◽

Stimulation Of

Object. High-frequency stimulation (HFS) delivered through implanted electrodes in the subthalamic nucleus (STN) has become an established treatment for Parkinson disease (PD). The precise mechanism of action of deep brain stimulation (DBS) in the STN is unknown, however. In the present study, the authors tested the hypothesis that HFS within the STN changes neuronal action potential firing rates during the stimulation period by modifying neurotransmitter release. Methods. Intracellular electrophysiological recordings were obtained using sharp electrodes in rat STN neurons in an in vitro slice preparation. A concentric bipolar stimulating electrode was placed in the STN slice, and electrical stimulation (pulse width 50–100 µsec, duration 100–2000 µsec, amplitude 10–500 µA, and frequency 10–200 Hz) was delivered while simultaneously obtaining intracellular recordings from an STN neuron. High-frequency stimulation of the STN either generated excitatory postsynaptic potentials (EPSPs) and increased the action potential frequency or it generated inhibitory postsynaptic potentials and decreased the action potential frequency of neurons within the STN. These effects were blocked after antagonists to glutamate and γ-aminobutyric acid were applied to the tissue slice, indicating that HFS resulted in the release of neurotransmitters. Intracellular recordings from substantia nigra pars compacta (SNc) dopaminergic neurons during HFS of the STN revealed increased generation of EPSPs and increased frequency of action potentials in SNc neurons. Conclusions. During HFS of STN neurons the mechanism of DBS may involve the release of neurotransmitters rather than the primary electrogenic inhibition of neurons.

Differential Effects of SNAP-25 Deletion on Ca2+-Dependent and Ca2+-Independent Neurotransmission

10.1152/jn.00226.2007 ◽

2007 ◽

Vol 98 (2) ◽

pp. 794-806 ◽

Cited By ~ 79

Author(s):

Peter Bronk ◽

Ferenc Deák ◽

Michael C. Wilson ◽

Xinran Liu ◽

Thomas C. Südhof ◽

...

Keyword(s):

Neuronal Cultures ◽

Inhibitory Neurotransmitter ◽

Calcium Dependent ◽

Receptor Complexes ◽

Readily Releasable Pool ◽

Protein Receptor ◽

Frequency Stimulation ◽

Hypertonic Stimulation

At the synapse, SNAP-25, along with syntaxin/HPC-1 and synaptobrevin/VAMP, forms SNARE N-ethylmaleimide-sensitive factor [soluble (NSF) attachment protein receptor] complexes that are thought to catalyze membrane fusion. Results from neuronal cultures of synaptobrevin-2 knockout (KO) mice showed that loss of synaptobrevin has a more severe effect on calcium-evoked release than on spontaneous release or on release evoked by hypertonicity. In this study, we recorded neurotransmitter release from neuronal cultures of SNAP-25 KO mice to determine whether they share this property. In neurons lacking SNAP-25, as those deficient in synaptobrevin-2, we found that ∼10–12% of calcium-independent excitatory and inhibitory neurotransmitter release persisted. However, in contrast to synaptobrevin-2 knockouts, this remaining readily releasable pool in SNAP-25-deficient synapses was virtually insensitive to calcium-dependent–evoked stimulation. Although field stimulation reliably evoked neurotransmitter release in synaptobrevin-2 KO neurons, responses were rare in neurons lacking SNAP-25, and unlike synaptobrevin-2–deficient synapses, SNAP-25–deficient synapses did not exhibit facilitation of release during high-frequency stimulation. This severe loss of evoked exocytosis was matched by a reduction, but not a complete loss, of endocytosis during evoked stimulation. Moreover, synaptic vesicle turnover probed by FM-dye uptake and release during hypertonic stimulation was relatively unaffected by the absence of SNAP-25. This last difference indicates that in contrast to synaptobrevin, SNAP-25 does not directly function in endocytosis. Together, these results suggest that SNAP-25 has a more significant role in calcium-secretion coupling than synaptobrevin-2.

Modulation of synaptic transmission at Ia-afferent fiber connections on motoneurons during high-frequency stimulation: role of postsynaptic target

10.1152/jn.1991.65.3.590 ◽

1991 ◽

Vol 65 (3) ◽

pp. 590-597 ◽

Cited By ~ 38

Author(s):

H. R. Koerber ◽

L. M. Mendell

Keyword(s):

High Frequency ◽

Afferent Fiber ◽

Excitatory Postsynaptic Potential ◽

Epsp Amplitude ◽

Marked Variability ◽

Frequency Stimulation ◽

Frequency Burst ◽

Stimulation Of

1. High-frequency stimulation of single group Ia-fibers results in modulation of excitatory postsynaptic potential (EPSP) amplitude recorded in target motoneurons. This can be either positive (EPSP amplitude increases in response to successive stimuli in the high-frequency burst) or negative (decrease in EPSP amplitude). We have investigated whether the magnitude of modulation is associated with the stimulated afferent, the responding motoneuron, or the amplitude of the EPSP. 2. In agreement with previous findings, we found that positive modulation tends to occur at connections generating small EPSPs and negative modulation, at those producing large EPSPs. Because large EPSPs generally are evoked in motoneurons with low values of rheobase, we found, as anticipated, that connections on low rheobase motoneurons are prone to negative modulation during high-frequency stimulation, whereas those on high rheobase motoneurons (which tend to generate small EPSPs) are prone to positive modulation. 3. In experiments where the projection of multiple afferents to a single motoneuron was studied, we found that amplitude modulation was similar despite differences in EPSP amplitude. Thus in a given motoneuron there is no relationship between modulation and amplitude, in contrast to the existence of such a relationship in the population of connections as a whole. 4. In the converse experiments where the projection of single afferents to multiple motoneurons was studied, we found marked variability in the modulation patterns with clear indications that amplitude and modulation are correlated as in the entire population of Ia/motoneuron connections. 5. We tested the constancy of modulation patterns evoked in a given motoneuron by comparing the modulation patterns evoked in motoneurons by single fibers, and by stimulation of the heteronymous nerve.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrochemical characterization of high frequency stimulation electrodes: role of electrode material and stimulation parameters on electrode polarization

Journal of Neural Engineering ◽

10.1088/1741-2552/aa9f31 ◽

2018 ◽

Vol 15 (3) ◽

pp. 036023 ◽

Cited By ~ 4

Author(s):

Atefeh Ghazavi ◽

Stuart F Cogan

Keyword(s):

Electrode Material ◽

High Frequency ◽

Electrochemical Characterization ◽

Electrode Polarization ◽

Stimulation Parameters ◽

Transverse tubule remodeling enhances Orai1-dependent Ca2+ entry in skeletal muscle

eLife ◽

10.7554/elife.47576 ◽

2019 ◽

Vol 8 ◽

Cited By ~ 6

Author(s):

Antonio Michelucci ◽

Simona Boncompagni ◽

Laura Pietrangelo ◽

Maricela García-Castañeda ◽

Takahiro Takano ◽

...

Keyword(s):

Skeletal Muscle ◽

Time Course ◽

Acute Exercise ◽

Muscle Force ◽

Contractile Function ◽

Force Production ◽

Frequency Stimulation ◽

Muscle Force Production ◽

Muscle Contractile

Exercise promotes the formation of intracellular junctions in skeletal muscle between stacks of sarcoplasmic reticulum (SR) cisternae and extensions of transverse-tubules (TT) that increase co-localization of proteins required for store-operated Ca2+ entry (SOCE). Here, we report that SOCE, peak Ca2+ transient amplitude and muscle force production during repetitive stimulation are increased after exercise in parallel with the time course of TT association with SR-stacks. Unexpectedly, exercise also activated constitutive Ca2+ entry coincident with a modest decrease in total releasable Ca2+ store content. Importantly, this decrease in releasable Ca2+ store content observed after exercise was reversed by repetitive high-frequency stimulation, consistent with enhanced SOCE. The functional benefits of exercise on SOCE, constitutive Ca2+ entry and muscle force production were lost in mice with muscle-specific loss of Orai1 function. These results indicate that TT association with SR-stacks enhances Orai1-dependent SOCE to optimize Ca2+ dynamics and muscle contractile function during acute exercise.

ALG-2 interacting protein-X (Alix) is required for activity-dependent bulk endocytosis at brain synapses

10.1101/2020.07.20.211854 ◽

2020 ◽

Author(s):

Marine H. Laporte ◽

Kwang Il Chi ◽

Marta Rolland ◽

Laura C. Caudal ◽

José Martinez-Hernandez ◽

...

Keyword(s):

Calcium Binding ◽

Epileptiform Activity ◽

Adaptor Protein ◽

Contralateral Side ◽

Interacting Protein ◽

Protein X ◽

Frequency Stimulation ◽

Chemical Synapses ◽

Activity Dependent

AbstractIn chemical synapses undergoing high frequency stimulation, vesicle components can be retrieved from the plasma membrane via a clathrin-independent process called activity dependent bulk endocytosis (ADBE). Alix (ALG-2 interacting protein X)/ PDCD6IP) is an adaptor protein binding to ESCRT and endophilin-A proteins and thereby driving deformation and fission of endosomal and cell surface membranes. In fibroblasts, Alix is required for clathrin-independent endocytosis. Here, using electron microscopy, we show that synapses from mice lacking Alix have subtle defects in presynaptic compartments, translating into flawed synaptic plasticity. Using cultured neurons, we demonstrate that Alix is required for ADBE. We further demonstrate that in order to perform ADBE, Alix must be recruited to synapses by the calcium-binding protein ALG-2 and interact with endophilin-A. Finally, we show that mutant mice lacking Alix in the forebrain undergo less seizures during kainate-induced status epilepticus. Furthermore, propagation of the epileptiform activity to the contralateral side of kainate injection is reduced. These results thus highlight Alix ko mice as an invaluable model to study the exact role of ADBE at synapses undergoing physiological or pathological stimulations.

Patterned Activity in Stratum Lacunosum Moleculare Inhibits CA1 Pyramidal Neuron Firing

10.1152/jn.1999.82.6.3213 ◽

1999 ◽

Vol 82 (6) ◽

pp. 3213-3222 ◽

Cited By ~ 46

Author(s):

Hannah Dvorak-Carbone ◽

Erin M. Schuman

Keyword(s):

Time Course ◽

Pyramidal Cells ◽

Stratum Radiatum ◽

Dependent Manner ◽

Ca1 Pyramidal Cells ◽

Frequency Stimulation ◽

Primary Output ◽

Ca1 Pyramidal Neuron ◽

Stratum Lacunosum Moleculare

CA1 pyramidal cells are the primary output neurons of the hippocampus, carrying information about the result of hippocampal network processing to the subiculum and entorhinal cortex (EC) and thence out to the rest of the brain. The primary excitatory drive to the CA1 pyramidal cells comes via the Schaffer collateral (SC) projection from area CA3. There is also a direct projection from EC to stratum lacunosum-moleculare (SLM) of CA1, an input well positioned to modulate information flow through the hippocampus. High-frequency stimulation in SLM evokes an inhibition sufficiently strong to prevent CA1 pyramidal cells from spiking in response to SC input, a phenomenon we refer to as spike-blocking. We characterized the spike-blocking efficacy of burst stimulation (10 stimuli at 100 Hz) in SLM and found that it is greatest at ∼300–600 ms after the burst, consistent with the time course of the slow GABABsignaling pathway. Spike-blocking efficacy increases in potency with the number of SLM stimuli in a burst, but also decreases with repeated presentations of SLM bursts. Spike-blocking was eliminated in the presence of GABABantagonists. We have identified a candidate population of interneurons in SLM and distal stratum radiatum (SR) that may mediate this spike-blocking effect. We conclude that the output of CA1 pyramidal cells, and hence the hippocampus, is modulated in an input pattern-dependent manner by activation of the direct pathway from EC.