Calcium sensor regulation of the CaV2.1 Ca2+ channel contributes to short-term synaptic plasticity in hippocampal neurons

Short-term synaptic plasticity is induced by calcium (Ca2+) accumulating in presynaptic nerve terminals during repetitive action potentials. Regulation of voltage-gated CaV2.1 Ca2+ channels by Ca2+ sensor proteins induces facilitation of Ca2+ currents and synaptic facilitation in cultured neurons expressing exogenous CaV2.1 channels. However, it is unknown whether this mechanism contributes to facilitation in native synapses. We introduced the IM-AA mutation into the IQ-like motif (IM) of the Ca2+ sensor binding site. This mutation does not alter voltage dependence or kinetics of CaV2.1 currents, or frequency or amplitude of spontaneous miniature excitatory postsynaptic currents (mEPSCs); however, synaptic facilitation is completely blocked in excitatory glutamatergic synapses in hippocampal autaptic cultures. In acutely prepared hippocampal slices, frequency and amplitude of mEPSCs and amplitudes of evoked EPSCs are unaltered. In contrast, short-term synaptic facilitation in response to paired stimuli is reduced by ∼50%. In the presence of EGTA-AM to prevent global increases in free Ca2+, the IM-AA mutation completely blocks short-term synaptic facilitation, indicating that synaptic facilitation by brief, local increases in Ca2+ is dependent upon regulation of CaV2.1 channels by Ca2+ sensor proteins. In response to trains of action potentials, synaptic facilitation is reduced in IM-AA synapses in initial stimuli, consistent with results of paired-pulse experiments; however, synaptic depression is also delayed, resulting in sustained increases in amplitudes of later EPSCs during trains of 10 stimuli at 10–20 Hz. Evidently, regulation of CaV2.1 channels by CaS proteins is required for normal short-term plasticity and normal encoding of information in native hippocampal synapses.

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Parallel processing of quickly and slowly mobilized reserve vesicles in hippocampal synapses

10.1101/2020.08.14.251975 ◽

2020 ◽

Author(s):

Kashif Mahfooz ◽

Mathan K. Raja ◽

John F. Wesseling

Keyword(s):

Synaptic Plasticity ◽

Action Potentials ◽

High Probability ◽

Individual Action ◽

Short Term ◽

Reserve Pool ◽

Hippocampal Synapses ◽

In Series ◽

Fm Dyes ◽

Active Zones

AbstractQuickly and slowly mobilized reserve vesicles within presynaptic terminals are thought to be contained within separate pools that are connected in series. However, here we use FM-dyes to show that the two types are mobilized in parallel, without intermixing. The result supports a re-conceptualization of synaptic vesicle trafficking, proposed previously, where: (1) active zones contain multiple independent docking/release sites; (2) the release sites vary in probability of catalyzing exocytosis following individual action potentials; and (3), each docked vesicle is connected to a separate reserve. The re-conceptualization is then supported further by evidence that alterations in the timing of reserve pool depletion in synapsin knockouts are largest during lightest use even though alterations in short-term synaptic plasticity are largest during heavy use. The re-conceptualization implies that low release probability sites account for both reluctant readily releasable vesicles and slowly mobilized reserves. Extensive heterogeneity suggests that synapses have the capacity to store information by modulating the ratio of low to high probability release sites.

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Nonuniform Distribution and Contribution of P- and P/Q-Types Calcium Channels to Short-Term Inhibitory Synaptic Plasticity in Cultured Hippocampal Neurons

International Journal of Physiology and Pathophysiology ◽

10.1615/intjphyspathophys.v2.i3.60 ◽

2011 ◽

Vol 2 (3) ◽

pp. 259-268

Author(s):

Oksana P. Kolesnyk-Mizerna ◽

Svetlana A. Fedulova ◽

Nikolai S. Veselovsky

Keyword(s):

Synaptic Plasticity ◽

Calcium Channels ◽

Hippocampal Neurons ◽

Nonuniform Distribution ◽

Short Term ◽

Cultured Hippocampal Neurons

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Zinc Enhances the Inhibitory Effects of Strychnine-Sensitive Glycine Receptors in Mouse Hippocampal Neurons

Journal of Neurophysiology ◽

10.1152/jn.00500.2007 ◽

2007 ◽

Vol 98 (6) ◽

pp. 3666-3676 ◽

Cited By ~ 8

Author(s):

Hai Xia Zhang ◽

Liu Lin Thio

Keyword(s):

Action Potential ◽

Action Potentials ◽

Hippocampal Neurons ◽

Neuronal Excitability ◽

Hippocampal Slices ◽

Glycine Receptors ◽

Inhibitory Effects ◽

Action Potential Firing ◽

Embryonic Mouse ◽

Potential Firing

Although extracellular Zn2+ is an endogenous biphasic modulator of strychnine-sensitive glycine receptors (GlyRs), the physiological significance of this modulation remains poorly understood. Zn2+ modulation of GlyR may be especially important in the hippocampus where presynaptic Zn2+ is abundant. Using cultured embryonic mouse hippocampal neurons, we examined whether 1 μM Zn2+, a potentiating concentration, enhances the inhibitory effects of GlyRs activated by sustained glycine applications. Sustained 20 μM glycine (EC25) applications alone did not decrease the number of action potentials evoked by depolarizing steps, but they did in 1 μM Zn2+. At least part of this effect resulted from Zn2+ enhancing the GlyR-induced decrease in input resistance. Sustained 20 μM glycine applications alone did not alter neuronal bursting, a form of hyperexcitability induced by omitting extracellular Mg2+. However, sustained 20 μM glycine applications depressed neuronal bursting in 1 μM Zn2+. Zn2+ did not enhance the inhibitory effects of sustained 60 μM glycine (EC70) applications in these paradigms. These results suggest that tonic GlyR activation could decrease neuronal excitability. To test this possibility, we examined the effect of the GlyR antagonist strychnine and the Zn2+ chelator tricine on action potential firing by CA1 pyramidal neurons in mouse hippocampal slices. Co-applying strychnine and tricine slightly but significantly increased the number of action potentials fired during a depolarizing current step and decreased the rheobase for action potential firing. Thus Zn2+ may modulate neuronal excitability normally and in pathological conditions such as seizures by potentiating GlyRs tonically activated by low agonist concentrations.

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MicroRNA132 Modulates Short-Term Synaptic Plasticity but Not Basal Release Probability in Hippocampal Neurons

PLoS ONE ◽

10.1371/journal.pone.0015182 ◽

2010 ◽

Vol 5 (12) ◽

pp. e15182 ◽

Cited By ~ 45

Author(s):

Talley J. Lambert ◽

Daniel R. Storm ◽

Jane M. Sullivan

Keyword(s):

Synaptic Plasticity ◽

Hippocampal Neurons ◽

Short Term ◽

Release Probability ◽

Basal Release

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Pharmacological and kinetic characterization of two functional classes of serotonergic modulation in Aplysia sensory neurons

Journal of Neurophysiology ◽

10.1152/jn.1996.75.2.855 ◽

1996 ◽

Vol 75 (2) ◽

pp. 855-866 ◽

Cited By ~ 12

Author(s):

L. L. Stark ◽

A. R. Mercer ◽

N. J. Emptage ◽

T. J. Carew

Keyword(s):

Synaptic Transmission ◽

Sensory Neurons ◽

Time Course ◽

Behavioral Sensitization ◽

Input Resistance ◽

Short Term ◽

Synaptic Facilitation ◽

Functional Classes ◽

Kinetics Of ◽

Serotonergic Modulation

1. Modulation of mechanoafferent sensory neurons (SNs) by the neutrotransmitter serotonin (5HT) plays a significant role in behavioral sensitization of several withdrawal reflexes in Aplysia. The modulatory effects of 5HT on these SNs include increased excitability, increased input resistance, action potential broadening, and increased synaptic transmission. Based on a previously described dissociation of some of these modulatory effects, revealed with the 5HT-receptor antagonist, cyproheptadine, we investigated whether a similar dissociation could be found by systematically varying the concentration of the endogenous agonist, 5HT. 2. We first applied a range of 5HT concentrations to isolated pleural/pedal ganglia (containing tail SNs and tail motor neurons, respectively), and measured the magnitude of 5HT-induced modulation of spike broadening and increased excitability. The resulting dose-response curve showed that both forms of modulation increase monotonically as a function of 5HT concentration, but that excitability has a lower threshold for modulation by 5HT than does spike duration. 3. We further characterized the modulatory effects of 5HT on Aplysia SNs by comparing the time course of onset of modulation by 5HT and the time course of recovery after washout. Independent of 5HT concentration, modulation of excitability increases rapidly in the presence of 5HT and recovers rapidly (< 3 min) after washout. Similarly, input resistance increases and recovers rapidly, mirroring the profile of increased excitability. However, modulation of spike duration exhibits two profiles, dependent on 5HT concentration. Low concentrations of 5HT (0.5 and 1 microM) induce a rapid-onset and transient-recovery form of spike broadening, which resembles the kinetics of increased excitability and increased input resistance. Higher concentrations of 5HT (2.5 and 5 microM) induce a more slowly developing and prolonged-recovery form of spike broadening (> 9 min). At these higher concentrations, the recovery profile for prolonged spike broadening is significantly different from those observed for both increased excitability and increased input resistance. 4. We next compared the relationship between spike broadening and short-term synaptic facilitation. We found that significant facilitation of synaptic transmission requires a high 5HT concentration, which is comparable with that required to induce prolonged spike broadening. Similarly, the recovery profiles for spike broadening and synaptic facilitation are strikingly similar, recovering in parallel. 5. Our experiments show that the modulatory effects of 5HT in the tail SNs can be dissociated both by their sensitivity to different concentrations of 5HT and by their kinetics of serotonergic modulation. Based on these results, together with extensive evidence from other laboratories, we propose that the short-term modulatory effects of 5HT fall into two distinct functional classes. The first class, which includes excitability, input resistance, and transient spike broadening, has a low threshold for 5HT modulation and recovers rapidly. The second class, which includes prolonged spike broadening and short-term synaptic facilitation, has a higher threshold for modulation and recovers more slowly. It now will be of interest to determine the functional contribution of each of these classes to different aspects of sensitization.

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Ca2+-Dependent, Stimulus-Specific Modulation of the Plasma Membrane Ca2+ Pump in Hippocampal Neurons

Journal of Neurophysiology ◽

10.1152/jn.90774.2008 ◽

2009 ◽

Vol 101 (5) ◽

pp. 2563-2571 ◽

Cited By ~ 7

Author(s):

Michael J. Ferragamo ◽

Jessica L. Reinardy ◽

Stanley A. Thayer

Keyword(s):

Plasma Membrane ◽

Neuronal Activity ◽

Action Potentials ◽

Hippocampal Neurons ◽

Cyclopiazonic Acid ◽

Synaptic Activity ◽

Voltage Gated ◽

Clearance Kinetics ◽

Transient Elevation ◽

Kinetics Of

The plasma membrane Ca2+ ATPase (PMCA) plays a major role in restoring Ca2+ to basal levels following transient elevation by neuronal activity. Here we examined the effects of various stimuli that increase [Ca2+]i on PMCA-mediated Ca2+ clearance from hippocampal neurons. We used indo-1-based microfluorimetry in the presence of cyclopiazonic acid to study the rate of PMCA-mediated recovery of Ca2+ elevated by a brief train of action potentials. [Ca2+]i recovery was described by an exponential decay and the time constant provided an index of PMCA-mediated Ca2+ clearance. PMCA function was assessed before and for ≥60 min following a 10-min priming stimulus of either 100 μM N-methyl-d-aspartate (NMDA), 0.1 mM Mg2+ (reduced extracellular Mg2+ induces intense excitatory synaptic activity), 30 mM K+, or control buffer. Recovery kinetics slowed progressively following priming with NMDA or 0.1 mM Mg2+; in contrast, Ca2+ clearance initially accelerated and then slowly returned to initial rates following priming with 30 mM K+-induced depolarization. Treatment with 10 μM calpeptin, an inhibitor of the Ca2+ activated protease calpain, prevented the slowing of kinetics observed following treatment with NMDA but had no affect on the recovery kinetics of control cells. Calpeptin also blocked the rapid acceleration of Ca2+ clearance following depolarization. In calpeptin-treated cells, 0.1 mM Mg2+ induced a graded acceleration of Ca2+ clearance. Thus in spite of producing comparable increases in [Ca2+]i, activation of NMDA receptors, depolarization-induced activation of voltage-gated Ca2+ channels and excitatory synaptic activity each uniquely affected Ca2+ clearance kinetics mediated by the PMCA.

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New insights into short-term synaptic facilitation at the frog neuromuscular junction

Journal of Neurophysiology ◽

10.1152/jn.00198.2014 ◽

2015 ◽

Vol 113 (1) ◽

pp. 71-87 ◽

Cited By ~ 8

Author(s):

Jun Ma ◽

Lauren Kelly ◽

Justin Ingram ◽

Thomas J. Price ◽

Stephen D. Meriney ◽

...

Keyword(s):

Neuromuscular Junction ◽

Calcium Binding ◽

High Frequency Stimulation ◽

Frog Neuromuscular Junction ◽

Short Term ◽

Calcium Binding Site ◽

Synaptic Facilitation ◽

Site Model ◽

Computer Simulation Studies ◽

Sensor Proteins

Short-term synaptic facilitation occurs during high-frequency stimulation, is known to be dependent on presynaptic calcium ions, and persists for tens of milliseconds after a presynaptic action potential. We have used the frog neuromuscular junction as a model synapse for both experimental and computer simulation studies aimed at testing various mechanistic hypotheses proposed to underlie short-term synaptic facilitation. Building off our recently reported excess-calcium-binding-site model of synaptic vesicle release at the frog neuromuscular junction (Dittrich M, Pattillo JM, King JD, Cho S, Stiles JR, Meriney SD. Biophys J 104: 2751–2763, 2013), we have investigated several mechanisms of short-term facilitation at the frog neuromuscular junction. Our studies place constraints on previously proposed facilitation mechanisms and conclude that the presence of a second class of calcium sensor proteins distinct from synaptotagmin can explain known properties of facilitation observed at the frog neuromuscular junction. We were further able to identify a novel facilitation mechanism, which relied on the persistent binding of calcium-bound synaptotagmin molecules to lipids of the presynaptic membrane. In a real physiological context, both mechanisms identified in our study (and perhaps others) may act simultaneously to cause the experimentally observed facilitation. In summary, using a combination of computer simulations and physiological recordings, we have developed a stochastic computer model of synaptic transmission at the frog neuromuscular junction, which sheds light on the facilitation mechanisms in this model synapse.

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RIM-binding protein 2 regulates release probability by fine-tuning calcium channel localization at murine hippocampal synapses

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1605256113 ◽

2016 ◽

Vol 113 (41) ◽

pp. 11615-11620 ◽

Cited By ~ 45

Author(s):

M. Katharina Grauel ◽

Marta Maglione ◽

Suneel Reddy-Alla ◽

Claudia G. Willmes ◽

Marisa M. Brockmann ◽

...

Keyword(s):

Hippocampal Neurons ◽

Autism Spectrum ◽

Fine Tuning ◽

Model Systems ◽

Short Term ◽

Superresolution Microscopy ◽

Release Probability ◽

Spatial Coupling ◽

Hippocampal Synapses ◽

Initial Release

The tight spatial coupling of synaptic vesicles and voltage-gated Ca2+ channels (CaVs) ensures efficient action potential-triggered neurotransmitter release from presynaptic active zones (AZs). Rab-interacting molecule-binding proteins (RIM-BPs) interact with Ca2+ channels and via RIM with other components of the release machinery. Although human RIM-BPs have been implicated in autism spectrum disorders, little is known about the role of mammalian RIM-BPs in synaptic transmission. We investigated RIM-BP2–deficient murine hippocampal neurons in cultures and slices. Short-term facilitation is significantly enhanced in both model systems. Detailed analysis in culture revealed a reduction in initial release probability, which presumably underlies the increased short-term facilitation. Superresolution microscopy revealed an impairment in CaV2.1 clustering at AZs, which likely alters Ca2+ nanodomains at release sites and thereby affects release probability. Additional deletion of RIM-BP1 does not exacerbate the phenotype, indicating that RIM-BP2 is the dominating RIM-BP isoform at these synapses.

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Endocannabinoid- and mGluR5-Dependent Short-Term Synaptic Depression in an Isolated Neuron/Bouton Preparation From the Hippocampal CA1 Region

Journal of Neurophysiology ◽

10.1152/jn.90226.2008 ◽

2008 ◽

Vol 100 (2) ◽

pp. 1041-1052 ◽

Cited By ~ 21

Author(s):

Anton Sheinin ◽

Giuseppe Talani ◽

Margaret I. Davis ◽

David M. Lovinger

Keyword(s):

Hippocampal Neurons ◽

Basolateral Amygdala ◽

Pyramidal Neurons ◽

Metabotropic Glutamate Receptor ◽

Hippocampal Slices ◽

Neuronal Membrane ◽

Short Term ◽

Ca1 Region ◽

Hippocampal Ca1 Region ◽

Isolated Neuron

Endocannabinoids released from the postsynaptic neuronal membrane can activate presynaptic CB1 receptors and inhibit neurotransmitter release. In hippocampal slices, depolarization of the CA1 pyramidal neurons elicits an endocannabinoid-mediated inhibition of γ-aminobutyric acid release known as depolarization-induced suppression of inhibition (DSI). Using the highly reduced neuron/synaptic bouton preparation from the CA1 region of hippocampus, we have begun to examine endocannabinoid-dependent short-term depression (STD) of inhibitory synaptic transmission under well-controlled physiological and pharmacological conditions in an environment free of other cells. Application of the CB1 synthetic agonist WIN55212 -2 and endogenous cannabinoids 2-AG and anandamide produced a decrease in spontaneous inhibitory postsynaptic current (sIPSC) frequency and amplitude, indicating the presence of CB1 receptors at synapses in this preparation. Endocannabinoid-dependent STD is different from DSI found in hippocampal slices and the neuron/bouton preparation from basolateral amygdala (BLA) since depolarization alone was not sufficient to induce suppression of sIPSCs. However, concurrent application of the metabotropic glutamate receptor (mGluR) agonist ( RS)-3,5-dihydroxyphenylglycine (DHPG) and postsynaptic depolarization resulted in a transient (30–50 s) decrease in sIPSC frequency and amplitude. Application of DHPG alone had no effect on sIPSCs. The depolarization/DHPG-induced STD was blocked by the CB1 antagonist SR141716A and the mGluR5 antagonist MPEP and was sensitive to intracellular calcium concentration. Comparing the present findings with earlier work in hippocampal slices and BLA, it appears that endocannabinoid release is less robust in isolated hippocampal neurons.

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