scholarly journals Plasticity manifolds: Conjunctive changes in multiple ion channels mediate activity-dependent plasticity in hippocampal granule cells

2019 ◽  
Author(s):  
Poonam Mishra ◽  
Rishikesh Narayanan
Keyword(s):  
Granule Cells ◽  
Calcium Influx ◽  
Burst Firing ◽  
Action Potential Firing ◽  
Whole Cell Patch Clamp ◽  
Potential Firing ◽  
Intrinsic Plasticity ◽  
The Impact ◽  
Activity Dependent ◽  
Theta Burst

AbstractThe dentate gyrus (DG) was the first brain region to provide insights about synaptic and intrinsic plasticity. However, the assessment of intrinsic plasticity in DG has been surprisingly limited. We employed whole-cell patch-clamp recordings to explore the impact of behaviorally relevant theta-modulated burst firing, in the absence of synaptic stimulation, on intrinsic properties of rat DG granule cells. We found that theta burst firing induced a significant reduction in sub-threshold excitability and temporal summation, accompanied by an unexpectedly contrasting enhancement of action potential firing rate. We show that conjunctive changes in HCN, inward-rectifier potassium and persistent sodium channels mediated this form of plasticity, which was dependent on calcium influx through L-type calcium channels and inositol trisphosphate receptors. Our results unveil the expression of conjunctive plasticity in multiple channels, responding to the same activity pattern, establishing a plasticity manifold that could concomitantly mediate encoding and homeostasis in DG engram cells.

BICUCULLINE/BACLOFEN-INSENSITIVE GABA RESPONSE IN CRUSTACEAN NEURONES IN CULTURE

1994 ◽  
Vol 191 (1) ◽  
pp. 167-193
Author(s):  
C Jackel ◽  
W Krenz ◽  
F Nagy
Keyword(s):  
Reversal Potential ◽  
Membrane Conductance ◽  
Gamma Aminobutyric Acid ◽  
Action Potential Firing ◽  
Patch Clamp Technique ◽  
Conformationally Restricted ◽  
Whole Cell Patch Clamp ◽  
Gabac Receptor ◽  
Potential Firing ◽  
Sr 95531

Neurones were dissociated from thoracic ganglia of embryonic and adult lobsters and kept in primary culture. When gamma-aminobutyric acid (GABA) was applied by pressure ejection, depolarizing or hyperpolarizing responses were produced, depending on the membrane potential. They were accompanied by an increase in membrane conductance. When they were present, action potential firing was inhibited. The pharmacological profile and ionic mechanism of GABA-evoked current were investigated under voltage-clamp with the whole-cell patch-clamp technique. The reversal potential of GABA-evoked current depended on the intracellular and extracellular Cl- concentration but not on extracellular Na+ and K+. Blockade of Ca2+ channels by Mn2+ was also without effect. The GABA-evoked current was mimicked by application of the GABAA agonists muscimol and isoguvacine with an order of potency muscimol>GABA>isoguvacine. cis-4-aminocrotonic acid (CACA), a folded and conformationally restricted GABA analogue, supposed to be diagnostic for the vertebrate GABAC receptor, also induced a bicuculline-resistant chloride current, although with a potency about 10 times lower than that of GABA. The GABA-evoked current was largely blocked by picrotoxin, but was insensitive to the GABAA antagonists bicuculline, bicuculline methiodide and SR 95531 at concentrations of up to 100 µmol l-1. Diazepam and phenobarbital did not exert modulatory effects. The GABAB antagonist phaclophen did not affect the GABA-induced current, while the GABAB agonists baclophen and 3-aminopropylphosphonic acid (3-APA) never evoked any response. Our results suggest that lobster thoracic neurones in culture express a chloride-conducting GABA-receptor channel which conforms to neither the GABAA nor the GABAB types of vertebrates but shows a pharmacology close to that of the novel GABAC receptor described in the vertebrate retina.

scholarly journals Silent synapses generate sparse and orthogonal action potential firing in adult-born hippocampal granule cells

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Liyi Li ◽  
Sébastien Sultan ◽  
Stefanie Heigele ◽  
Charlotte Schmidt-Salzmann ◽  
Nicolas Toni ◽  
...  
Keyword(s):  
Ampa Receptors ◽  
Developmental Stages ◽  
Granule Cells ◽  
Action Potential Firing ◽  
Adult Mice ◽  
Silent Synapses ◽  
Afferent Fibers ◽  
Potential Firing ◽  
Sparse Connectivity ◽  
Early Developmental

In adult neurogenesis young neurons connect to the existing network via formation of thousands of new synapses. At early developmental stages, glutamatergic synapses are sparse, immature and functionally 'silent', expressing mainly NMDA receptors. Here we show in 2- to 3-week-old young neurons of adult mice, that brief-burst activity in glutamatergic fibers is sufficient to induce postsynaptic AP firing in the absence of AMPA receptors. The enhanced excitability of the young neurons lead to efficient temporal summation of small NMDA currents, dynamic unblocking of silent synapses and NMDA-receptor-dependent AP firing. Therefore, early synaptic inputs are powerfully converted into reliable spiking output. Furthermore, due to high synaptic gain, small dendritic trees and sparse connectivity, neighboring young neurons are activated by different distinct subsets of afferent fibers with minimal overlap. Taken together, synaptic recruitment of young neurons generates sparse and orthogonal AP firing, which may support sparse coding during hippocampal information processing.

scholarly journals Activity-Dependent Gene Expression in Neurons

2020 ◽  
pp. 107385842094351
Author(s):  
Philip R. Lee ◽  
R. Douglas Fields
Keyword(s):  
Gene Expression ◽  
Intracellular Signaling ◽  
Action Potential Firing ◽  
Expression Of Genes ◽  
Neuronal Gene ◽  
Potential Firing ◽  
Processing Information ◽  
Subcellular Compartmentation ◽  
Temporal Firing ◽  
Activity Dependent

The function of the nervous system in conveying and processing information necessary to interact with the environment confers unique aspects on how the expression of genes in neurons is regulated. Three salient factors are that (1) neurons are the largest and among the most morphologically complex of all cells, with strict polarity, subcellular compartmentation, and long-distant transport of gene products, signaling molecules, and other materials; (2) information is coded in the temporal firing pattern of membrane depolarization; and (3) neurons must maintain a stable homeostatic level of activation to function so stimuli do not normally drive intracellular signaling to steady state. Each of these factors can require special methods of analysis differing from approaches used in non-neuronal cells. This review considers these three aspects of neuronal gene expression and the current approaches being used to analyze these special features of how the neuronal transcriptome is modulated by action potential firing.

scholarly journals Synaptic and intrinsic plasticity coordinate spike output in cerebellar Purkinje cells

2019 ◽  
Author(s):  
Hyun Geun Shim ◽  
Sang Jeong Kim
Keyword(s):  
Intracellular Signaling ◽  
Synaptic Weight ◽  
Spike Discharge ◽  
Intrinsic Plasticity ◽  
Cerebellar Purkinje Cells ◽  
Dendritic Branches ◽  
The Impact ◽  
Activity Dependent ◽  
Timing Rules

SummaryLearning has been thought to be implemented by activity-dependent modifications of synaptic weight and intrinsic excitability. Here, we highlight how long-term depression at parallel fiber to Purkinje cell synapses (PF-PC LTD) and intrinsic plasticity of PCs coordinate the postsynaptic spike discharge from C57BL/6 male mice. Intrinsic plasticity of PCs in the flocculus matched the timing rules and shared intracellular signaling for PF-PC LTD. Notably, the intrinsic plasticity was confined to the dendritic branches where the synaptic plasticity is formed. Besides, when either synaptic or intrinsic plasticity was impaired, the impact of PF inputs was less reflected by the spike output of PCs. In conclusion, synergies between synaptic and intrinsic plasticity may play a role in tuning the PC output, thereby achieving optimal ranges of output.

SK Channel Regulation of Dendritic Excitability and Dendrodendritic Inhibition in the Olfactory Bulb

2005 ◽  
Vol 94 (6) ◽  
pp. 3743-3750 ◽  
Author(s):  
Brady J. Maher ◽  
Gary L. Westbrook
Keyword(s):  
Olfactory Bulb ◽  
Granule Cells ◽  
Brain Slices ◽  
Mitral Cell ◽  
Mitral Cells ◽  
Sk Channels ◽  
Action Potential Firing ◽  
Sk Channel ◽  
Dendritic Excitability ◽  
Potential Firing

Small-conductance calcium-activated potassium channels (SK) regulate dendritic excitability in many neurons. In the olfactory bulb, regulation of backpropagating action potentials and dendrodendritic inhibition depend on the dendritic excitability of mitral cells. We report here that SK channel currents are present in mitral cells but are not detectable in granule cells in the olfactory bulb. In brain slices from PND 14–21 mice, long step depolarizations (100 ms) in the mitral cell soma evoked a cadmium- and apamin-sensitive outward SK current lasting several hundred milliseconds. Block of the SK current unmasked an inward N-methyl-d-aspartate (NMDA) autoreceptor current due to glutamate released from mitral cell dendrites. In low extracellular Mg2+ (100 μM), brief step depolarizations (2 ms) evoked an apamin-sensitive current that was reduced by d,l-2-amino-5-phosphonopentanoic acid. In current- clamp, block of SK channels increased action potential firing in mitral cells as well as dendrodendritic inhibition. Our results indicate that SK channels can be activated either by calcium channels or NMDA channels in mitral cell dendrites, providing a mechanism for local control of dendritic excitability.

Synaptic integration in a model of cerebellar granule cells

1994 ◽  
Vol 72 (2) ◽  
pp. 999-1009 ◽  
Author(s):  
F. Gabbiani ◽  
J. Midtgaard ◽  
T. Knopfel
Keyword(s):  
Action Potential ◽  
Granule Cell ◽  
Granule Cells ◽  
Mossy Fiber ◽  
Potassium Conductance ◽  
Time Interval ◽  
Synaptic Current ◽  
Action Potential Firing ◽  
Potential Firing ◽  
Kinetics Of

1. We have developed a compartmental model of a turtle cerebellar granule cell consisting of 13 compartmentds that represent the soma and 4 dendrites. We used this model to investigate the synaptic integration of mossy fiber inputs in granule cells. 2. The somatic compartment contained six active ionic conductances: a sodium conductance with fast activation and inactivation kinetics, gNa; a high-voltage-activated calcium conductance, gCa(HVA); a delayed potassium conductance, gK(DR); a transient potassium conductance, gK(A); a slowly relaxing mixed Na+/K+ conductance activating at hyperpolarized membrane potentials, gH, and a calcium- and voltage-dependent potassium conductance, gK(Ca). The kinetics of these conductances was derived from electrophysiological studies in a variety of preparations, including turtle and rat granule cells. 3. In the soma, dynamics of intracellular free Ca2+ was modeled by incorporation of a Na+/Ca2+ exchanger, radial diffusion, and binding sites for Ca2+. 4. The model of the turtle granule cell exhibited depolarization-induced action potential firing with properties closely resembling those seen with intracellular recordings in turtle granule cells in vitro. 5. In the most distal compartments of the dendrites, mossy fiber activity induced synaptic currents mediated by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)- and N-methyl-D-aspartate (NMDA)-type of glutamate receptors. The strength of synaptic inputs chosen was such that the synaptic potential induced by synchronous activation of two mossy fiber synapses reached threshold for induction of a single action potential. 6. The slow time course of the NMDA synaptic current together with the slow relaxation kinetics of gH significantly affected the temporal summation of excitatory synaptic potentials. A priming action potential evoked by mossy fiber stimulation increased the maximal time interval between two synaptic potentials capable to reach again threshold for a subsequent action potential. This time interval then decreased in parallel with the decay of the NMDA synaptic current, reached a minimum after 200 ms, and slowly recovered with reactivation of gH. 7. Repetitive, steady activation of synaptic conductances by a single mossy fiber at different frequencies induced action potential firing with a sharp threshold at 12 Hz. Activity of a single or of several mossy fibers induced firing of the granule cell at a frequency close to that induced when the average synaptic current was directly injected into the cell. The mossy fiber activity-granule cell firing frequency curve was close to linear with a slope of about one-half for input frequencies < or = 400 Hz.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Dynamin phosphorylation controls optimization of endocytosis for brief action potential bursts

eLife ◽  
2013 ◽  
Vol 2 ◽  
Author(s):  
Moritz Armbruster ◽  
Mirko Messa ◽  
Shawn M Ferguson ◽  
Pietro De Camilli ◽  
Timothy A Ryan
Keyword(s):  
Steady State ◽  
Kinetic Parameter ◽  
Action Potential ◽  
Nerve Terminals ◽  
Acceleration Phase ◽  
Action Potential Firing ◽  
Physiological Temperature ◽  
Rich Domain ◽  
Potential Firing ◽  
Activity Dependent

Modulation of synaptic vesicle retrieval is considered to be potentially important in steady-state synaptic performance. Here we show that at physiological temperature endocytosis kinetics at hippocampal and cortical nerve terminals show a bi-phasic dependence on electrical activity. Endocytosis accelerates for the first 15–25 APs during bursts of action potential firing, after which it slows with increasing burst length creating an optimum stimulus for this kinetic parameter. We show that activity-dependent acceleration is only prominent at physiological temperature and that the mechanism of this modulation is based on the dephosphorylation of dynamin 1. Nerve terminals in which dynamin 1 and 3 have been replaced with dynamin 1 harboring dephospho- or phospho-mimetic mutations in the proline-rich domain eliminate the acceleration phase by either setting endocytosis at an accelerated state or a decelerated state, respectively.

scholarly journals Author response: Silent synapses generate sparse and orthogonal action potential firing in adult-born hippocampal granule cells

2017 ◽  
Author(s):  
Liyi Li ◽  
Sébastien Sultan ◽  
Stefanie Heigele ◽  
Charlotte Schmidt-Salzmann ◽  
Nicolas Toni ◽  
...  
Keyword(s):  
Action Potential ◽  
Granule Cells ◽  
Author Response ◽  
Action Potential Firing ◽  
Silent Synapses ◽  
Potential Firing
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