Distribution of Acid Sensing Ion Channels in Axonal Growth Cones and Presynaptic Membrane of Cultured Hippocampal Neurons

Extracellular acidification has been shown to generate action potentials (APs) in several types of neurons. In this study, we investigated the role of acid-sensing ion channels (ASICs) in acid-induced AP generation in brain neurons. ASICs are neuronal Na+ channels that belong to the epithelial Na+ channel/degenerin family and are transiently activated by a rapid drop in extracellular pH. We compared the pharmacological and biophysical properties of acid-induced AP generation with those of ASIC currents in cultured hippocampal neurons. Our results show that acid-induced AP generation in these neurons is essentially due to ASIC activation. We demonstrate for the first time that the probability of inducing APs correlates with current entry through ASICs. We also show that ASIC activation in combination with other excitatory stimuli can either facilitate AP generation or inhibit AP bursts, depending on the conditions. ASIC-mediated generation and modulation of APs can be induced by extracellular pH changes from 7.4 to slightly <7. Such local extracellular pH values may be reached by pH fluctuations due to normal neuronal activity. Furthermore, in the plasma membrane, ASICs are localized in close proximity to voltage-gated Na+ and K+ channels, providing the conditions necessary for the transduction of local pH changes into electrical signals.

Download Full-text

Acid-sensing ion channels regulate spontaneous inhibitory activity in the hippocampus: possible implications for epilepsy

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2015.0431 ◽

2016 ◽

Vol 371 (1700) ◽

pp. 20150431 ◽

Cited By ~ 13

Author(s):

O. Ievglevskyi ◽

D. Isaev ◽

O. Netsyk ◽

A. Romanov ◽

M. Fedoriuk ◽

...

Keyword(s):

Ion Channels ◽

Hippocampal Neurons ◽

Hippocampal Slices ◽

Synaptic Activity ◽

Mammalian Brain ◽

Strong Increase ◽

Life And Death ◽

Acid Sensing Ion Channels

Acid-sensing ion channels (ASICs) play an important role in numerous functions in the central and peripheral nervous systems ranging from memory and emotions to pain. The data correspond to a recent notion that each neuron and many glial cells of the mammalian brain express at least one member of the ASIC family. However, the mechanisms underlying the involvement of ASICs in neuronal activity are poorly understood. However, there are two exceptions, namely, the straightforward role of ASICs in proton-based synaptic transmission in certain brain areas and the role of the Ca 2+ -permeable ASIC1a subtype in ischaemic cell death. Using a novel orthosteric ASIC antagonist, we have found that ASICs specifically control the frequency of spontaneous inhibitory synaptic activity in the hippocampus. Inhibition of ASICs leads to a strong increase in the frequency of spontaneous inhibitory postsynaptic currents. This effect is presynaptic because it is fully reproducible in single synaptic boutons attached to isolated hippocampal neurons. In concert with this observation, inhibition of the ASIC current diminishes epileptic discharges in a low Mg 2+ model of epilepsy in hippocampal slices and significantly reduces kainate-induced discharges in the hippocampus in vivo . Our results reveal a significant novel role for ASICs. This article is part of the themed issue ‘Evolution brings Ca 2+ and ATP together to control life and death’.

Download Full-text

Delayed Retraction of Filopodia in Gelsolin Null Mice

The Journal of Cell Biology ◽

10.1083/jcb.138.6.1279 ◽

1997 ◽

Vol 138 (6) ◽

pp. 1279-1287 ◽

Cited By ~ 105

Author(s):

Mei Lu ◽

Walter Witke ◽

David J. Kwiatkowski ◽

Kenneth S. Kosik

Keyword(s):

Growth Cone ◽

Hippocampal Neurons ◽

Neurite Growth ◽

Time Lapse ◽

Growth Cones ◽

Wild Type ◽

Dynamic Studies ◽

Shape Changes ◽

Time Lapse Video ◽

Cultured Hippocampal Neurons

Growth cones extend dynamic protrusions called filopodia and lamellipodia as exploratory probes that signal the direction of neurite growth. Gelsolin, as an actin filament-severing protein, may serve an important role in the rapid shape changes associated with growth cone structures. In wild-type (wt) hippocampal neurons, antibodies against gelsolin labeled the neurite shaft and growth cone. The behavior of filopodia in cultured hippocampal neurons from embryonic day 17 wt and gelsolin null (Gsn−) mice (Witke, W., A.H. Sharpe, J.H. Hartwig, T. Azuma, T.P. Stossel, and D.J. Kwiatkowski. 1995. Cell. 81:41–51.) was recorded with time-lapse video microscopy. The number of filopodia along the neurites was significantly greater in Gsn− mice and gave the neurites a studded appearance. Dynamic studies suggested that most of these filopodia were formed from the region of the growth cone and remained as protrusions from the newly consolidated shaft after the growth cone advanced. Histories of individual filopodia in Gsn− mice revealed elongation rates that did not differ from controls but an impaired retraction phase that probably accounted for the increased number of filopodia long the neutrite shaft. Gelsolin appears to function in the initiation of filopodial retraction and in its smooth progression.

Download Full-text

B-50/GAP43 localization on membranes of putative transport vesicle in the cell body, neurites and growth cones of cultured hippocampal neurons

Neuroscience Letters ◽

10.1016/0304-3940(92)90314-w ◽

1992 ◽

Vol 137 (1) ◽

pp. 129-132 ◽

Cited By ~ 13

Author(s):

M.Van Lookeren Campagne ◽

C.G. Dotti ◽

A.J. Verkleij ◽

W.H. Gispen ◽

A.B. Oestreicher

Keyword(s):

Cell Body ◽

Hippocampal Neurons ◽

Growth Cones ◽

Transport Vesicle ◽

Cultured Hippocampal Neurons

Download Full-text

Functional NMDA Receptors at Axonal Growth Cones of Young Hippocampal Neurons

Journal of Neuroscience ◽

10.1523/jneurosci.5639-10.2011 ◽

2011 ◽

Vol 31 (25) ◽

pp. 9289-9297 ◽

Cited By ~ 23

Author(s):

P. Y. Wang ◽

R. S. Petralia ◽

Y.-X. Wang ◽

R. J. Wenthold ◽

S. D. Brenowitz

Keyword(s):

Nmda Receptors ◽

Hippocampal Neurons ◽

Axonal Growth ◽

Growth Cones

Download Full-text

Unique Responses of Differentiating Neuronal Growth Cones to Inhibitory Cues Presented by Oligodendrocytes

The Journal of Cell Biology ◽

10.1083/jcb.142.1.191 ◽

1998 ◽

Vol 142 (1) ◽

pp. 191-202 ◽

Cited By ~ 19

Author(s):

A. Shibata ◽

M.V. Wright ◽

S. David ◽

L. McKerracher ◽

P.E. Braun ◽

...

Keyword(s):

Growth Cone ◽

Hippocampal Neurons ◽

Dendritic Growth ◽

System Development ◽

Axonal Growth ◽

Growth Cones ◽

Nervous System Development ◽

Environmental Cues ◽

Growth Cone Collapse ◽

Neuronal Growth Cones

During central nervous system development, neurons differentiate distinct axonal and dendritic processes whose outgrowth is influenced by environmental cues. Given the known intrinsic differences between axons and dendrites and that little is known about the response of dendrites to inhibitory cues, we tested the hypothesis that outgrowth of differentiating axons and dendrites of hippocampal neurons is differentially influenced by inhibitory environmental cues. A sensitive growth cone behavior assay was used to assess responses of differentiating axonal and dendritic growth cones to oligodendrocytes and oligodendrocyte- derived, myelin-associated glycoprotein (MAG). We report that >90% of axonal growth cones collapsed after contact with oligodendrocytes. None of the encounters between differentiating, MAP-2 positive dendritic growth cones and oligodendrocytes resulted in growth cone collapse. The insensitivity of differentiating dendritic growth cones appears to be acquired since they develop from minor processes whose growth cones are inhibited (nearly 70% collapse) by contact with oligodendrocytes. Recombinant MAG(rMAG)-coated beads caused collapse of 72% of axonal growth cones but only 29% of differentiating dendritic growth cones. Unlike their response to contact with oligodendrocytes, few growth cones of minor processes were inhibited by rMAG-coated beads (20% collapsed). These results reveal the capability of differentiating growth cones of the same neuron to partition the complex molecular terrain they navigate by generating unique responses to particular inhibitory environmental cues.

Download Full-text

Pregnenolone Sulfate Activates NMDA Receptor Channels

Physiological Research ◽

10.33549/physiolres.932558 ◽

2013 ◽

pp. 731-736 ◽

Cited By ~ 5

Author(s):

E. ADAMUSOVÁ ◽

O. CAIS ◽

V. VYKLICKÝ ◽

E. KUDOVÁ ◽

H. CHODOUNSKÁ ◽

...

Keyword(s):

Synaptic Plasticity ◽

Ion Channels ◽

Nmda Receptor ◽

Calcium Signaling ◽

Hippocampal Neurons ◽

Hek293 Cells ◽

Independent Effect ◽

Pregnenolone Sulfate ◽

Specific Manner ◽

Cultured Hippocampal Neurons

Pregnenolone sulfate (PS), an endogenously occurring neurosteroid, has been shown to modulate the activity of several neurotransmitter-gated channels, including the NMDA receptor (NMDAR). NMDARs are glutamate-gated ion channels involved in excitatory synaptic transmission, synaptic plasticity, and excitotoxicity. In this study, we analyzed the effects of PS on calcium signaling in cultured hippocampal neurons and HEK293 cells expressing NMDAR. The cells were loaded with the Ca2+ sensor Fura-2. In agreement with previous electrophysiological experiments, PS potentiated the increases in intracellular Ca2+ induced by an exogenous application of glutamate; however, PS also increased intracellular Ca2+ in the absence of exogenous NMDA agonist. The agonist-independent effect of PS was induced in all neurons studied and in HEK293 cells expressing GluN1/GluN2A-B receptors in a neurosteroid-specific manner. We conclude that PS is an endogenous NMDA agonist that activates the GluN1/GluN2A-B receptors.

Download Full-text