High Safety Factor for Action Potential Conduction Along Axons But Not Dendrites of Cultured Hippocampal and Cortical Neurons

1998 ◽  
Vol 80 (4) ◽  
pp. 2089-2101 ◽  
Author(s):  
Paul J. Mackenzie ◽  
Timothy H. Murphy
Keyword(s):  
Action Potential ◽  
Safety Factor ◽  
Cortical Neurons ◽  
Neuronal Firing ◽  
Repetitive Firing ◽  
Current Clamp ◽  
Similar Reduction ◽  
Axonal Conduction ◽  
Cultured Cortical Neurons ◽  
20 Nm

Mackenzie, Paul J. and Timothy H. Murphy. High safety factor for action potential conduction along axons but not dendrites of cultured hippocampal and cortical neurons. J. Neurophysiol. 80: 2089–2101, 1998. By using a combination of Ca2+ imaging and current-clamp recording, we previously reported that action potential (AP) conduction is reliably observed from the soma to axonal terminals in cultured cortical neurons. To extend these studies, we evaluated Ca2+ influx evoked by Na+ APs as a marker of AP conduction under conditions that are expected to lower the conduction safety factor to explore mechanisms of axonal and dendritic excitability. As expected, reducing the extracellular Na+ concentration from 150 to ∼60 mM decreased the amplitude of APs recorded in the soma but surprisingly did not influence axonal conduction, as monitored by measuring Ca2+ transients. Furthermore, reliable axonal conduction was observed in dilute (20 nM) tetrodotoxin (TTX), despite a similar reduction in AP amplitude. In contrast, the Ca2+ transient measured along dendrites was markedly reduced in low Na+, although still mediated by TTX-sensitive Na+ channels. Dendritic action-potential evoked Ca2+ transients were also markedly reduced in 20 nM TTX. These data provide further evidence that strongly excitable axons are functionally compartmentalized from weakly excitable dendrites. We conclude that modulation of Na+ currents or membrane potential by neurotransmitters or repetitive firing is more likely to influence neuronal firing before AP generation than the propagation of signals to axonal terminals. In contrast, the relatively low safety factor for back-propagating APs in dendrites would suggest a stronger effect of Na+ current modulation.

scholarly journals Characterization of Na+-Activated K+ Currents in Larval Lamprey Spinal Cord Neurons

2007 ◽  
Vol 97 (5) ◽  
pp. 3484-3493 ◽  
Author(s):  
Dietmar Hess ◽  
Evanthia Nanou ◽  
Abdeljabbar El Manira
Keyword(s):  
Spinal Cord ◽  
Action Potential ◽  
Feedback Mechanism ◽  
Neuronal Firing ◽  
Repetitive Firing ◽  
Spinal Cord Neurons ◽  
Negative Feedback Mechanism ◽  
Synaptic Interactions ◽  
Action Potential Waveform

Potassium channels play an important role in controlling neuronal firing and synaptic interactions. Na+-activated K+ ( KNa) channels have been shown to exist in neurons in different regions of the CNS, but their physiological function has been difficult to assess. In this study, we have examined if neurons in the spinal cord possess KNa currents. We used whole cell recordings from isolated spinal cord neurons in lamprey. These neurons display two different KNa currents. The first was transient and activated by the Na+ influx during the action potentials, and it was abolished when Na+ channels were blocked by tetrodotoxin. The second KNa current was sustained and persisted in tetrodotoxin. Both KNa currents were abolished when Na+ was substituted with choline or N-methyl-d-glucamine, indicating that they are indeed dependent on Na+ influx into neurons. When Na+ was substituted with Li+, the amplitude of the inward current was unchanged, whereas the transient KNa current was reduced but not abolished. This suggests that the transient KNa current is partially activated by Li+. These two KNa currents have different roles in controlling the action potential waveform. The transient KNa appears to act as a negative feedback mechanism sensing the Na+ influx underlying the action potential and may thus be critical for setting the amplitude and duration of the action potential. The sustained KNa current has a slow kinetic of activation and may underlie the slow Ca2+-independent afterhyperpolarization mediated by repetitive firing in lamprey spinal cord neurons.

Mechanical perturbation of cultured cortical neurons reveals a stretch-induced delayed depolarization

1995 ◽  
Vol 74 (6) ◽  
pp. 2767-2773 ◽  
Author(s):  
S. J. Tavalin ◽  
E. F. Ellis ◽  
L. S. Satin
Keyword(s):  
Brain Injury ◽  
Cortical Neurons ◽  
Receptor Activation ◽  
Neuronal Firing ◽  
Neonatal Rat ◽  
Resting Membrane Potential ◽  
Cell Stretch ◽  
Cultured Cortical Neurons ◽  
Rat Cortical Neurons

1. An in vitro cellular model of injury was used to elucidate mechanisms contributing to traumatic brain injury (TBI). Neonatal rat cortical neurons cultured on a flexible silastic membrane were stretched rapidly and reversibly by a 50-ms pulse of pressurized air. 2. Sublethal cell stretch depolarized neuronal resting membrane potential by approximately 10 mV but only if cells were incubated for 1 h after injury. Stretch-induced delayed depolarization (or SIDD) returned to baseline values within 24 h. 3. SIDD was dependent on the degree of cell stretch and required neuronal firing, calcium entry, and N-methyl-D-aspartate receptor activation for its induction but not its maintainance. 4. Similarities between SIDD and TBI suggest that SIDD may play a role in brain injury.

scholarly journals Nicotinic modulation of Ca2+ oscillations in rat cortical neurons in vitro

2016 ◽  
Vol 310 (9) ◽  
pp. C748-C754 ◽  
Author(s):  
JianGang Wang ◽  
YaLi Wang ◽  
FangLi Guo ◽  
ZhiBo Feng ◽  
XiangFang Wang ◽  
...  
Keyword(s):  
Nicotinic Acetylcholine Receptors ◽  
Cortical Neurons ◽  
Oscillation Frequency ◽  
Acetylcholine Receptors ◽  
Nicotinic Acetylcholine ◽  
Cultured Cortical Neurons ◽  
Intracellular Ca ◽  
Rat Cortical Neurons ◽  
20 Nm

The roles of nicotine on Ca2+ oscillations [intracellular Ca2+ ([Ca2+]i) oscillation] in rat primary cultured cortical neurons were studied. The spontaneous [Ca2+]i oscillations (SCO) were recorded in a portion of the neurons (65%) cultured for 7–10 days in vitro. Application of nicotine enhanced [Ca2+]i oscillation frequency and amplitude, which were reduced by the selective α4β2-nicotinic acetylcholine receptors (nAChRs) antagonist dihydro-β-erythroidine (DHβE) hydrobromide, and the selective α7-nAChRs antagonist methyllycaconitine citrate (MLA, 20 nM). DHβE reduced SCO frequency and prevented the nicotinic increase in the frequency. DHβE somewhat enhanced SCO amplitude and prevented nicotinic increase in the amplitude. MLA (20 nM) itself reduced SCO frequency without affecting the amplitude but blocked nicotinic increase in [Ca2+]i oscillation frequency and amplitude. Furthermore, coadministration of both α4β2- and α7-nAChRs antagonists completely prevented nicotinic increment in [Ca2+]i oscillation frequency and amplitude. Thus, our results indicate that both α4β2- and α7-nAChRs mediated nicotine-induced [Ca2+]i oscillations, and two nAChR subtypes differentially regulated SCO.

Presenilin 1 Deficiency Alters the Activity of Voltage-Gated Ca2+ Channels in Cultured Cortical Neurons

2005 ◽  
Vol 94 (6) ◽  
pp. 4421-4429 ◽  
Author(s):  
David G. Cook ◽  
Xiaofan Li ◽  
Sheree D. Cherry ◽  
Angela R. Cantrell
Keyword(s):  
Cortical Neurons ◽  
Critical Role ◽  
Neuronal Firing ◽  
Voltage Gated ◽  
Voltage Dependent ◽  
Cultured Cortical Neurons ◽  
Intracellular Ca ◽  
Multiple Levels ◽  
P Type ◽  
Ca2 Channels

Presenilins 1 and 2 (PS1 and PS2, respectively) play a critical role in mediating γ-secretase cleavage of the amyloid precursor protein (APP). Numerous mutations in the presenilins are known to cause early-onset familial Alzheimer's disease (FAD). In addition, it is well established that PS1 deficiency leads to altered intracellular Ca2+ homeostasis involving endoplasmic reticulum Ca2+ stores. However, there has been little evidence suggesting Ca2+ signals from extracellular sources are influenced by PS1. Here we report that the Ca2+ currents carried by voltage-dependent Ca2+ channels are increased in PS1-deficient cortical neurons. This increase is mediated by a significant increase in the contributions of L- and P-type Ca2+ channels to the total voltage-mediated Ca2+ conductance in PS1 (−/−) neurons. In addition, chelating intracellular Ca2+ with 1,2-bis-( o-aminophenoxy)ethane- N,N,N′,N′-tetraacetic acid (BAPTA) produced an increase in Ca2+ current amplitude that was comparable to the increase caused by PS1 deficiency. In contrast to this, BAPTA had no effect on voltage-dependent Ca2+ conductances in PS1-deficient neurons. These data suggest that PS1 deficiency may influence voltage-gated Ca2+ channel function by means that involve intracellular Ca2+ signaling. These findings reveal that PS1 functions at multiple levels to regulate and stabilize intracellular Ca2+ levels that ultimately control neuronal firing behavior and influence synaptic transmission.

Role of Voltage-Gated K+ Currents in Mediating the Regular-Spiking Phenotype of Callosal-Projecting Rat Visual Cortical Neurons

1997 ◽  
Vol 78 (5) ◽  
pp. 2321-2335 ◽  
Author(s):  
Rachel E. Locke ◽  
Jeanne M. Nerbonne
Keyword(s):  
Action Potential ◽  
Cortical Neurons ◽  
Action Potentials ◽  
Repetitive Firing ◽  
Functional Roles ◽  
Firing Rates ◽  
Voltage Gated ◽  
Firing Properties ◽  
Visual Cortical

Locke, Rachel E. and Jeanne M. Nerbonne. Role of voltage-gated K+ currents in mediating the regular-spiking phenotype of callosal-projecting rat visual cortical neurons. J. Neurophysiol. 78: 2321–2335, 1997. Whole cell current- and voltage-clamp recordings were combined to examine action potential waveforms, repetitive firing patterns, and the functional roles of voltage-gated K+ currents ( I A, I D, and I K) in identified callosal-projecting (CP) neurons from postnatal (day 7–13) rat primary visual cortex. Brief (1 ms) depolarizing current injections evoke single action potentials in CP neurons with mean ± SD ( n = 60) durations at 50 and 90% repolarization of 1.9 ± 0.5 and 5.5 ± 2.0 ms, respectively; action potential durations in individual cells are correlated inversely with peak outward current density. During prolonged threshold depolarizing current injections, CP neurons fire repetitively, and two distinct, noninterconverting “regular-spiking” firing patterns are evident: weakly adapting CP cells fire continuously, whereas strongly adapting CP cells cease firing during maintained depolarizing current injections. Action potential repolarization is faster and afterhyperpolarizations are more pronounced in strongly than in weakly adapting CP cells. In addition, input resistances are lower and plateau K+ current densities are higher in strongly than in weakly adapting CP cells. Functional studies reveal that blockade of I D reduces the latency to firing an action potential, and increases action potential durations at 50 and 90% repolarization. Blockade of I D also increases firing rates in weakly adapting cells and results in continuous firing of strongly adapting cells. After applications of millimolar concentrations of 4-aminopyridine to suppress I A (as well as block I D), action potential durations at 50 and 90% repolarization are further increased, and firing rates are accelerated over those observed when only I D is blocked. Using VClamp/CClamp and the voltage-clamp data in the preceding paper, mathematical descriptions of I A, I D, and I K are generated and a model of the electrophysiological properties of rat visual cortical CP neurons is developed. The model is used to simulate the firing properties of strongly adapting and weakly adapting CP cells and to explore the functional roles of I A, I D, and I K in shaping the waveforms of individual action potentials and controlling the repetitive firing properties of these cells.

scholarly journals The Bacterial Enzyme Cas13 Interferes with Neurite Outgrowth from Cultured Cortical Neurons

Toxins ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 262
Author(s):  
Qin-Wei Wu ◽  
Josef P. Kapfhammer
Keyword(s):  
Rna Editing ◽  
Cortical Neurons ◽  
High Efficiency ◽  
Primary Cultures ◽  
Cultured Neurons ◽  
Therapeutic Tool ◽  
Bacterial Enzyme ◽  
Rna Targeting ◽  
Cultured Cortical Neurons ◽  
New Generation

The CRISPR-Cas13 system based on a bacterial enzyme has been explored as a powerful new method for RNA manipulation. Due to the high efficiency and specificity of RNA editing/interference achieved by this system, it is currently being developed as a new therapeutic tool for the treatment of neurological and other diseases. However, the safety of this new generation of RNA therapies is still unclear. In this study, we constructed a vector expressing CRISPR-Cas13 under a constitutive neuron-specific promoter. CRISPR-Cas13 from Leptotrichia wadei was expressed in primary cultures of mouse cortical neurons. We found that the presence of CRISPR-Cas13 impedes the development of cultured neurons. These results show a neurotoxic action of Cas13 and call for more studies to test for and possibly mitigate the toxic effects of Cas13 enzymes in order to improve CRISPR-Cas13-based tools for RNA targeting.

scholarly journals Curbing action potential generation or ATP-synthase leads to a decrease in in-cell pyruvate dehydrogenase activity in rat cerebrum slices

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Benjamin Grieb ◽  
Sivaranjan Uppala ◽  
Gal Sapir ◽  
David Shaul ◽  
J. Moshe Gomori ◽  
...  
Keyword(s):  
Action Potential ◽  
Atp Synthase ◽  
Neural Activity ◽  
Pyruvate Dehydrogenase ◽  
Cerebral Metabolism ◽  
Neuronal Firing ◽  
Action Potential Generation ◽  
Potential Generation ◽  
Drastic Increase ◽  
Rat Cerebrum

AbstractDirect and real-time monitoring of cerebral metabolism exploiting the drastic increase in sensitivity of hyperpolarized 13C-labeled metabolites holds the potential to report on neural activity via in-cell metabolic indicators. Here, we followed the metabolic consequences of curbing action potential generation and ATP-synthase in rat cerebrum slices, induced by tetrodotoxin and oligomycin, respectively. The results suggest that pyruvate dehydrogenase (PDH) activity in the cerebrum is 4.4-fold higher when neuronal firing is unperturbed. The PDH activity was 7.4-fold reduced in the presence of oligomycin, and served as a pharmacological control for testing the ability to determine changes to PDH activity in viable cerebrum slices. These findings may open a path towards utilization of PDH activity, observed by magnetic resonance of hyperpolarized 13C-labeled pyruvate, as a reporter of neural activity.

Abstract 91: Remodeling After Stroke: The Recovering Brain Is Vulnerable To Lipoxygenase-dependent Semaphorin Signaling

Stroke ◽  
2013 ◽  
Vol 44 (suppl_1) ◽  
Author(s):  
Anton Pekcec ◽  
Kazim Yigitkanli ◽  
Joo Eun Jung ◽  
Hulya Karatas ◽  
Eng H Lo ◽  
...  
Keyword(s):  
Knockout Mice ◽  
Cortical Neurons ◽  
Second Messengers ◽  
Artery Occlusion ◽  
Tube Formation ◽  
Stroke Recovery ◽  
Experimental Stroke ◽  
Axon Extension ◽  
Cultured Cortical Neurons ◽  
Cerebral Artery Occlusion

Background and Purpose— Recovery from stroke is limited in part by an inhibitory environment in the post-ischemic brain, but factors preventing successful remodeling are not well known. We sought to investigate if signaling from the axon guidance molecule semaphorin 3A (Sema3A) via eicosanoid second messengers can contribute to this inhibitory environment, and if blocking the Sema3A pathway can provide a benefit following experimental stroke. Methods— Cultured cortical neurons from mice were treated with recombinant Sema3A, or with the eicosanoids 12-HETE and 12-HPETE. Neurons from ALOX15 knockout mice, and a human brain endothelial cell line, were treated similarly. The filament model of MCAO was used to induce experimental stroke in mice, in some of which Sema3A was injected stereotactically into the striatum. The 12/15-LOX inhibitor LOXBlock-1 was injected intraperitoneally one week after MCAO. Results— Expression levels of 12/15-lipoxygenase (12/15-LOX) were increased within two hours after exposure of primary neurons to 90nM recombinant Sema3A. Either Sema3A, or the 12/15-lipoxygenase (12/15-LOX) metabolites 12-HETE and 12-HPETE at 300nM, blocked axon extension in neurons compared to solvent controls, and decreased tube formation in endothelial cells. The Sema3A effect was reversed by inhibiting 12/15-LOX, and neurons derived from 12/15-LOX knockout mice were insensitive to Sema3A. Following middle cerebral artery occlusion to induce stroke in mice, immunohistochemistry showed both Sema3A and 12/15-LOX are increased in the cortex up to two weeks. To determine if a Sema3A-dependent damage pathway is activated following ischemia, we injected recombinant Sema3A into the striatum. Sema3A alone did not cause injury in normal brains. But when injected into post-ischemic brains, Sema3A increased cortical damage by 79%, and again this effect was reversed by 12/15-LOX inhibition. Administration of the 12/15-LOX inhibitor LOXBlock-1 7 days after transient MCAO increased vascularization in the infarcted and peri-infarct area one week later. Conclusions— Our findings suggest that blocking the semaphorin pathway may provide a novel therapeutic strategy to improve stroke recovery.

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