scholarly journals A Thermodynamic Interpretation of the Stimulated Raman Spectroscopic Signature of an Action Potential in a Single Neuron

2020 ◽  
Author(s):  
Shamit Shrivastava ◽  
Hyeon Jeong Lee ◽  
Ji-Xin Cheng
Keyword(s):  
Action Potential ◽  
Single Neuron ◽  
Optical Methods ◽  
Neuronal Membrane ◽  
Raman Spectroscopic ◽  
Thermodynamic State ◽  
Neuronal Membranes ◽  
Membrane Changes ◽  
Stimulated Raman

AbstractIt has previously been suggested that the plasma membrane condenses and melts reversibly during an action potential in a neuron, analogous to an acoustic wave travelling in the compressive membrane region. If true it has fundamental consequences for our understanding of the regulation of biological functions during an action potential. It has long been known that the electrical dipoles in the neuronal membrane reorient during an action potential, observed through a variety of optical methods. However, this information has been insufficient to confirm if and how the collective thermodynamic state of the neuronal membrane changes during an action potential. Here, we show that hyperspectral stimulated Raman spectroscopy (SRS) can resolve the thermodynamic state of the neuronal membranes in a single neuron during an action potential. These measurements indicate that the system becomes ordered and compressed during the de-polarisation phase and disordered and expanded during hyper polarisation Therefore, the observation is consistent with the acoustic hypothesis and SRS provides a powerful tool to not only further validate the hypothesis in future, but also explore the role of membrane thermodynamics during an action potential.

Role of the premature action potential in contractile potentiation: a study of paired stimulation

1972 ◽  
Vol 6 (4) ◽  
pp. 368-374 ◽  
Author(s):  
R. E. EDMANDS ◽  
K. GREENSPAN ◽  
J. C. BAILEY
Keyword(s):  
Action Potential ◽  
Paired Stimulation

scholarly journals Investigations into modifications of neuromuscular physiology by axonal transport disruptions in Drosophila SOD1 mutants

2020 ◽  
Author(s):  
Tristan C. D. G. O’Harrow ◽  
Atsushi Ueda ◽  
Xiaomin Xing ◽  
Chun-Fang Wu
Keyword(s):  
Axonal Transport ◽  
Vital Staining ◽  
Neuronal Membrane ◽  
Adult Lifespan ◽  
Conserved Sequence ◽  
Excitatory Junction Potentials ◽  
Synaptic Boutons ◽  
And Function ◽  
Als Patients

AbstractCu/Zn superoxide dismutase (SOD1) is a cytoplasmic antioxidant enzyme, which, when mutant in humans, is linked to familial cases of the motor neurodegenerative disease amyotrophic lateral sclerosis (ALS). The Drosophila SOD1 gene (Sod) shares a highly conserved sequence with the human homolog, and this study includes examinations of the established hypomorphic n108 allele (Sodn108), alongside a knock-in construct of the G85R allele found in human ALS patients (SodG85R). In addition to previously documented decreased adult lifespan and attenuated motor function, we show that Sod mutant Drosophila can display significant mortality during larval and pupal development. Immunostaining of neuronal membrane at neuromuscular synapses in Sod mutant larvae revealed presynaptic terminals of abnormal morphology, with incompletely segregated and enlarged synaptic boutons along the motor terminal branches, in which vital staining indicated mitochondrial aggregation. We demonstrate strong genetic interactions between SodG85R and the axon transport-linked Pk mutants PkPk and PkSple in larval NMJ morphology and neuromuscular transmission. Intracellular recordings of larval excitatory junction potentials (EJPs) demonstrate enhanced EJP size in the double-mutant of PkPk and SodG85R. To examine synaptic terminal excitability, maintained by Ca2+ channel action and independent of Na+ channel function, we used the NaV blocker TTX, along with the KV1 blocker 4-aminopyridine (4-AP) and the commonly used broad-spectrum K+ channel blocker tetraethylammonium (TEA). We were able to induce prolonged “plateau-like” EJPs, which were further extended in Pk mutants and Pk;Sod double-mutants. These observations were corroborated with focal EJP recording from individual boutons. Altogether, this study highlights alterations in synaptic morphology and function at a developmental stage prior to neurodegeneration and death of Sod mutant organisms, along with a potential role of axonal transport in the maintenance of neuronal health.

The Na+-K+-ATPase α2-subunit isoform modulates contractility in the perinatal mouse diaphragm

2004 ◽  
Vol 287 (5) ◽  
pp. C1300-C1310 ◽  
Author(s):  
Tatiana L. Radzyukevich ◽  
Amy E. Moseley ◽  
Daniel A. Shelly ◽  
Gregory A. Redden ◽  
Michael M. Behbehani ◽  
...  
Keyword(s):  
Action Potential ◽  
Knockout Mice ◽  
Dominant Mode ◽  
Resting Potential ◽  
Force Frequency ◽  
Cellular Functions ◽  
Tetanic Force ◽  
Potential Threshold ◽  
Rate Of Activation

This study uses genetically altered mice to examine the contribution of the Na+-K+-ATPase α2 catalytic subunit to resting potential, excitability, and contractility of the perinatal diaphragm. The α2 protein is reduced by 38% in α2-heterozygous and absent in α2-knockout mice, and α1-isoform is upregulated 1.9-fold in α2-knockout. Resting potentials are depolarized by 0.8–4.0 mV in heterozygous and knockout mice. Action potential threshold, overshoot, and duration are normal. Spontaneous firing, a developmental function, is impaired in knockout diaphragm, but this does not compromise its ability to fire evoked action potential trains, the dominant mode of activation near birth. Maximum tetanic force, rate of activation, force-frequency and force-voltage relationships, and onset and magnitude of fatigue are not changed. The major phenotypic consequence of reduced α2 content is that relaxation from contraction is 1.7-fold faster. This finding reveals a distinct cellular role of the α2-isoform at a step after membrane excitation, which cannot be restored simply by increasing α1 content. Na+/Ca2+ exchanger expression decreases in parallel with α2-isoform, suggesting that Ca2+ extrusion is affected by the altered α2 genotype. There are no major compensatory changes in expression of sarcoplasmic reticulum Ca2+-ATPase, phospholamban, or plasma membrane Ca2+-ATPase. These results demonstrate that the Na+-K+-ATPase α1-isoform alone is able to maintain equilibrium K+ and Na+ gradients and to substitute for α2-isoform in most cellular functions related to excitability and force. They further indicate that the α2-isoform contributes significantly less at rest than expected from its proportional content but can modulate contractility during muscle contraction.

ROLE OF ACTION POTENTIAL SHORTENING IN THE PREVENTION OF ARRHYTHMIAS IN CANINE CARDIAC TISSUE

1999 ◽  
Vol 26 (12) ◽  
pp. 964-969 ◽  
Author(s):  
Kawonia P Mull ◽  
Qadriyyah Debnam ◽  
Syeda M Kabir ◽  
Mohit Lal Bhattacharyya
Keyword(s):  
Action Potential ◽  
Cardiac Tissue ◽  
Action Potential Shortening

Role of NaV1.7 in Action Potential Conduction along Human Bronchial Vagal Afferent C‐fibers

2021 ◽  
Author(s):  
Marian Kollarik ◽  
Fei Ru ◽  
Nikoleta Pavelkova ◽  
John Mulcahy ◽  
John Hunter ◽  
...  
Keyword(s):  
Action Potential ◽  
C Fibers ◽  
Vagal Afferent

Abstract 16953: Role of the Fast Transient Outward Current Ito,f in Shaping Action Potential Waveforms in Human iPSC-derived Cardiomyocytes

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Scott Marrus ◽  
Steven Springer ◽  
Rita Martinez ◽  
Edward Dranoff ◽  
Rebecca Mellor ◽  
...  
Keyword(s):  
Action Potential ◽  
Potassium Current ◽  
Ventricular Myocytes ◽  
Current Clamp ◽  
Transient Outward Potassium Current ◽  
Fast Transient ◽  
Human Ipsc ◽  
Outward Potassium Current ◽  
Upstroke Velocity

Abnormalities of a key repolarizing cardiac potassium current, the fast transient outward potassium current, I to,f , are associated with both heart failure and congenital arrhythmia syndromes. However, the precise role of I to,f in shaping action potential waveforms remains unclear. This study was designed to define the functional role of the fast transient outward potassium current, I to,f , in shaping action potentials in human iPSC-derived cardiomyocytes (iPSC-CMs). Most iPSC-CMs (29 of 43 cells) demonstrated spontaneous electrical activity, slow upstroke velocity (63±71 V/s), a wide range of action potential durations (APD90 = 860±722 ms) and heterogeneous action potential waveforms. Using dynamic current clamp, a modeled human ventricular inwardly rectifying K + current, I K1 , was introduced into iPSC-CMs, resulting in silencing of spontaneous activity, hyperpolarization of the resting membrane potential (RMP = -90±3 mV), increased peak upstroke velocity (dV/dt = 346±71 V/s) and decreased APD90 (420±211 ms) to values similar to those recorded in isolated adult human ventricular myocytes (RMP = -84±3 mV, dV/dt = 348±101 V/s and APD90 = 468±133 ms, all p>0.05). Importantly, a ventricular-like action potential waveform was observed in 25 of the 26 cells studied following the dynamic clamp addition of I K1 . Using these cells as a model of human ventricular myocytes, further dynamic current clamp experiments introduced a modeled human fast transient outward K + current, I to,f , and revealed that increasing in the amplitude of I to,f results in an increase in the phase 1 notch and a progressive shortening of the action potential duration in iPSC-CMs. Together, the experiments here demonstrate that combining human iPSC-CMs with the power of the dynamic current clamp technique to modulate directly and precisely the “expression” of individual ionic currents provides a novel and quantitative approach to defining the roles of specific ionic conductances in regulating the excitability of human cardiomyocytes.

Transmembrane potentials and fluxes in isolated rabbit atria

1959 ◽  
Vol 196 (6) ◽  
pp. 1292-1296 ◽  
Author(s):  
R. L. Klein ◽  
W. C. Holland
Keyword(s):  
Action Potential ◽  
Active Transport ◽  
Terminal Phase ◽  
Transmembrane Potentials ◽  
Unidirectional Fluxes ◽  
Rabbit Atria

Data are presented from a study of transmembrane potentials and unidirectional fluxes of K42 under identical conditions in isolated rabbit atria. The effects of acetylcholine and varying extracellular concentrations of Na, K and Ca were investigated. Particular emphasis has been placed on the role of Ca and on the terminal phase of repolarization of the action potential, namely the negative after potential. Data are given which support the contention that the duration of the negative after potential depends on an active transport of K or Na, or both.

Resting and Active Properties of Pyramidal Neurons in Subiculum and CA1 of Rat Hippocampus

2000 ◽  
Vol 84 (5) ◽  
pp. 2398-2408 ◽  
Author(s):  
Nathan P. Staff ◽  
Hae-Yoon Jung ◽  
Tara Thiagarajan ◽  
Michael Yao ◽  
Nelson Spruston
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Pyramidal Neurons ◽  
Current Injection ◽  
Synaptic Integration ◽  
Membrane Properties ◽  
Neuronal Membrane ◽  
Similar Action ◽  
Ca1 Neurons ◽  
Ca1 Pyramidal Neurons

Action potentials are the end product of synaptic integration, a process influenced by resting and active neuronal membrane properties. Diversity in these properties contributes to specialized mechanisms of synaptic integration and action potential firing, which are likely to be of functional significance within neural circuits. In the hippocampus, the majority of subicular pyramidal neurons fire high-frequency bursts of action potentials, whereas CA1 pyramidal neurons exhibit regular spiking behavior when subjected to direct somatic current injection. Using patch-clamp recordings from morphologically identified neurons in hippocampal slices, we analyzed and compared the resting and active membrane properties of pyramidal neurons in the subiculum and CA1 regions of the hippocampus. In response to direct somatic current injection, three subicular firing types were identified (regular spiking, weak bursting, and strong bursting), while all CA1 neurons were regular spiking. Within subiculum strong bursting neurons were found preferentially further away from the CA1 subregion. Input resistance ( R N), membrane time constant (τm), and depolarizing “sag” in response to hyperpolarizing current pulses were similar in all subicular neurons, while R N and τm were significantly larger in CA1 neurons. The first spike of all subicular neurons exhibited similar action potential properties; CA1 action potentials exhibited faster rising rates, greater amplitudes, and wider half-widths than subicular action potentials. Therefore both the resting and active properties of CA1 pyramidal neurons are distinct from those of subicular neurons, which form a related class of neurons, differing in their propensity to burst. We also found that both regular spiking subicular and CA1 neurons could be transformed into a burst firing mode by application of a low concentration of 4-aminopyridine, suggesting that in both hippocampal subfields, firing properties are regulated by a slowly inactivating, D-type potassium current. The ability of all subicular pyramidal neurons to burst strengthens the notion that they form a single neuronal class, sharing a burst generating mechanism that is stronger in some cells than others.

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