Motor patterning, ion regulation and Spreading Depolarization during CNS shutdown induced by experimental anoxia in Locusta migratoria.

Mapping Intimacies ◽

10.1101/2021.05.12.443850 ◽

2021 ◽

Author(s):

Mel Robertson ◽

Rachel A Van Dusen

Keyword(s):

Locusta Migratoria ◽

Water Immersion ◽

Ion Homeostasis ◽

Membrane Conductance ◽

Cell Swelling ◽

Neuronal Membrane ◽

Muscle Fibres ◽

Ion Regulation ◽

Tracheal System ◽

Spreading Depolarization

Anoxia induces a reversible coma in insects. Coma onset is triggered by the arrest of mechanisms responsible for maintaining membrane ion homeostasis in the CNS, resulting in a wave of neuronal and glial depolarization known as spreading depolarization (SD). Different methods of anoxia influence the behavioural response but their effects on SD are unknown. We investigated the effects of CO2, N2, and H2O on the characteristics of coma induction and recovery in Locusta migratoria. Water immersion delayed coma onset and recovery, likely due to involvement of the tracheal system and the nature of asphyxiation but otherwise resembled N2 delivery. The main difference between N2 and CO2 was that CO2 hastened onset of neural failure and SD and delayed recovery. In the CNS, this was associated with CO2 inducing an abrupt and immediate decrease of interstitial pH and increase of extracellular [K+]. Recording of the transperineurial potential showed that SD propagation and a postanoxic negativity (PAN) were similar with both gases. The PAN increased with ouabain treatment, likely due to removal of the counteracting electrogenic effect of Na+/K+-ATPase, and was inhibited by bafilomycin, a proton pump inhibitor, suggesting that it was generated by the electrogenic effect of a Vacuolar-type ATPase (VA). Muscle fibres depolarized by ~20 mV, which happened more rapidly with CO2 compared with N2. Wing muscle motoneurons depolarized nearly completely in two stages, with CO2 causing more rapid onset and slower recovery than N2. Other parameters of SD onset and recovery were similar with the two gases. Electrical resistance across the ganglion sheath increased during anoxia and at SD onset. We provisionally attribute this to cell swelling reducing the dimensions of the interstitial pathway from neuropil to the bathing saline. Neuronal membrane resistance decreased abruptly at SD onset indicating opening of an unidentified membrane conductance. Consideration of the intracellular recording relative to the saline suggests that the apical membrane of perineurial glia depolarizes prior to neuron depolarization. We propose that SD is triggered by events at the perineurial sheath and then propagates laterally and more deeply into the neuropil. We conclude that the fundamental nature of SD is not dependent on the method of anoxia however the timing of onset and recovery are influenced; water immersion is complicated by the tracheal system and CO2 delivery has more rapid and longer lasting effects, associated with severe interstitial acidosis.

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Motor patterning, ion regulation and spreading depolarization during CNS shutdown induced by experimental anoxia in Locusta migratoria

Comparative Biochemistry and Physiology Part A Molecular & Integrative Physiology ◽

10.1016/j.cbpa.2021.111022 ◽

2021 ◽

pp. 111022

Author(s):

R. Meldrum Robertson ◽

Rachel A. Van Dusen

Keyword(s):

Locusta Migratoria ◽

Ion Regulation ◽

Spreading Depolarization

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Inhibition of ATP-sensitive potassium channels exacerbates anoxic coma in Locusta migratoria

Journal of Neurophysiology ◽

10.1152/jn.00379.2020 ◽

2020 ◽

Vol 124 (6) ◽

pp. 1754-1765

Author(s):

Rachel A. Van Dusen ◽

Hannah Shuster-Hyman ◽

R. Meldrum Robertson

Keyword(s):

Potassium Channels ◽

Blood Brain Barrier ◽

Locusta Migratoria ◽

Ion Homeostasis ◽

Brain Barrier ◽

Spreading Depolarization ◽

Blood Brain ◽

Channel Inhibition ◽

Anoxic Coma

We demonstrate the involvement of ATP-sensitive K+ (KATP) channels during recovery from spreading depolarization (SD) induced via anoxic coma in locusts. KATP inhibition using glybenclamide impaired ion homeostasis across the blood-brain barrier, resulting in a longer time to recovery of transperineurial potential following SD. Comparison with ouabain indicates that the effects of glybenclamide are not mediated by the Na+/K+-ATPase but are a result of KATP channel inhibition.

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Exhaled Breath Condensate Detects Baseline Reductions in Chloride and Increases in Response to Albuterol in Cystic Fibrosis Patients

Clinical Medicine Insights Circulatory Respiratory and Pulmonary Medicine ◽

10.4137/ccrpm.s12882 ◽

2013 ◽

Vol 7 ◽

pp. CCRPM.S12882 ◽

Cited By ~ 2

Author(s):

Courtney M. Wheatley ◽

Wayne J. Morgan ◽

Nicholas A. Cassuto ◽

William T. Foxx-Lupo ◽

Cori L. Daines ◽

...

Keyword(s):

Cystic Fibrosis ◽

Exhaled Breath Condensate ◽

Ionic Composition ◽

Membrane Conductance ◽

Pharmacological Therapy ◽

Exhaled Breath ◽

Ion Regulation ◽

Capillary Blood Volume ◽

Pulmonary Capillary Blood ◽

Breath Condensate

Impaired ion regulation and dehydration is the primary pathophysiology in cystic fibrosis (CF) lung disease. A potential application of exhaled breath condensate (EBC) collection is to assess airway surface liquid ionic composition at baseline and in response to pharmacological therapy in CF. Our aims were to determine if EBC could detect differences in ion regulation between CF and healthy and measure the effect of the albuterol on EBC ions in these populations. Baseline EBC Cl−, DLCO and SpO2 were lower in CF (n = 16) compared to healthy participants (n = 16). EBC Cl− increased in CF subjects, while there was no change in DLCO or membrane conductance, but a decrease in pulmonary-capillary blood volume in both groups following albuterol. This resulted in an improvement in diffusion at the alveolar-capillary unit, and removal of the baseline difference in SpO2 by 90-minutes in CF subjects. These results demonstrate that EBC detects differences in ion regulation between healthy and CF individuals, and that albuterol mediates increases in Cl− in CF, suggesting that the benefits of albuterol extend beyond simple bronchodilation.

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Temperature Effects on Neuromuscular Transmission (Opener Muscle of Crayfish, Astacus Leptodactylus)

Journal of Experimental Biology ◽

10.1242/jeb.94.1.251 ◽

1981 ◽

Vol 94 (1) ◽

pp. 251-268

Author(s):

LUDWIG FISCHER ◽

ERNST FLOREY

Keyword(s):

Decay Time ◽

Neuromuscular Transmission ◽

Membrane Conductance ◽

Resting Potential ◽

Muscle Fibres ◽

Astacus Leptodactylus ◽

Excitation Contraction Coupling ◽

Contraction Coupling ◽

Temperature Range ◽

Parallel Change

In experiments on the opener muscle of the third walking legs of crayfish (Astacus leptodactylus) it was found that the mechanical tension developed in response to repetitive stimulation of the single motor axon increases over the entire temperature range from 30 down to 0°C. In contrast to this, the tension elicited by depolarizing single muscle fibres decreases with decreasing temperature; the threshold for excitation-contraction coupling is not significantly altered. With decreasing temperature the resting potential decreases (up to 2 mV/°C) but the amplitude and decay time of the e.p.s.p.'s increase. The time constant, λ, of e.p.s.p. decay has a Q10 of less than −2 in the range above 15 °C but reaches a value of −7 between 10 and 0°C. This pattern of temperature dependence is fully accounted for by a parallel change of membrane resistance and its reciprocal, the membrane conductance. The corresponding activation energies computed from λ-values approximate 3 kcal/mol at high temperature and 46 kcal/mol in the low temperature range. The combined effects of a lowered resting potential, an increased amplitude, and especially an increased decay time of e.p.s.p.s result in a drastic enhancement of the depolarization reached during summation of e.p.s.p.s as the temperature is decreased. These effects overcompensate the declining effectiveness of excitation-contraction coupling so that the entire process of neuromuscular transmission becomes more and more effective as the temperature declines. In order to reach the same tension lower frequencies of nerve stimulation are needed at lower temperatures.

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Slow ATP loss and the defense of ion homeostasis in the anoxic frog brain

Journal of Experimental Biology ◽

10.1242/jeb.204.20.3547 ◽

2001 ◽

Vol 204 (20) ◽

pp. 3547-3551

Author(s):

Debra L. Knickerbocker ◽

Peter L. Lutz

Keyword(s):

Initial Phase ◽

Ion Homeostasis ◽

Atp Depletion ◽

Neuronal Membrane ◽

Anoxia Tolerance ◽

Frog Brain ◽

Atp Levels ◽

Anoxic Depolarization ◽

Rate Of Increase ◽

The Brain

SUMMARY For most vertebrates, cutting off the oxygen supply to the brain results in a rapid (within minutes) loss of ATP, the failure of ATP-dependent ion-transport process, subsequent anoxic depolarization of neuronal membrane potential and consequential neuronal death. The few species that survive brain anoxia for days or months, such as the freshwater turtle Trachemys scripta, avoid anoxic depolarization and maintain brain ATP levels through a coordinated downregulation of brain energy demand processes. The frog Rana pipiens represents an intermediate in anoxia-tolerance, being able to survive brain anoxia for hours. However, the anoxic frog brain does not defend its energy stores. Instead, anoxia-tolerance appears to be related to a retarded rate of ATP depletion. To investigate the relationship between this slow ATP depletion and the loss of ionic homeostasis, cerebral extracellular K+ concentrations were monitored and ATP levels measured during anoxia, during the initial phase of anoxic depolarization and during complete anoxic depolarization. Extracellular K+ levels were maintained at normoxic levels for at least 3 h of anoxia, while ATP content decreased by 35 %. When ATP levels reached 0.33±0.06 mmol l–1 (mean ± s.e.m., N=5), extracellular K+ levels slowly started to increase. This value is thought to represent a critical ATP concentration for the maintenance of ion homeostasis. When extracellular [K+] reached an inflection value of 4.77±0.84 mmol l–1 (mean ± s.e.m., N=5), approximately 1 h later, the brain quickly depolarized. Part of the reduction in ATP demand was attributable to an approximately 50 % decrease in the rate of K+ efflux from the anoxic frog brain, which would also contribute to the retarded rate of increase in extracellular [K+] during the initial phase of anoxic depolarization. However, unlike the anoxia-tolerant turtle brain, adenosine did not appear to be involved in the downregulation of K+ leakage in the frog brain. The increased anoxia-tolerance of the frog brain is thought to be a matter more of slow death than of enhanced protective mechanisms.

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Dynamics and Consequences of Potassium Shifts in Skeletal Muscle and Heart During Exercise

Physiological Reviews ◽

10.1152/physrev.2000.80.4.1411 ◽

2000 ◽

Vol 80 (4) ◽

pp. 1411-1481 ◽

Cited By ~ 305

Author(s):

Ole M. Sejersted ◽

Gisela Sjøgaard

Keyword(s):

Skeletal Muscle ◽

Force Production ◽

Membrane Conductance ◽

Cell Swelling ◽

Modifying Factors ◽

Fast Twitch Muscle ◽

T Tubules ◽

Exercise Induced ◽

Fast Twitch ◽

Muscle Excitability

Since it became clear that K+shifts with exercise are extensive and can cause more than a doubling of the extracellular [K+] ([K+]s) as reviewed here, it has been suggested that these shifts may cause fatigue through the effect on muscle excitability and action potentials (AP). The cause of the K+shifts is a transient or long-lasting mismatch between outward repolarizing K+currents and K+influx carried by the Na+-K+pump. Several factors modify the effect of raised [K+]sduring exercise on membrane potential ( Em) and force production. 1) Membrane conductance to K+is variable and controlled by various K+channels. Low relative K+conductance will reduce the contribution of [K+]sto the Em. In addition, high Cl−conductance may stabilize the Emduring brief periods of large K+shifts. 2) The Na+-K+pump contributes with a hyperpolarizing current. 3) Cell swelling accompanies muscle contractions especially in fast-twitch muscle, although little in the heart. This will contribute considerably to the lowering of intracellular [K+] ([K+]c) and will attenuate the exercise-induced rise of intracellular [Na+] ([Na+]c). 4) The rise of [Na+]cis sufficient to activate the Na+-K+pump to completely compensate increased K+release in the heart, yet not in skeletal muscle. In skeletal muscle there is strong evidence for control of pump activity not only through hormones, but through a hitherto unidentified mechanism. 5) Ionic shifts within the skeletal muscle t tubules and in the heart in extracellular clefts may markedly affect excitation-contraction coupling. 6) Age and state of training together with nutritional state modify muscle K+content and the abundance of Na+-K+pumps. We conclude that despite modifying factors coming into play during muscle activity, the K+shifts with high-intensity exercise may contribute substantially to fatigue in skeletal muscle, whereas in the heart, except during ischemia, the K+balance is controlled much more effectively.

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Mechanisms of spreading depolarization in vertebrate and insect central nervous systems

Journal of Neurophysiology ◽

10.1152/jn.00352.2016 ◽

2016 ◽

Vol 116 (3) ◽

pp. 1117-1127 ◽

Cited By ~ 25

Author(s):

Kristin E. Spong ◽

R. David Andrew ◽

R. Meldrum Robertson

Keyword(s):

Locusta Migratoria ◽

Model Systems ◽

Control Mechanisms ◽

Cellular Mechanisms ◽

Nervous Systems ◽

Spreading Depolarization ◽

Metathoracic Ganglion ◽

Evolutionarily Conserved ◽

Central Nervous Systems ◽

The Central Nervous System

Spreading depolarization (SD) is generated in the central nervous systems of both vertebrates and invertebrates. SD manifests as a propagating wave of electrical depression caused by a massive redistribution of ions. Mammalian SD underlies a continuum of human pathologies from migraine to stroke damage, whereas insect SD is associated with environmental stress-induced neural shutdown. The general cellular mechanisms underlying SD seem to be evolutionarily conserved throughout the animal kingdom. In particular, SD in the central nervous system of Locusta migratoria and Drosophila melanogaster has all the hallmarks of mammalian SD. Locust SD is easily induced and monitored within the metathoracic ganglion (MTG) and can be modulated both pharmacologically and by preconditioning treatments. The finding that the fly brain supports repetitive waves of SD is relatively recent but noteworthy, since it provides a genetically tractable model system. Due to the human suffering caused by SD manifestations, elucidating control mechanisms that could ultimately attenuate brain susceptibility is essential. Here we review mechanisms of SD focusing on the similarities between mammalian and insect systems. Additionally we discuss advantages of using invertebrate model systems and propose insect SD as a valuable model for providing new insights to mammalian SD.

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Cell volume analysis of gramicidin-treated eccrine clear cells to study regulation of Cl channels

AJP Cell Physiology ◽

10.1152/ajpcell.1993.265.4.c1090 ◽

1993 ◽

Vol 265 (4) ◽

pp. C1090-C1099 ◽

Cited By ~ 7

Author(s):

M. Ohtsuyama ◽

Y. Suzuki ◽

G. Samman ◽

F. Sato ◽

K. Sato

Keyword(s):

Cell Volume ◽

Membrane Conductance ◽

Cell Swelling ◽

Tetraacetic Acid ◽

Sensitive Assay ◽

Current Clamp ◽

Volume Analysis ◽

Clear Cells ◽

Cyclic Monophosphate ◽

Cl Channels

Using voltage-current-clamp methods, we determined membrane potentials, relative ionic permeability, and membrane conductance of gramicidin (GC)-treated freshly dissociated eccrine clear cells. GC depolarized the membrane potential by 58 mV, increased the membrane conductance progressively over the time of exposure (mean of 1.7 times at 60 s and 4.6 times at 3 min), and increased the Na conductance of the membrane (from near 0 in control to 0.75 nS after GC). Image analysis coupled with GC treatment was then employed to study the regulation of Cl channels based on the premise that cell swelling was due to activation of Cl channels. Cell swelling was stimulated by methacholine (MCh, 3 microM) in the presence of GC. GC+MCh-induced cell swelling was inhibited by atropine, low extracellular Ca ([Ca]o < 1 nM), or removal of Cl. Thus MCh-induced cell swelling is most likely due to Ca-dependent activation of Cl channels. Isoproterenol (Iso), 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate, 3-isobutyl-1-methylxanthine, and forskolin also caused cell swelling in the presence of GC. Iso-induced cell swelling was abolished in a Cl-free medium and by diphenylamine-2-carboxylic acid, indicating that it is caused by adenosine 3',5'-cyclic monophosphate (cAMP)-mediated activation of Cl channels. Cl channels stimulated by MCh, but not those stimulated by Iso, were inhibited by preexposure to a low-Ca medium [nominally Ca free + 1 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, [Ca]o < 1 nM] for 20 s, suggesting that Ca-stimulated Cl channels are distinct from cAMP-dependent Cl channels. cAMP-stimulated Cl channels were, however, inhibited when the cells were exposed to the low-Ca medium for 60 s. The simple cell volume analysis of GC-treated cells is a sensitive assay system for both Ca- and cAMP-dependent Cl channels.(ABSTRACT TRUNCATED AT 250 WORDS)

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