scholarly journals The effects of altering extracellular potassium ion concentration on the membrane potential and circadian clock of Paramecium bursaria.

1994 ◽  
Vol 197 (1) ◽  
pp. 295-308
Author(s):  
C H Johnson ◽  
Y Nakaoka ◽  
I Miwa
Keyword(s):  
Membrane Potential ◽  
Circadian Clock ◽  
Biological Clock ◽  
Cellular Level ◽  
Ion Concentration ◽  
Extracellular Potassium ◽  
Extracellular Potassium Concentration ◽  
Transmembrane Flux ◽  
Circadian Organization ◽  
The Impact

In some neural models of circadian rhythmicity, membrane potential and transmembrane flux of potassium and calcium ions appear to play important roles in the entrainment and central mechanisms of the biological clock. We wondered whether these cellular variables might be generally involved in circadian clocks, even non-neural clocks. Therefore, we tested the impact of changing extracellular potassium level on the circadian rhythm of photoaccumulation of Paramecium cells, whose membrane potential responds to changes of extracellular potassium in a manner similar to that of neurones. We found that pulse or step changes of extracellular potassium concentration did not phase-shift the circadian clock of P. bursaria cells in a phase-specific manner. Furthermore, modifying the extracellular concentration of calcium did not affect the magnitude of light-induced phase resetting. Therefore, while membrane potential and calcium fluxes may be crucial components of the circadian clock system in some organisms, especially in neural systems that involve intercellular communication, the P. bursaria data indicate that membrane potential changes are not necessarily an intrinsic component of circadian organization at the cellular level.

Effect of elevated potassium on the ion content of mouse astrocytes and neurons

1992 ◽  
Vol 70 (S1) ◽  
pp. S263-S268 ◽  
Author(s):  
H. Steve White ◽  
Sien Yao Chow ◽  
Y. C. Yen-Chow ◽  
Dixon M. Woodbury
Keyword(s):  
Cortical Neurons ◽  
Cell Types ◽  
Mouse Cell ◽  
Ion Concentration ◽  
Cellular Heterogeneity ◽  
Resting Membrane Potential ◽  
Extracellular Potassium ◽  
Individual Response ◽  
Extracellular Potassium Concentration ◽  
The Brain

Potassium is tightly regulated within the extracellular compartment of the brain. Nonetheless, it can increase 3- to 4-fold during periods of intense seizure activity and 10- to 20-fold under certain pathological conditions such as spreading depression. Within the central nervous system, neurons and astrocytes are both affected by shifts in the extracellular concentration of potassium. Elevated potassium can lead to a redistribution of other ions (e.g., calcium, sodium, chloride, hydrogen, etc.) within the cellular compartment of the brain. Small shifts in the extracellular potassium concentration can markedly affect acid–base homeostasis, energy metabolism, and volume regulation of these two brain cells. Since normal neuronal function is tightly coupled to the ability of the surrounding glial cells to regulate ionic shifts within the brain and since both cell types can be affected by shifts in the extracellular potassium, it is important to characterize their individual response to an elevation of this ion. This review describes the results of side-by-side studies conducted on cortical neurons and astrocytes, which assessed the effect of elevated potassium on their resting membrane potential, intracellular volume, and their intracellular concentration of potassium, sodium, and chloride. The results obtained from these studies suggest that there exists a marked cellular heterogeneity between neurons and astrocytes in their response to an elevation in the extracellular potassium concentration.Key words: astrocytes, neurons, ion concentration, neuronal–glial interactions, mouse, cell culture.

scholarly journals In Vivo Neocortical [K]o Modulation by Targeted Stimulation of Astrocytes

2021 ◽  
Vol 22 (16) ◽  
pp. 8658
Author(s):  
Azin EbrahimAmini ◽  
Shanthini Mylvaganam ◽  
Paolo Bazzigaluppi ◽  
Mohamad Khazaei ◽  
Alexander Velumian ◽  
...  
Keyword(s):  
Nervous System ◽  
Membrane Potential ◽  
Potassium Ion ◽  
Ion Concentration ◽  
Extracellular Potassium ◽  
Spreading Depolarization ◽  
Potential Tool ◽  
Stimulation Of

A normally functioning nervous system requires normal extracellular potassium ion concentration ([K]o). Throughout the nervous system, several processes, including those of an astrocytic nature, are involved in [K]o regulation. In this study we investigated the effect of astrocytic photostimulation on [K]o. We hypothesized that in vivo photostimulation of eNpHR-expressing astrocytes leads to a decreased [K]o. Using optogenetic and electrophysiological techniques we showed that stimulation of eNpHR-expressing astrocytes resulted in a significantly decreased resting [K]o and evoked K responses. The amplitude of the concomitant spreading depolarization-like events also decreased. Our results imply that astrocytic membrane potential modification could be a potential tool for adjusting the [K]o.

Disorders of potassium homeostasis

2010 ◽  
pp. 3831-3845 ◽  
Author(s):  
J Firth
Keyword(s):  
Membrane Potential ◽  
Potassium Concentration ◽  
Resting Membrane Potential ◽  
Extracellular Potassium ◽  
Normal Range ◽  
Critical Determinant ◽  
Potassium Homeostasis ◽  
Extracellular Potassium Concentration

The normal range of potassium concentration in serum is 3.5 to 5.0 mmol/litre and within cells it is 150 to 160 mmol/litre, the ratio of intracellular to extracellular potassium concentration being a critical determinant of cellular resting membrane potential and thereby of the function of excitable tissues....

scholarly journals Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness

2014 ◽  
Vol 112 (4) ◽  
pp. 1232-1237 ◽  
Author(s):  
Anne-Marie Chang ◽  
Daniel Aeschbach ◽  
Jeanne F. Duffy ◽  
Charles A. Czeisler
Keyword(s):  
Circadian Clock ◽  
Technology Use ◽  
Negative Impact ◽  
Light Exposure ◽  
Biological Effects ◽  
Biological Clock ◽  
Health And Safety ◽  
Light Emitting ◽  
Circadian Phase ◽  
The Impact

In the past 50 y, there has been a decline in average sleep duration and quality, with adverse consequences on general health. A representative survey of 1,508 American adults recently revealed that 90% of Americans used some type of electronics at least a few nights per week within 1 h before bedtime. Mounting evidence from countries around the world shows the negative impact of such technology use on sleep. This negative impact on sleep may be due to the short-wavelength–enriched light emitted by these electronic devices, given that artificial-light exposure has been shown experimentally to produce alerting effects, suppress melatonin, and phase-shift the biological clock. A few reports have shown that these devices suppress melatonin levels, but little is known about the effects on circadian phase or the following sleep episode, exposing a substantial gap in our knowledge of how this increasingly popular technology affects sleep. Here we compare the biological effects of reading an electronic book on a light-emitting device (LE-eBook) with reading a printed book in the hours before bedtime. Participants reading an LE-eBook took longer to fall asleep and had reduced evening sleepiness, reduced melatonin secretion, later timing of their circadian clock, and reduced next-morning alertness than when reading a printed book. These results demonstrate that evening exposure to an LE-eBook phase-delays the circadian clock, acutely suppresses melatonin, and has important implications for understanding the impact of such technologies on sleep, performance, health, and safety.

Sensory neurons in leech central nervous system: changes in potassium conductance an excitation threshold

1976 ◽  
Vol 39 (6) ◽  
pp. 1184-1192 ◽  
Author(s):  
W. R. Schlue
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Membrane Potential ◽  
Action Potential ◽  
Sensory Neurons ◽  
Potassium Concentration ◽  
Potassium Conductance ◽  
Extracellular Potassium ◽  
Extracellular Potassium Concentration ◽  
Accommodation Coefficients

1. The sensory neurons in the leech central nervous system differ in their accommodation to linearly rising currents. Advantage was taken of these differences to study the ionic mechanism of accommodation in single pairs of N (noxious), P (pressure), and T (touch) cells. 2. Nonlinearities in membrane-potential changes and current-voltage relationships with square-wave and ramp currents are more pronounced in P and T cells than in N cells. The accommodation coefficients increase in conditions that reflect this delayed rectification. When rectification is absent, the accommodation coefficients depart from unity only slightly or not at all. 3. Accommodation coefficients remain unchanged when half of the chloride in the bathing medium is replaced by sulfate. Accommodation coefficients become greater when the extracellular potassium concentration is reduced from 4 to 0 mM, and decrease when the concentration is raised to 8 mM. The membrane potential changes by only a few millivolts. 4. As extracellular potassium concentration is increased, the action potential is lengthened and the maximal rate of fall of the action potential is reduced. With concentrations greater than 4 mM these relationships are linear, but depart from linearity at lower concentrations. The amplitude of the undershoot decreases linearly as the extracellular potassium concentration increases from 4 to 16 mM, and increases non-linearly at concentrations below 4 mM. 5. The rapid accommodation of leech neurons is based primarily on an increased potassium conductance. The possibility is considered that concentration changes like those produced experimentally may occur naturally, affecting integrative processes in the central nervous system.

scholarly journals Membrane Potential of Brown Adipose Tissue

1968 ◽  
Vol 52 (6) ◽  
pp. 925-940 ◽  
Author(s):  
L. Girardier ◽  
J. Seydoux ◽  
T. Clausen
Keyword(s):  
Adipose Tissue ◽  
Membrane Potential ◽  
Brown Adipose Tissue ◽  
Membrane Resistance ◽  
Mean Value ◽  
Extracellular Potassium ◽  
Bicarbonate Buffer ◽  
Interscapular Brown Adipose Tissue ◽  
Extracellular Potassium Concentration ◽  
Brown Adipose

Membrane potentials were recorded in isolated segments of interscapular brown adipose tissue from rats. After equilibration at 29°C in Krebs-Ringer bicarbonate buffer a mean value of -51 ± 4 mv (SD) was found. This level could be maintained for up to 5 hr. The mean effective membrane resistance was 1.35 ± 0.45 megohm. The membrane potential was a function of the extracellular potassium concentration. Ouabain (10-6-10-3 M) and incubation in K-free buffer produced progressive depolarization. Epinephrine and norepinephrine in concentrations as low as 10-8 g/ml produced a prompt depolarization. Cooling of the tissue and lowering of the oxygen tension caused a marked and reversible decrease in the membrane potential. In tissue obtained from cold-adapted rats, the membrane potential was considerably diminished. 6Assuming that the membrane potential is some function of the Na permeability of the plasma membrane it is suggested that an increase in the rate of active Na-K transport and ensuing ADP formation might contribute to the increase in respiration seen during exposure to thermogenic stimuli.

scholarly journals The membrane potential of human platelets

Blood ◽  
1983 ◽  
Vol 61 (1) ◽  
pp. 180-185
Author(s):  
LT Friedhoff ◽  
M Sonenberg
Keyword(s):  
Membrane Potential ◽  
Calcium Ion ◽  
Human Platelet ◽  
Adenosine Diphosphate ◽  
Human Platelets ◽  
Ion Concentration ◽  
Extracellular Potassium ◽  
Ion Concentrations ◽  
Calcium Ion Concentration ◽  
Extracellular Sodium

The membrane potential of the human platelet was investigated using the membrane potential probes 3,3′-dipropyl-2,2′-thiadicarbocyanine iodide and tritiated triphenylmethylphosphonium bromide. The membrane potential in physiologic buffer was estimated to be 52–60 mV inside negative. The membrane was depolarized when extracellular potassium or hydrogen ion concentrations were increased. Changes in extracellular sodium, chloride, or calcium ion concentration had no measurable effect on membrane potential. Elevated extracellular potassium has been shown to increase platelet sensitivity to the aggregating agent, adenosine diphosphate. Our results show that changes in extracellular ion concentrations that depolarize platelets increase platelet sensitivity to aggregating agents. These results suggest that membrane potential changes may play a role in modulating the response of platelets to aggregating agents.

scholarly journals The membrane potential of human platelets

Blood ◽  
1983 ◽  
Vol 61 (1) ◽  
pp. 180-185 ◽  
Author(s):  
LT Friedhoff ◽  
M Sonenberg
Keyword(s):  
Membrane Potential ◽  
Calcium Ion ◽  
Human Platelet ◽  
Adenosine Diphosphate ◽  
Human Platelets ◽  
Ion Concentration ◽  
Extracellular Potassium ◽  
Ion Concentrations ◽  
Calcium Ion Concentration ◽  
Extracellular Sodium

Abstract The membrane potential of the human platelet was investigated using the membrane potential probes 3,3′-dipropyl-2,2′-thiadicarbocyanine iodide and tritiated triphenylmethylphosphonium bromide. The membrane potential in physiologic buffer was estimated to be 52–60 mV inside negative. The membrane was depolarized when extracellular potassium or hydrogen ion concentrations were increased. Changes in extracellular sodium, chloride, or calcium ion concentration had no measurable effect on membrane potential. Elevated extracellular potassium has been shown to increase platelet sensitivity to the aggregating agent, adenosine diphosphate. Our results show that changes in extracellular ion concentrations that depolarize platelets increase platelet sensitivity to aggregating agents. These results suggest that membrane potential changes may play a role in modulating the response of platelets to aggregating agents.

Alkaline and acid transients in cerebellar microenvironment

1983 ◽  
Vol 49 (3) ◽  
pp. 831-850 ◽  
Author(s):  
R. P. Kraig ◽  
C. R. Ferreira-Filho ◽  
C. Nicholson
Keyword(s):  
Neuronal Activity ◽  
Cerebellar Cortex ◽  
Stimulus Frequency ◽  
Ringer Solution ◽  
Weak Acid ◽  
Ion Concentration ◽  
Extracellular Potassium ◽  
Base Line ◽  
Extracellular Potassium Concentration ◽  
The Brain

1. Extracellular pH (pHo) was measured in the cerebellar cortex of the rat using a recently developed liquid membrane ion-selective micropipette (ISM). pHo was determined during stimulus-evoked neuronal activity, elevated extracellular potassium concentration, [K+]o, spreading depression (SD), and complete ischemia. In many experiments [K+]o was simultaneously determined. 2. A train of local surface stimuli (LOC) produced an initial alkaline shift in pHo from a base line of 7.20-7.30 to 7.25-7.35. This was followed by a long-lasting acid phase that reached a plateau of 7.05-7.15 after 64 s of stimulation. pHo decrease was related to stimulus frequency, intensity, and duration. 3. Superfusion with Ringer solution containing manganese ions rapidly abolished parallel fiber-induced Purkinje cell synaptic depolarization together with the alkaline shifts while enhancing the acid shifts. 4. Superfusion of the cerebellar cortex with Ringer solution containing increasingly elevated [K+] progressively lowered pHo to a plateau of 6.95-7.05. The acidification occurred in the presence of ouabain but was reversed on return to the normal [K+]o or with the addition of the glycolytic blocker, fluoride. Stimulus-evoked alkaline shifts were enhanced by K+-Ringer superfusion. These experiments suggested that the acid shift was due to the metabolic production of an anion, possibly lactate. 5. Elevation of [K+]o above 8-12 mM often produced oscillation in pHo and [K+]o with a period of about 40 s. Sometimes these oscillations ended in a spontaneous SD or SD could be evoked by stimulation. Under these conditions of raised [K+]o, the SD consisted of a very pronounced alkaline transient followed by a small, long-lasting acid shift. When SD was induced by conditioning the cerebellum with proprionate or lowered NaCl, the alkaline phase was reduced and the acid enhanced. 6. Complete ischemia began with a progressive decrease of pHo and rise in [K+]o. When [K+]o reached 12 mM, a second more rapid rise in [K+]o to 40 mM or more occurred. This was correlated with 0.1-0.2 pHo transient increase similar to that seen during SD. pHo eventually reached a plateau of 6.60-6.80, close to neutrality. 7. Superfusion with Ringer solution containing acetazolamide immediately altered pHo homeostasis by increasing base-line pHo by about 0.10 and enhanced the induced pHo changes. These results suggest that carbonic anhydrase (CA) is important for acute buffering of the brain extracellular microenvironment. 8. The above results were interpreted in terms of changes in extracellular strong ion concentration differences ( [SID]o), extracellular concentration of total weak acid ( [Atot]o) and partial pressure of CO2 (Pco2) in the brain microenvironment. The results indicate that neuronal activity produces changes in many of the constituents of the microenvironment.

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