Correlation Between Extracellular Focal Potentials and K+ Potentials Evoked by Primary Afferent Activity

1975 ◽  
Vol 53 (5) ◽  
pp. 912-922 ◽  
Author(s):  
K. Krnjević ◽  
M. E. Morris
Keyword(s):  
Time Course ◽  
Potassium Concentration ◽  
Extracellular Potassium ◽  
Cuneate Nucleus ◽  
Afferent Activity ◽  
Extracellular Potassium Concentration ◽  
Afferent Nerves ◽  
Focal Potentials ◽  
Constant Slope ◽  
Stimulation Of

There is a clear, positive correlation in amplitude between changes in potassium potentials (ΔEK) and focal potentials (ΔV) evoked by tetanic stimulation of afferent nerves in the cuneate nucleus and dorsal horn of cats under Dial anaesthesia or after decerebration. Data obtained with stimulations at various frequencies and intensities, or recording at different positions give a relatively constant slope of ΔV/ΔEK (varying between 0.2 and 0.6 in different experiments). These observations are fully consistent with the possibility that ΔV mainly reflects changes in extracellular potassium concentration caused by the release of K+ from active terminals. Differences in time course of ΔEK and ΔV evoked by single stimuli are a steep function of distance and therefore can be ascribed to the slowness of diffusion, without excluding the possibility of an early additional depolarizing effect by another mechanism.

Correlation of light-induced changes in retinal extracellular potassium concentration with c-wave of the electroretinogram

1976 ◽  
Vol 39 (5) ◽  
pp. 1117-1133 ◽  
Author(s):  
B. Oakley ◽  
D. G. Green
Keyword(s):  
Time Course ◽  
Potassium Concentration ◽  
Action Spectrum ◽  
Extracellular Potassium ◽  
Threshold Curve ◽  
Photoreceptor Layer ◽  
Extracellular Potassium Concentration ◽  
Increment Threshold ◽  
Induced Changes ◽  
Pigment Epithelial Cells

1. Double-barrel, potassium-specific microelectrodes have been used to measure light-induced transient changes in [K+]o in the frog eye cup preparation. These changes in [K+]o have been termed the potassioretinogram (KRG). 2. The KRG consists of two components: a rapid increase in [K+]o in the proximal retina and a slow decrease in [K+]o in the distal retina. 3. The KRG decrease has the rhodopsin action spectrum, is maximal in the photoreceptor layer, persists after aspartate treatment, and has an increment threshold curve which saturates at moderate background intensities. The rhodopsin rods are, therefore, most likely the only neurons which generate this ionic change, although the Muller (glial) cells may also be involved in this process. 4. The KRG decrease has the same time course as the c-wave of the electroretinogram for all variations in the stimulus parameters, including intensity, duration, and chromaticity. 5. It is suggested that the c-wave may be produced by the pigment epithelial cells as they hyperpolarize in response to the decrease in [K+]o around the photoreceptors.

Insulin stimulation of an electrogenic pump at high extracellular potassium concentration

1985 ◽  
Vol 249 (1) ◽  
pp. E12-E16
Author(s):  
F. S. Wu ◽  
K. Zierler
Keyword(s):  
Skeletal Muscle ◽  
Potassium Concentration ◽  
Equilibrium Potential ◽  
Extracellular Potassium ◽  
Insulin Stimulation ◽  
Rat Skeletal Muscle ◽  
Extracellular Potassium Concentration ◽  
High K ◽  
Na Ions ◽  
Stimulation Of

There is no agreement about the immediate mechanism by which insulin hyperpolarizes skeletal muscle, adipocytes, and myocardium. Of three candidates, one has been eliminated; the hyperpolarization is not secondary to an increase in intracellular [K]. There are reports that insulin hyperpolarizes by increasing relative permeability to K compared with that to Na ions, and other reports that insulin stimulates an ouabain-sensitive electrogenic Na-K exchange pump. Our evidence has been interpreted to support the former and deny the latter, when rat skeletal muscle is bathed at normal [K]. Crucial evidence for the latter has not been reported: insulin hyperpolarizes to a potential more negative than the K equilibrium potential. We now report that when rat caudofemoralis muscle is incubated with insulin at normal extracellular [K], then depolarized by increasing extracellular [K] to 38.4 mM, by equimolar substitution of KCl for NaCl, there is hyperpolarization compared with potentials of muscles treated similarly with respect to [K] but without insulin. Under these circumstances, the membrane potential in the presence of insulin is more negative than the new K equilibrium potential, and, in contrast to our previous experience with muscles bathed only in normal [K], the hyperpolarization in high [K] is reduced or eliminated by ouabain.

Effects of dantrolene and D2O on K+-stimulated respiration of skeletal muscle

1982 ◽  
Vol 243 (1) ◽  
pp. C87-C95 ◽  
Author(s):  
D. Erlij ◽  
W. K. Shen ◽  
P. Reinach ◽  
H. Schoen
Keyword(s):  
Skeletal Muscle ◽  
Potassium Concentration ◽  
Extracellular Potassium ◽  
Frog Skeletal Muscle ◽  
Extracellular Potassium Concentration ◽  
Na Efflux ◽  
High Level ◽  
The Relationship ◽  
Peak Increase ◽  
Stimulation Of

We have examined the effects of dantrolene and D2O on the K+-stimulated respiration in frog skeletal muscle. The threshold for K+ stimulation was around 10 mM extracellular potassium concentration ([K+]o). A further marked increase in respiration to levels about ten times the resting level was noted when [K+]o was between 15 and 20 mM. The increase was sustained for hours when [K+]o was less than 20 mM; however, with higher concentrations the stimulation consisted of an initial burst followed by a decline. Dantrolene shifted the relationship between [K+]o and peak increase in respiration toward higher [K+]o by about 10 mM; in addition it nearly completely blocked the sustained component of the increase. D2O, nearly abolished the K+-induced respiration. Neither agent shifted the relationship between [K+]o and membrane potential nor abolished the stimulation of respiration caused by caffeine. Dantrolene did not block the stimulation of Na+ efflux caused by 15 mM K+. The results with these agents are consistent with the proposal that K+-stimulated respiration is due to Ca2+ release into the cytoplasm. In addition, they provide evidence that the stimulated rate of Ca2+ release into the cytoplasm can remain at a persistently high level for hours provided [K+]o does not exceed 20 mM. We calculated that the level of this constant Ca2+ release is about 3.4 X 10(16) ions/(s.cm3).

scholarly journals Junctional resistance and action potential delay between embryonic heart cell aggregates.

1980 ◽  
Vol 75 (6) ◽  
pp. 633-654 ◽  
Author(s):  
D E Clapham ◽  
A Shrier ◽  
R L DeHaan
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Time Course ◽  
Potassium Concentration ◽  
Aggregate Size ◽  
Heart Cell ◽  
Extracellular Potassium ◽  
Cell Aggregates ◽  
Extracellular Potassium Concentration ◽  
Junctional Resistance

Spheroidal aggregates of embryonic chick ventricle cells were brought into contact and allowed to synchronize their spontaneous beats. Action potentials were recorded with both intracellular and extracellular electrodes. The degree of electrical interaction between the newly apposed aggregates was assessed by measuring the delay or latency (L) between the entrained action potentials, and by determining directly interaggregate coupling resistance (Rc) with injected current pulses. Aggregate size, contact area between the aggregates, and extracellular potassium concentration (Ko+) were important variables regulating the time-course of coupling. When these variables were controlled, L and Rc were found to be linearly related after beat synchrony was achieved. In 4.8 mM Ko+ L/Rc = 3.7 ms/M omega; in 1.3 mM Ko+ L/Rc = 10.1 ms/M omega. We conclude that action potential delay between heart cell aggregates can be related quantitatively to Rc.

Brain extracellular potassium and genera anaesthetics

1978 ◽  
Vol 56 (5) ◽  
pp. 863-872 ◽  
Author(s):  
M. E. Morris
Keyword(s):  
Peripheral Nerves ◽  
Low Frequency ◽  
Extracellular Potassium ◽  
General Anaesthetic ◽  
Cuneate Nucleus ◽  
Anaesthetic Agents ◽  
Severe Hypotension ◽  
Focal Potentials ◽  
Small Voltage ◽  
Stimulation Of

General anaesthetic agents (halothane, trichlorethylene, methohexital, pentobarbital, and alphaxalone–alphadolone) depress the extracellular accumulations (ΔEk) and associated focal potentials (ΔV) which are evoked in the cuneate nucleus by tetanic stimulation of peripheral nerves. Depressions of ΔV are significantly greater than those of ΔEk; at the same time there is a dissociation of the relation between ΔV and ΔEk. There are no detectable changes in the resting levels of K+ or the small voltage shifts evoked by low-frequency intranuclear stimulation with a microelectrode. When anaesthesia produces severe hypotension, augmentations of [K+]0 occur which can be attributed to depression of electrogenic Na–K pumping. A possible explanation of the reduction in K+ release resulting from afferent fibre activity would be failure of conduction caused by membrane stabilization or hyperpolarization.

scholarly journals Effects of the rod receptor potential upon retinal extracellular potassium concentration.

1979 ◽  
Vol 74 (6) ◽  
pp. 713-737 ◽  
Author(s):  
B Oakley ◽  
D G Flaming ◽  
K T Brown
Keyword(s):  
Time Course ◽  
Potassium Concentration ◽  
Receptor Potential ◽  
Ion Concentration ◽  
Extracellular Potassium ◽  
Photoreceptor Layer ◽  
Extracellular Potassium Concentration ◽  
Wide Range ◽  
The Relationship ◽  
Toad Bufo

It has been hypothesized that the light-evoked rod hyperpolarization (the receptor potential) initiates the light-evoked decrease in extracellular potassium ion concentration, [K+]o, in the distal retina. The hypothesis was tested using the isolated, superfused retina of the toad, Bufo marinus; the receptor potential was recorded intracellularly from red rods, and [K+]o was measured in the photoreceptor layer with K+-specific microelectrodes. In support of the hypothesis, variations in stimulus irradiance or duration, or in retinal temperature, produced qualitatively similar effects on both the receptor potential and the decrease in [K+]o. A mechanism for the relationship between the receptor potential and the decrease in [K+]o was suggested by Matsuura et al. (1978. Vision Res. 18:767-775). In the dark, the passive efflux of K+ out of the rod is balanced by an equal influx of K+ fromthe Na+/K+ pump. The light-evoked rod hyperpolarization is assumed to reduce the passive efflux, with little effect on the pump. Thus, the influx will exceed the efflux, and [K+]o will decrease. Consistent with this mechanism, the largest and most rapid decrease in [K+]o was measured adjacent to the rod inner segments, where the Na+/K+ pump is most likely located; in addition, inhibition of the pump with ouabain abolished the decrease in [K]o more rapidly than the rod hyperpolarization. Based upon this mechanism, Matsuura et al. (1978) developed a mathematical model: over a wide range of stimulus irradiance, this model successfully predicts the time-course of the decrease in [K+]o, given only the time-course of the rod hyperpolarization.

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