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PubMed1978

Membrane potential of spinal motoneurons during natural sleep in cats.

The membrane potential of spinal motoneurons was recorded during wakefulness, NREM sleep, and REM sleep in minimally restrained, behaving cats. At the onset of sleep, the membrane potential generally increased in polarization in rough proportion to time spent asleep. During the postural atonia of REM sleep, the membrane potential of all motoneurons was tonically hyperpolarized. Antecedents of NREM sleep electromyographic suppressions, and REM sleep myoclonic twitches were seen as transient hyperpolarizations and depolarizations, respectively.

Animals↗
PubMedDate not supplied

Mitochondrial membrane potential in aging cells.

Decreased mitochondrial membrane potential (DeltaPsi(M)) has been found in a variety of aging cell types from several mammalian species. The physiological significance and mechanisms of the decreased DeltaPsi(M) in aging are not well understood. This review considers the generation of DeltaPsi(M) and its role in ATP generation together with factors that modify DeltaPsi(M) with emphasis on mitochondrial membrane permeability, particularly the role of a multiprotein membrane megapore, the mitochondrial permeability transition pore complex (PTPC). Previous data showing decreased DeltaPsi(M) in aged cells is considered in relation to the methods available to estimate DeltaPsi(M). In the past the majority of studies used whole cell rhodamine 123 fluorescence to estimate DeltaPsi(M) in lymphocytes from mice or rats. Imaging of DeltaPsi(M) in living, in situ mitochondria using laser confocal scanning microscopy offers advantages over whole cell measurements or those from isolated mitochondria, particularly if several different potentiometric dyes are employed. Furthermore, high resolution imaging of the newer fixable potentiometric dyes allows immunocytochemistry for specific proteins and DeltaPsi(M) to be examined in the same cells or even the same mitochondria. We found that decreased DeltaPsi(M) in p53 overexpression-induced or naturally occurring senescence is associated with decreased responsiveness of the PTPC to agents that induce either its opening or closing. The decreased PTPC responsiveness seems to reflect, at least in part, decreased levels of a key PTPC protein, the adenine nucleotide translocase. We also consider the possible basis for decreased DeltaPsi(M) in fibroblasts from patients with Parkinson's disease, an age-related neurodegenerative disease. Finally, we speculate on the mechanisms and functional significance of decreased DeltaPsi(M) in aging.

Aging↗
PubMed2000

Membrane potential and firing rate in cat primary visual cortex.

We have investigated the relationship between membrane potential and firing rate in cat visual cortex and found that the spike threshold contributes substantially to the sharpness of orientation tuning. The half-width at half-height of the tuning of the spike responses was 23 +/- 8 degrees, compared with 38 +/- 15 degrees for the membrane potential responses. Direction selectivity was also greater in spike responses (direction index, 0.61 +/- 0.35) than in membrane potential responses (0.28 +/- 0.21). Threshold also increased the distinction between simple and complex cells, which is commonly based on the linearity of the spike responses to drifting sinusoidal gratings. In many simple cells, such stimuli evoked substantial elevations in the mean potential, which are nonlinear. Being subthreshold, these elevations would be hard to detect in the firing rate responses. Moreover, just as simple cells displayed various degrees of nonlinearity, complex cells displayed various degrees of linearity. We fitted the firing rates with a classic rectification model in which firing rate is zero at potentials below a threshold and grows linearly with the potential above threshold. When the model was applied to a low-pass-filtered version of the membrane potential (with spikes removed), the estimated values of threshold (-54.4 +/- 1.4 mV) and linear gain (7.2 +/- 0.6 spikes. sec(-1). mV(-1)) were similar across the population. The predicted firing rates matched the observed firing rates well and accounted for the sharpening of orientation tuning of the spike responses relative to that of the membrane potential. As it was for stimulus orientation, threshold was also independent of stimulus contrast. The rectification model accounted for the dependence of spike responses on contrast and, because of a stimulus-induced tonic hyperpolarization, for the response adaptation induced by prolonged stimulation. Because gain and threshold are unaffected by visual stimulation and by adaptation, we suggest that they are constant under all conditions.

Action Potentials↗
PubMed1988

The stoichiometry of charge translocation by cytochrome oxidase and the cytochrome bc1 complex of mitochondria at high membrane potential.

The q+/2e stoichiometries (number of charges translocated per electron pair transferred) of cytochrome oxidase and the cytochrome bc1 complex in rat liver mitochondria were determined at a range of membrane potentials up to 180 mV. The method used was similar to the one used in the preceding paper by us in this journal to determine the q+/O stoichiometry of the mitochondrial electron transport chain from succinate to oxygen. The measured q+/2e stoichiometry of cytochrome oxidase was 3.5 positive charges per O atom reduced at low membrane potential (120 mV) and it decreased to about 1.5 at high membrane potential (180 mV). The measured q+/2e stoichiometry of the cytochrome bc1 complex was between 1 and 1.25 positive charges ejected per electron pair and did not change significantly as delta psi was varied from 85 mV to 157 mV. The sum of the q+/2e stoichiometries of cytochrome oxidase and the cytochrome bc1 complex determined separately was similar to their value determined together for electron transport from succinate to oxygen over the range of membrane potentials studied. The most probable interpretation of these results is that the stoichiometry of the cytochrome bc1 complex is invariant over a range of membrane potentials and that the q+/2e stoichiometry of cytochrome oxidase decreases from 4 at low membrane potential to 2 at high membrane potential.

Animals↗
PubMed1984

Effect of glucose and pyruvate metabolism on membrane potential in synaptosomes.

Fluorescence changes of rhodamine 6G in synaptosomal suspension, which are correlated to changes in membrane potential in synaptosomes, were measured in the presence of various monosaccharides and organic acids. Addition of D-glucose, D-mannose, pyruvate and L-lactate hyperpolarized the membrane potential, whereas D-fructose, L-glucose, D-galactose, citrate, succinate and L-glutamate were without effect on the membrane potential. Hyperpolarization induced by D-glucose was inhibited by cytochalasin B, phloretin, iodoacetate, F- and 2-deoxy-D-glucose, but not inhibited by oligomycin or phlorizin. On the other hand, hyperpolarization induced by pyruvate was inhibited by alpha-cyanocinnamate or phloretin, but not inhibited by cytochalasin B or F-. Elimination of Na+ in physiological saline depressed hyperpolarization of membrane potential induced by addition of D-glucose, L-lactate or pyruvate. These results suggest that the activity of (Na+ + K+)-ATPase in plasma membranes of synaptosomes is increased by ATP formed by glycolysis, and that the accumulated K+ in synaptosomes hyperpolarizes the membrane potential.

Animals↗
PubMed1996

Direct influence of the sodium pump on the membrane potential of vomeronasal chemoreceptor neurones in frog.

1. Whole-cell measurements were made from microvillous receptor neurones isolated from the frog vomeronasal organ. We examined the mechanisms that determined the value of the resting membrane potential. 2. Cells recorded in Ringer solution containing 4 mM K+ showed a resting membrane potential of -88 +/- 20 mV (mean +/- 1 S.D., n = 56). Sixty-six per cent of the cells had stable resting potentials more negative than the calculated equilibrium potentials for K+ (EK, -82 mV) indicating the presence of a hyperpolarizing outward pump current. 3. Cells recorded with an intracellular solution containing Na+ instead of K+, to set EK at 0 mV, presented stable membrane potentials in the range -65 to -119 mV when bathed in a normal Ringer solution. 4. Ouabain, a specific inhibitor of the Na+,K(+)-ATPase, blocked the outward sodium pump current (Ip) and depolarized the membrane. 5. The sodium pump current, measured as the current blocked by 0.5 mM dihydro-ouabain, was linearly related to the membrane potential in the range -60 to -120 mV. The reversal potential measured with a calculated free energy of ATP hydrolysis of -36.2 kJ mol-1 was estimated to be -143 mV. 6. Reduction of the external K+ concentration to 0 mM depolarized the membrane to less than -40 mV. Voltage-clamp observations in this condition indicated a reduction of Ip. Ouabain added to the bath reduced the blocking effect of low external K+. The addition of external K+ activated Ip and induced a rapid hyperpolarization of the cell membrane. 7. At membrane potentials more negative than -80 mV, an inward rectifying depolarizing current characterized as Ih was activated. When Ih was blocked by 5 mM external Cs+ the resting membrane potential increased. 8. These data indicate that the membrane potential of the vomeronasal receptor neurones is not generated by a passive diffusion of K+ ions but by the hyperpolarizing current created by the Na+,K(+)-ATPase. We propose that the resting potential is set by a balance between Ip and Ih. The physiological implications of these mechanisms for setting the resting potential are discussed.

Animals↗
PubMed2006

Evaluating the validity of blood-based membrane potential changes for the identification of bipolar disorder I.

OBJECTIVE: The objective of this study was to develop a diagnostic blood test for bipolar disorder I using membrane potentials as biological markers. METHODS: We measured the fluorescence intensity of a dye sensitive to membrane potential in whole blood samples from bipolar I, unipolar, schizophrenic patients, and psychiatrically normal controls. Patients were diagnosed through structured clinical interviews according to DSM-IV. Both the t-test and logistic regression analysis were used to analyze the data. RESULTS: The membrane potential as indicated by the fluorescence intensity of the membrane potential dye in blood cells drawn from patients with bipolar disorder I was significantly different from the blood cells drawn from unipolar and schizophrenic patients, and from psychiatrically normal controls (P<0.001). The specificity and sensitivity were determined to be 0.88 and 0.78 respectively which compared well with the state of the art diagnostic techniques for other diseases. Logistic regression analysis revealed that the membrane potential was a reliable predictor which could be used as a diagnostic marker for bipolar I. CONCLUSIONS: These results indicate that the membrane potential of blood cells can be used as a diagnostic marker to augment the DSM-IV diagnosis of bipolar disorder I. Expanded clinical trials are needed to establish this technique for general use.

Adult↗
PubMed1968

Statistical analysis of membrane potential fluctuations. Relation with presynaptic spike train.

In a study of integration at the single neuron level, the relationships between the postsynaptic membrane potential and the presynaptic spike train were analyzed. Fluctuations in membrane potential of neurons in the visceral ganglion of Aplysia were measured and described by histograms. The histogram estimates the probability density function of the membrane potential. Comparisons were made among histograms when there was no synaptic input, and when there was a single input in which variations were made in the PSP (postsynaptic potential) sign, i.e. excitatory or inhibitory, and arrival statistics, e.g. slow or fast, regular, Poisson-like, or patterned. This was examined in cells where the membrane potential was constant and in cells in which there was spontaneous pacemaker activity. The form of the histogram depended on whether the neuron was spontaneously quiescent or a pacemaker, or whether it received presynaptic input and, if it did, on the sign and temporal characteristics of such input. From such histograms the mean firing rate of output spike trains can be predicted; additional information of a temporal nature is required, however, to predict features of the interval structure of the output train. Suggestions are made concerning the way the nervous system might utilize the information summarized in the membrane potential histogram.

Evoked Potentials↗
PubMed1991

Effects of vasoactive agonists on the membrane potential of cultured bovine aortic and guinea-pig coronary endothelium.

1. The effects of bradykinin, ATP, adenosine, histamine and thrombin on the membrane potential of confluent monolayers of cultured bovine aortic endothelial cells (BAECs) and guinea-pig coronary endothelial cells (GCECs) were studied at 37 degrees C using the whole-cell mode of the patch-clamp technique. 2. The amplitude histogram of the resting potentials of BAEC monolayers showed a bimodal distribution with one peak around -25 mV and another peak around -85 mV. Transitions from one potential level to the other were observed. The bistable membrane potential can be explained by an N-shaped current-voltage relation of the endothelial cell membrane. 3. When BAECs with a low resting potential (-10 to -30 mV) were superfused with maximally effective concentrations of ATP (2-10 microM) an initial hyperpolarization of -80 to -90 mV was observed which decayed to a plateau of about -60 mV within 1 min. When ATP was removed after 2-3 min the membrane potential returned to control level within 1 min. This was followed by a second hyperpolarization of 10-20 mV, which decayed within 15 min. 4. In the absence of extracellular calcium, ATP produced only a brief transient hyperpolarization in aortic endothelium. The plateau and the secondary hyperpolarization were abolished. These findings are consistent with the idea that the changes in membrane potential reflect changes in intracellular free Ca2+ and that the initial peak is due to release of Ca2+ from intracellular stores, whereas the plateau and the secondary hyperpolarization depend on transmembrane Ca2+ influx. 5. Bradykinin evoked potential changes similar to ATP in BAECs, except that the secondary hyperpolarization during wash-out was absent. When the membrane potential was more negative than -80 mV, ATP and bradykinin induced only a small initial hyperpolarization followed by a depolarization of up to 20 mV. 6. In aortic endothelium, ADP (10 microM) evoked a much smaller response than ATP. Adenosine (10 microM), thrombin (2 units/ml), acetylcholine (10 microM) and histamine (10 microM) had only a very small effect on the membrane potential, if any. 7. The amplitude histogram of the membrane potential of GCECs showed only one peak around -35 mV. In coronary endothelium, application of bradykinin, ATP, histamine, thrombin, acetylcholine and adenosine all evoked a transient hyperpolarization of 10-40 mV lasting 1 min or less, which then turned into a depolarization. 8. The K+ channel openers cromakalim (BRL 34915) and lemakalim (BRL 38227) did not affect the membrane potential of GCECs or BAECs.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine↗
PubMedDate not supplied

Neural coding with graded membrane potential changes and spikes.

The neural encoding of sensory stimuli is usually investigated for spike responses, although many neurons are known to convey information by graded membrane potential changes. We compare by model simulations how well different dynamical stimuli can be discriminated on the basis of spiking or graded responses. Although a continuously varying membrane potential contains more information than binary spike trains, we find situations where different stimuli can be better discriminated on the basis of spike responses than on the basis of graded responses. Spikes can be superior to graded membrane potential fluctuations if spikes sharpen the temporal structure of neuronal responses by amplifying fast transients of the membrane potential. Such fast membrane potential changes can be induced deterministically by the stimulus or can be due to membrane potential noise that is influenced in its statistical properties by the stimulus. The graded response mode is superior for discrimination between stimuli on a fine time scale.

Action Potentials↗
PubMed1979

Optical probe responses on sarcoplasmic reticulum: oxacarbocyanines as probes of membrane potential.

The relationship between Ca2+ fluxes and the ion diffusion potential was analyzed on sarcoplasmic reticulum membranes using oxacarbocyanine dyes as optical probes for membrane potential. 3.3'-Diethyloxodicarbocyanine responds to ATP-induced Ca2+ uptake by isolated sarcoplasmic reticulum vesicles with a decrease in absorbance at 600 nm. The optical change is reversed during Ca2+ release from sarcoplasmic reticulum induced by KCl or by ADP and inorganic phosphate. The absorbance changes are largely attributable to the binding of accumulated Ca2+ to the membrane. There is no indication that sustained changes in membrane diffusion potential would accompany pump-mediated Ca2+ fluxes. A large change in the absorbance of 3,3'-diethyloxodicarbocyanine was observed on sarcoplasmic reticulum vesicles under the influence of membrane potential generated by valinomycin in the presence of a K+ gradient or by ionophore A23187 in the presence of a Ca2+ gradient. The maximum of the potential-dependent absorbance change is at 575--580 nm. The potentials generated by valinomycin or ionophore A23187 are short-lived due to the high permeability of sarcoplasmic reticulum membranes for cations and anions. There is no correlation between the direction and magnitude of the artifically imposed membrane potential and the rate of Ca2+ uptake or release by isolated sarcoplasmic reticulum vesicles.

Adenosine Triphosphate↗
PubMed2003

In skeletal muscle the relaxation of the resting membrane potential induced by K(+) permeability changes depends on Cl(-) transport.

In resting skeletal muscle the potassium permeability is determined by the permeability of the inwardly potassium rectifier. Continuous resting membrane potential measurements are done to follow the relaxation of the membrane potential upon changes in potassium permeability. Inhibition of the inwardly potassium rectifier, by extracellular application of 80 microM Ba(2+), causes the cell to depolarize with mean time constants as follows: in control 127+/-7 s ( n=23), in the presence of bumetanide, as an inhibitor of the Na(+)/K(+)/2Cl(-) cotransporter, 182+/-23 s ( n=7), in hypertonic media (340 mosmol/kg) 90.4+/-5 s ( n=7) and in reduced chloride medium 64+/-8 s ( n=5). The depolarizing relaxation of the membrane potential induced by reduction of extracellular potassium produces similar results. These time constants are at least three orders of magnitude slower than the time constants reported in the literature for the inhibition of the inwardly potassium rectifier. Chloride transport affects the relaxation of the membrane potential. A further characterization of chloride transport is done by following the relaxation of the membrane potential upon application of chloride transport modulators. It is argued that the electroneutral cotransporter, for which a flux was preliminarily estimated of 13.4 pmol cm(-2) s(-1), has a considerable role in the processes related to the resting membrane potential.

Animals↗
PubMed2000

Bistable membrane potential of the ciliate Coleps hirtus.

In normal recording solution, the swimming pattern of the freshwater ciliate Coleps hirtus, belonging to the class Prostomatea, consists of alternating periods of nearly linear forward swimming and circular swimming within a small area. Current-clamp recordings were performed to elucidate the mechanism for this behaviour. No members of this class have previously been studied using electrophysiological techniques. The ciliates were maintained in culture and fed on the planctonic alga Rhodomonas minuta. The membrane potential showed spontaneous shifts between a more negative (deep) level of approximately -50 mV and a less negative (shallow) level of approximately -30 mV. The input resistance and capacitance at the more negative level were approximately 400 M capomega and 120 pF respectively. C. hirtus displayed a pronounced inward rectification, which was virtually insensitive to 1 mmol l(-1) Cs(+) and almost completely blocked by 1 mmol l(-1) Ba(2+). Depolarising current injections failed to evoke graded, regenerative Ca(2+) spikes. However, current-induced depolarisations from the more negative potential level (-50 mV) showed a pronounced shoulder during the repolarising phase. Increased current injections prolonged the shoulder, which occasionally stabilised at the shallow membrane potential (-30 mV). The membrane potential could be shifted to the deep level by brief hyperpolarising current injections. Similar biphasic membrane properties have not been reported previously in any ciliate. The bistability of the membrane potential was abolished in Ca(2+)-free solution containing Co(2+) or Mg(2+). In Ca(2+)-free solution containing 1 mmol l(-1) Ba(2+), brief depolarising current injections at the deep potential level evoked all-or-nothing action potentials with a prolonged plateau coinciding with the shallow potential. We conclude that the deep membrane potential in C. hirtus corresponds to the traditional resting potential, whereas the shallow level is a Ca(2+)-dependent plateau potential. In normal solution, the direction of the ciliary beat was backwards at the deep potential level and forwards at the shallow membrane potential, probably reflecting the two main phases of the swimming pattern.

Animals↗
PubMed1987

Na+ modulates the K+ permeability and the membrane potential of alkalophilic Bacillus.

In the absence of Na+ in the medium, the membrane potential of obligately alkalophilic Bacillus cells was found to be decreased by the addition of K+ to the medium, whereas K+ addition in the presence of Na+ had no effect. Rb+ showed essentially the same effect as K+. The decreased membrane potential was quickly restored by lowering the K+ concentration in the medium or by adding Na+ or Li+ to the medium. Thus, in the absence of Na+, the membrane potential of alkalophilic Bacillus seems to be affected by the concentration difference of K+ between inside and outside of the cell, and Na+ or Li+ in the medium suppresses the K+ effect. An exchange between extracellular Rb+ and intracellular K+ was observed in the absence of Na+. However, the exchange was greatly suppressed by the addition of Na+ or Li+ to the medium, indicating that Na+ in the medium modulates the K+ permeability of the alkalophilic Bacillus cell membrane. The K+-induced decrease in the membrane potential of alkalophilic Bacillus in the absence of Na+ is accounted for by the increased K+-permeability of the cell membrane.

Bacillus↗
PubMed1987

Relation between membrane potential and contractile force in smooth muscle of the rat tail artery during stimulation by norepinephrine, 5-hydroxytryptamine, and potassium.

The relation between smooth muscle membrane potential and contractile force was investigated in the rat tail artery to assess the importance of smooth muscle depolarization in the control of smooth muscle tone. Smooth muscle membrane potential and contractile force were measured simultaneously in isolated pieces of rat tail artery exposed to a range of concentrations of norepinephrine, 5-hydroxy-tryptamine, or raised external potassium. Potassium caused depolarization and contraction when the membrane was depolarized beyond -40 mV. Maximum contraction occurred at -19 mV, and further depolarization gave no increase in contraction. Both norepinephrine and 5-hydroxytryptamine caused contraction and depolarization, but the relation between depolarization and contraction was not the same as when potassium was used. There was significant contraction when the membrane potential was more negative than -50 mV, and the membrane potential was around -30 mV during maximal contractions. Although they acted on pharmacologically different membrane receptors, the relation between membrane potential and contraction was the same for norepinephrine and 5-hydroxytryptamine. Prazosin reduced the responses to norepinephrine but did not change the relation between membrane potential and contractile force. These results indicated that norepinephrine and 5-hydroxytryptamine binding to their respective receptors might activate the same sets of intracellular processes that subsequently caused both depolarization and contraction.

Animals↗
PubMed1988

Membrane potential drives organic cation transport into teleost renal proximal tubules.

The relationship between organic cation uptake and basolateral membrane potential was studied in renal tubules from two marine teleost fish, Southern flounder (Paralicthys lethostigma) and killifish (Fundulus heteroclitis). Carrier-mediated uptake of the model organic cation, tetraethylammonium (TEA), increased when K+ was changed from 2.5 to 0.2 mM and decreased when medium K+ was increased to 20 mM. Uptake was also reduced by the K+ channel blocker barium (1 mM). Furthermore, basolateral membrane potential hyperpolarized 15-25 mV in low-K+ medium and depolarized 30-40 mV in high-K+ medium. Barium also depolarized. Finally, basolateral membrane potential was depolarized in a concentration-dependent manner by addition of 100-500 microM TEA or Darstine. Thus treatments that hyperpolarize the basolateral membrane potential increase carrier-mediated TEA uptake, whereas those that depolarize basolateral membrane potential reduce uptake. Furthermore, organic cation transport into tubular cells involves the net influx of positive charge. Together, these findings support the argument that carrier-mediated organic cation uptake at the basolateral membrane is a potential-driven, electrogenic process.

Animals↗
PubMed1990

Actions and interactions of calcium modulators and ethanol on rat atrial membrane potentials.

The effects of ethanol and dihydropyridines on atrial membrane potentials (MP) were studied. Rat atrial strips superfused with Tyrode's solution (36 degrees C) were driven at 5 Hz while recording MP with intracellular microelectrodes. Bay K 8644 7 X 10(-7) M (BAYK) increased the amplitude of the action potential (AAP) without affecting the resting membrane potential (RMP) or the Vmax of phase 0 (Vmax 0). The velocity of change in voltage decreased at the beginning of the repolarization, causing an increase in the action potential duration (APD), but it was not modified at negative voltages. Nimodipine 4.2 X 10(-6) M reduced the AAP without affecting RMP or Vmax 0. The velocity of change in voltage increased at the beginning of the repolarization, causing a decrease in the APD, but was not modified at negative voltages. Ethanol 5.3 X 10(-2) M exerted actions similar to those of nimodipine. Simultaneous exposure to ethanol and nimodipine resulted in changes not different from those obtained with each of the two compounds. The MP remained unchanged when the preparations were exposed to ethanol and BAYK simultaneously. In summary, ethanol and nimodipine exerted similar actions on the atrial MP while BAYK had opposite actions. The effects of ethanol and BAYK cancelled each other.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1997

Resting membrane potential of skeletal muscle calculated from plasma and muscle electrolyte and water contents.

1. A method is described that enables the calculation of resting membrane potential from the electrolyte and water contents in blood plasma and in a sample of human muscle tissue obtained by the percutaneous needle-biopsy technique. In this calculation, the previously described equations for calculating resting membrane potential via the intra- and extra-cellular distribution of chloride were combined with the equation utilizing potassium distribution over the cell membrane. 2. The method of calculation was applied to 60 healthy subjects divided into three groups aged 19-40, 41-60 and 61-85 years. The calculated resting membrane potential in the subjects as a whole was -88.4 mV (SD 1.35; n = 60). A lower value was observed in the group aged 61-85 years (-87.7 mV, SD 1.0; n = 12) than in the group aged 19-40 years (-88.6 mV; SD 1.4; n = 32). No difference was observed between female and male subjects. 3. The RMP calculated with the present method in 60 healthy subjects was also compared with previously published values in healthy subjects, measured by the Clarke electrode method, and with values calculated from electrolyte and water distribution measured by isotope-dilution techniques. The results obtained in healthy subjects with different techniques were very similar. Data were analysed from earlier published studies in experimental animals in which resting membrane potential ranged from -91 to -65 mV. The resting membrane potential calculated from electrolytes in plasma and muscle showed a very good agreement with resting membrane potential recorded directly.

Adult↗