Effects of inorganic salts and of ouabain on some metabolic responses of rat cerebral cortex slices to cationic and electrical stimulations

1968 ◽  
Vol 46 (4) ◽  
pp. 355-362 ◽  
Author(s):  
S. Nakazawa ◽  
J. H. Quastel
Keyword(s):  
Rat Brain ◽  
Potassium Ion ◽  
Ion Concentration ◽  
Magnesium Ions ◽  
High Potassium ◽  
Glycine Uptake ◽  
Ion Concentrations ◽  
Cortex Slices ◽  
Electrical Impulses ◽  
Stimulation Of

The rate of glycine uptake, against a concentration gradient, into rat brain cortex slices, incubated in a physiological glucose medium, is proportional to the sodium ion concentration of the medium and is independent of whether choline chloride or sucrose is used to balance diminished levels of sodium ions. Choline, in contrast to sucrose, resembles sodium in the maintenance of stimulated brain respiration but cannot replace sodium for the stimulation of brain respiration by electrical impulses or by increased potassium ion concentrations. Electrical stimulation of rat brain slices, whilst resembling potassium stimulation in causing a fall in the level of ATP, differs from potassium stimulation in causing no diminution in the rate of glycine transport. This is considered to be due to the operation of two opposing processes: (a) increased glycine influx due to increased influx of sodium, and (b) diminished glycine influx due to a decreased ATP level.The stimulation of rat brain respiration brought about by the application of electrical impulses or by the presence of high potassium ion concentrations, and the uptake of glycine against a concentration gradient, are controlled by the activity of membrane-bound ATPase. This conclusion is supported by the following facts, (a) The presence of potassium ions is needed to obtain the optimal respiratory responses and the optimal rate of glycine uptake; (b) ouabain inhibits the influx of glycine whether the brain tissue is in the stimulated condition or not and it also inhibits stimulated brain respiration; (c) absence of magnesium ions, or a high concentration of magnesium ions, diminishes the effects of high potassium ion concentration or of electrical stimuli on brain respiration; and (d) high concentrations of calcium ions, which block ATPase, inhibit stimulated brain respiration.

Inhibitory effects of ammonium ions and some amino acids on stimulated brain respiration and cerebral amino acid transport

1968 ◽  
Vol 46 (6) ◽  
pp. 543-548 ◽  
Author(s):  
S. Nakazawa ◽  
J. H. Quastel
Keyword(s):  
Brain Cortex ◽  
Methionine Sulfoxide ◽  
Respiratory Response ◽  
Inhibitory Effects ◽  
Ammonium Ions ◽  
High Potassium ◽  
Ion Concentrations ◽  
Brain Cortex Slices ◽  
Cortex Slices ◽  
Electrical Impulses

Ammonium ions cause a suppression of the respiratory response of rat brain cortex slices to electrical stimulation and this is partly reversed by the addition of DL-methionine sulfoxide or L-glutamine but not by addition of L-glutamate or DL-α-methylglutamate. Other basic ions, e.g. tetramethylammonium, pyridine, or pyrimidine, at equivalent concentrations are without effect. Ammonium ions have less inhibitory effect on the respiratory response to high potassium ion concentrations than on that due to application of electrical impulses. They also bring about a marked suppression of the rate of glycine uptake into rat brain cortex slices, the effect being much greater with electrically stimulated brain than with unstimulated brain. Methionine sulfoxide diminishes this suppressive effect. They exercise relatively small inhibitory effects on the depressed rate of glycine uptake obtained in the presence of high potassium ion concentrations. The effect of ammonium ions is considered to be partly due to the fall in cell ATP brought about by the operation of glutamine synthetase. The results are consistent with the view that the extent of stimulation of brain respiration due to electrical impulses or to increased concentration of potassium ions is dependent on the cell level of ATP. L-Glutamate, L-glutamine, or γ-aminobutyrate diminishes the suppressive effects of ammonium ions on glycine influx into brain. L-Glutamate, moreover, diminishes the stimulatory effects of electrical stimulation on brain respiration, lesser effects being produced by L-glutamine or γ-aminobutyrate.

Acetylcholine reversal of potassium inhibition of amino acid transport in rat brain cortex slices

1968 ◽  
Vol 46 (4) ◽  
pp. 363-365 ◽  
Author(s):  
S. Nakazawa ◽  
J. H. Quastel
Keyword(s):  
Amino Acid ◽  
Rat Brain ◽  
Inhibitory Action ◽  
Brain Cortex ◽  
Ion Concentration ◽  
High Potassium ◽  
Rat Brain Cortex ◽  
Brain Cortex Slices ◽  
Glycine Transport ◽  
Cortex Slices

Acetylcholine reverses the inhibitory action of a high potassium ion concentration on glycine uptake into rat brain cortex slices incubated in a physiological Ringer–glucose medium. The effect of acetylcholine, which may take place at 0.02 mM, is enhanced by the presence of eserine which itself is without effect. Choline and hemicholinium at equivalent concentrations are also without effect. The reversing action of acetylcholine is specific, as it cannot reverse the inhibitory action of ammonium ions, ouabain, L-glutamate, or L-glutamine on glycine transport into the brain. As the presence of acetylcholine does not affect the ATP level, it is suggested that it acts by promoting the influx of sodium ions, which have a controlling effect on the amino acid influx.

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.

THE INFLUENCE OF POTASSIUM ION UPON GLUCOSE UPTAKE AND GLYCOGEN SYNTHESIS IN THE ISOLATED RAT DIAPHRAGM

1955 ◽  
Vol 33 (1) ◽  
pp. 687-694 ◽  
Author(s):  
D. W. Clarke
Keyword(s):  
Glucose Uptake ◽  
Glycogen Synthesis ◽  
Potassium Ion ◽  
Ion Concentration ◽  
Rat Diaphragm ◽  
High Potassium ◽  
High Concentrations ◽  
Glycogen Breakdown ◽  
Isolated Rat

The amounts of glucose taken from a medium, and the amounts of glycogen synthesized, by rat hemidiaphragms were studied under various conditions. High concentrations of potassium ion inhibited the glucose uptake and there was also a reduced net glycogen synthesis. Glycogen breakdown was probably not increased by high potassium ion concentration. The effect of potassium was most marked when conditions were such that one would ordinarily expect a considerable glucose uptake or glycogen synthesis. The action of insulin was not peculiarly susceptible to potassium ion inhibition.

scholarly journals Anomalous Rectification in the Squid Giant Axon Injected with Tetraethylammonium Chloride

1965 ◽  
Vol 48 (5) ◽  
pp. 859-872 ◽  
Author(s):  
Clay M. Armstrong ◽  
Leonard Binstock
Keyword(s):  
Action Potential ◽  
Outward Current ◽  
Giant Axon ◽  
Potassium Ion ◽  
Ion Concentration ◽  
High Potassium ◽  
Tetraethylammonium Chloride ◽  
Voltage Curve ◽  
Instantaneous Current ◽  
Current Voltage Curve

The injection of tetraethylammonium chloride into the giant axon of the squid prolongs the action potential and eliminates most of the late current under voltage-clamp. Experiments on fibers in an external medium of high potassium ion concentration demonstrate that injected tetraethylammonium chloride causes rectification of the instantaneous current-voltage curve for potassium by excluding outward current. This interference with the flow of outward potassium ion current underlies the prolongation of the action potential seen in tetraethylammonium-injected fibers.

BIOCHEMICAL STUDIES ON CHLORPROMAZINE: 2. EFFECTS OF CHLORPROMAZINE ON INCORPORATION INTO PROTEINS, AND BREAKDOWN OF GLYCINE-1-C14BY ISOLATED RAT BRAIN CORTEX

1957 ◽  
Vol 35 (1) ◽  
pp. 1145-1150 ◽  
Author(s):  
O. Lindan ◽  
J. H. Quastel ◽  
S. Sved
Keyword(s):  
Rat Brain ◽  
Brain Cortex ◽  
Experimental Conditions ◽  
Rat Brain Cortex ◽  
Brain Cortex Slices ◽  
High Concentrations ◽  
Cortex Slices ◽  
The Given ◽  
The Brain ◽  
Stimulation Of

Glycine is decomposed in rat brain cortex to yield carbon dioxide. This process, in which C14O2is formed from glycine-1-C14, is markedly stimulated by the presence of 10 mM glucose, the rate of production of C14O2being increased at least threefold. The presence of succinate exercises a much smaller stimulation of C14O2formation. The addition of KCl (0.1 M) or of 2,4-dmitrophenol (0.025 mM), whilst stimulating the rate of oxygen uptake, does not increase the rate of C14O2formation from glycine-1-C14. The addition of K+tends to diminish the rate. The process of glycine-1-C14breakdown to C14O2is almost insensitive to chlorpromazine, under the given experimental conditions, until relatively high concentrations (e.g. 0.6 mM) are used. The presence of chlorpromazine, however, brings about an inhibition of the rate of glycine-1-C14incorporation into rat brain cortex proteins, an inhibition of 20% being recorded at a concentration of the drug (0.2 mM) that has little or no effect on the respiration of the brain or on the rate of breakdown of glycine-1-C14into C14O2. Glycine incorporation into brain cortex proteins is a process relatively sensitive to chlorpromazine, the magnitude of inhibition being of the same order as that brought about by amytal at similar concentrations. It is suggested that chlorpromazine brings about its effects by an uncoupling of phosphorylation from oxidation in brain cortex slices.

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