scholarly journals Control of synthesis and release of radioactive acetylcholine in brain slices from the rat. Effects of neurotropic drugs

1973 ◽  
Vol 132 (1) ◽  
pp. 1-14 ◽  
Author(s):  
D. S. Grewaal ◽  
J. H. Quastel
Keyword(s):  
Incubation Medium ◽  
Acetylcholine Release ◽  
Brain Slices ◽  
High Concentration ◽  
Choline Transport ◽  
Acetylcholine Synthesis ◽  
High K ◽  
Blocking Effects ◽  
Release Of Acetylcholine ◽  
Cortex Slices

1. Studies of the synthesis and release of radioactive acetylcholine in rat brain-cortex slices incubated in Locke–bicarbonate–[U-14C]glucose media, containing paraoxon as cholinesterase inhibitor, revealed the following phenomena: (a) dependence of K+-or protoveratrine-stimulated acetylcholine synthesis and release on the presence of Na+ and Ca2+ in the incubation medium, (b) enhanced release of radioactive acetylcholine by substances that promote depolarization at the nerve cell membrane (e.g. high K+, ouabain, protoveratrine, sodium l-glutamate, high concentration of acetylcholine), (c) failure of acetylcholine synthesis to keep pace with acetylcholine release under certain conditions (e.g. the presence of ouabain or lack of Na+). 2. Stimulation by K+ of radioactive acetylcholine synthesis was directly proportional to the external concentration of Na+, but some synthesis and release of radioactive acetylcholine occurred in the absence of Na+ as well as in the absence of Ca2+. 3. The Na+ dependence of K+-stimulated acetylcholine synthesis was partly due to suppression of choline transport, as addition of small concentrations of choline partly neutralized the effect of Na+ lack, and partly due to the suppression of the activity of the Na+ pump. 4. Protoveratrine caused a greatly increased release of radioactive acetylcholine without stimulating total radioactive acetylcholine synthesis. Protoveratrine was ineffective in the absence of Ca2+ from the incubation medium. It completely blocked K+ stimulation of acetylcholine synthesis and release. 5. Tetrodotoxin abolished the effects of protoveratrine on acetylcholine release. It had blocking effects (partial or complete) on the action of high K+, sodium l-glutamate and lack of Ca2+ on acetylcholine synthesis and release. 6. Unlabelled exogenous acetylcholine did not diminish the content of labelled tissue acetylcholine, derived from labelled glucose, suggesting that no exchange with vesicular acetylcholine took place. In the presence of 4mm-KCl it caused some increase in the release of labelled acetylcholine. 7. The barbiturates (Amytal, pentothal), whilst having no significant effects on labelled acetylcholine synthesis in unstimulated brain except at high concentration (1mm), diminished or abolished (at 0.25 or 0.5mm) the enhanced release of acetylcholine, due to high K+ or lack of Ca2+. The fall in tissue content of acetylcholine, due to lack of Ca2+, was diminished or abolished by pentothal (0.25 or 0.5mm) or Amytal (0.25mm).

scholarly journals Effects of tetrodotoxin and anaesthetics on brain metabolism and transport during anoxia

1972 ◽  
Vol 126 (4) ◽  
pp. 851-867 ◽  
Author(s):  
R. Shankar ◽  
J. H. Quastel
Keyword(s):  
Action Potentials ◽  
Brain Cortex ◽  
Aerobic Glycolysis ◽  
Rat Kidney ◽  
Brain Slices ◽  
Anaerobic Glycolysis ◽  
High Concentration ◽  
Adult Rats ◽  
Brain Cortex Slices ◽  
Cortex Slices

1. Tetrodotoxin, at concentrations at which it abolishes generation of action potentials in the nervous system, enhances by about 300% the rate of anaerobic glycolysis of brain-cortex slices from adult rats, or from adult and infant guinea pigs. This occurs to a greater extent in Ca2+-deficient incubation media than in Ca2+-rich media. Tetrodotoxin has no accelerative effect on cerebral aerobic glycolysis. 2. Tetrodotoxin does not affect the rate of anaerobic glycolysis of 2-day-old rat brain-cortex slices, nor that of adult rat kidney medulla, nor that of an extract of an acetone-dried powder of brain. 3. Tetrodotoxin does not affect the rate of penetration of glucose into brain slices. 4. Its effect is not apparent if it is added 10min or later after the onset of anoxia. 5. Its effect diminishes as the concentration of K+ in the incubation medium is increased while that of Na+ is decreased. 6. Its salient effect, at the onset of anoxia, is to diminish influx of Na+ into, and efflux of K+ from, the brain slices. 7. Substances that promote cerebral influx of Na+, e.g. protoveratrine, sodium l-glutamate, diminish the accelerative action of tetrodotoxin. 8. It is concluded that tetrodotoxin exerts its effect on anaerobic glycolysis by suppressing, at the onset of anoxia, the generation of action potentials and thereby the accompanying influx of Na+ and efflux of K+. It is suggested that glycolytic stimulation occurs because a rate-limiting step, e.g. operation of pyruvate kinase, is stimulated by K+ and depressed by Na+. 9. Local anaesthetics behave in a manner similar to that of tetrodotoxin in enhancing cerebral anaerobic glycolysis. 10. Sodium Amytal has a marked effect at relatively high concentration. 11. Tetrodotoxin diminishes efflux of amino acids, particularly glutamate and aspartate, at the onset of anoxia.

scholarly journals Relation between the content of acetyl-coenzyme A and acetylcholine in brain slices

1980 ◽  
Vol 188 (3) ◽  
pp. 683-688 ◽  
Author(s):  
J Rícný ◽  
S Tucek
Keyword(s):  
Incubation Medium ◽  
Brain Slices ◽  
Mass Action ◽  
Direct Relation ◽  
Law Of Mass Action ◽  
Acetyl Coa ◽  
Caudate Nuclei ◽  
High K ◽  
State Concentration

Slices of rat caudate nuclei were incubated in vitro in media containing, among other constituents, three different concentrations of glucose (0.5, 2 and 10 mM), 0.2 mM-choline, paraoxon as an inhibitor of cholinesterase, and 5 mM- or 30 mM-K+. After 30 and 60 min of incubation, the concentrations of acetyl-CoA, acetylcholine and choline in the tissue and of acetylcholine in the incubation medium were measured. The content of acetyl-CoA in the sliced varied in direct relation to the concentration of glucose in the incubation medium. The content of acetylcholine in the slices and, in experiments with high K+, also the amount of acetylcholine released into the incubation medium varied in direct relation to the concentration of glucose in the incubation medium and to the concentration of acetyl-CoA in the slices; the relation between the concentrations of acetyl-CoA and of acetylcholine in the slices was linear. It was concluded that the availability of acetyl-CoA had a decisive influence on both the rate of synthesis of acetylcholine and its steady-state concentration. The observations accord with the view that, at the ultimate level, the synthesis of acetylcholine is controlled by the Law of Mass Action.

Effects of acetylcholine on potassium-induced changes of water and sodium uptakes in cerebral cortex slices from the rat

1977 ◽  
Vol 55 (3) ◽  
pp. 339-346 ◽  
Author(s):  
A. M. Benjamin ◽  
J. H. Quastel
Keyword(s):  
Calcium Ions ◽  
Incubation Medium ◽  
Physiological Saline ◽  
Brain Cell ◽  
Potassium Ions ◽  
Sodium Ions ◽  
High Concentration ◽  
High Concentrations ◽  
Cortex Slices ◽  
A Site

The increases in uptakes of water and of sodium ions that occur in rat brain cortex slices when they are incubated in a physiological saline – glucose medium in presence of a high concentration of potassium ions (105 μequiv./ml) are abolished by acetylcholine in presence of eserine but not by choline. Acetylcholine is effective at 20 μM but its optimal effect occurs at about 0.7 mM. Its action is suppressed by atropine and not by d-tubocurarine. The potassium-induced change of permeability of brain cell membranes to sodium ions occurs at a site different from the tetrodotoxin-sensitive channel of sodium entry, because the suppressive effects of acetylcholine and tetrodotoxin are apparently independent of each other. The acetylcholine effect does not occur in the absence of calcium ions from the incubation medium. It is suggested that the increase of cell calcium ions, brought about by high concentrations of potassium ions in the incubation medium, induces an increase of glial permeability to sodium ions, with a resultant change in the sodium gradient, and that this increase is suppressed by acetylcholine.

Effects of Cerebral Stimuli on Adenine Incorporation into Nucleotides and RNA in Brain Slices from the Rat

1972 ◽  
Vol 50 (6) ◽  
pp. 672-683 ◽  
Author(s):  
N. B. Glick ◽  
J. H. Quastel
Keyword(s):  
Brain Tissue ◽  
Incubation Medium ◽  
Rna Synthesis ◽  
Brain Cortex ◽  
Specific Activity ◽  
Brain Slices ◽  
Brain Cortex Slices ◽  
Specific Activities ◽  
Cortex Slices ◽  
The Brain

Comparisons have been made of the rates of incorporation of [8-14C]adenine into RNA and of the specific activities of labelled ATP, in rat brain cortex slices incubated under conditions affecting nucleotide and RNA synthesis.The presence of 50 mM KCl in the incubation medium causes a considerable reduction of the rate of [8-14C]-adenine incorporation into RNA, with no diminution of the specific activity of the cerebral ATP or of the rate of nucleotide formation from adenine. It is inferred that cerebral RNA synthesis is suppressed by 50 mM KCl in the incubation medium.When K+ is omitted from the incubation medium or in the presence of 198 mM NaCl or 5 mM sodium L-glutamate, both the rate of [8-14C]adenine incorporation into RNA and the specific activity of cerebral ATP are diminished to approximately the same extent. This suggests that the process of RNA synthesis in the brain tissue is but little affected either by the increased ceil concentration of Na+ or by the diminished ATP concentration that obtain under these incubation conditions. The process, however, of [8-14C]adenine incorporation into cell nucleotides is markedly suppressed.The presence of protoveratrine (10 μM) causes at least 40% reduction in the rates of [8-14C]adenine incorporation into both RNA and nucleotides with little reduction in the specific activity of the cerebral ATP. The effects of protoveratrine are abolished by tetrodotoxin, indicating that the effects of protoveratrine are confined to the neurons.It is concluded that reductions of the specific activity of cerebral ATP derived from labelled adenine are due to the diminished rates of nucleotide formation from adenine that occur under specific incubation conditions. Such reductions may give rise to the observed diminutions in the rates of incorporation of labelled adenine into RNA. The relatively small fail in the specific activity of isolated ATP after incubation of brain tissue in the presence of protoveratrine is attributed to the localization of the effects of this drug to the neurons, in which the content and specific activity of ATP are suppressed, while those in the glia are undiminished.

scholarly journals Uptake and release of glutamate in cerebral-cortex slices from the rat

1972 ◽  
Vol 128 (5) ◽  
pp. 1117-1124 ◽  
Author(s):  
K. Okamoto ◽  
J. H. Quastel
Keyword(s):  
Cerebral Cortex ◽  
Glucose Metabolism ◽  
Rat Brain ◽  
Incubation Medium ◽  
Brain Slices ◽  
Aerobic Incubation ◽  
Extracellular Glutamate ◽  
Cortex Slices ◽  
Almost All ◽  
Uptake And Release

1. Cerebral-cortex slices from rat brain, loaded with labelled l-glutamate as a result of aerobic incubation with labelled glucose, lost less than 15% of this glutamate on subsequent incubation in the presence of unlabelled glucose and l-glutamate. This indicates that very little exchange occurs between extracellular l-glutamate and glutamate accumulated in the neurons as a result of glucose metabolism. 2. Slices, loaded with labelled l-glutamate as a result of aerobic incubation in a medium containing unlabelled glucose and labelled l-glutamate, lost more than half of this glutamate on subsequent incubation in the presence of unlabelled l-glutamate. This indicates that exchange occurs between extracellular glutamate and glutamate accumulated in brain slices as a result of its uptake from the incubation medium. 3. Evidence was obtained suggesting that only a part of the glutamate, accumulated in brain slices as a result of its uptake from an incubation medium containing both glucose and l-glutamate, entered the neurons; apparently almost all the rest entered the glia. 4. It is concluded that the slices contain a pool of glutamate, derived from glucose and located in the neurons, which is poorly exchangeable with extracellular glutamate, and another pool of glutamate, derived from extracellular glutamate and located in the glia, which is freely exchangeable with extracellular glutamate.

scholarly journals Therapeutic use of botulinum toxin in pain treatment

2018 ◽  
Vol 2 (3) ◽  
Author(s):  
Raj Kumar
Keyword(s):  
Chronic Pain ◽  
Nervous System ◽  
Botulinum Toxin ◽  
Acetylcholine Release ◽  
Pain Treatment ◽  
Muscle Relaxation ◽  
Cholinergic Synapse ◽  
Systems Research ◽  
Release Of Acetylcholine ◽  
Myofascial Syndrome

Botulinum toxin is one of the most potent molecule known to mankind. A neurotoxin, with high affinity for cholinergic synapse, is effectively capable of inhibiting the release of acetylcholine. On the other hand, botulinum toxin is therapeutically used for several musculoskeletal disorders. Although most of the therapeutic effect of botulinum toxin is due to temporary skeletal muscle relaxation (mainly due to inhibition of the acetylcholine release), other effects on the nervous system are also investigated. One of the therapeutically investigated areas of the botulinum neurotoxin (BoNT) is the treatment of pain. At present, it is used for several chronic pain diseases, such as myofascial syndrome, headaches, arthritis, and neuropathic pain. Although the effect of botulinum toxin in pain is mainly due to its effect on cholinergic transmission in the somatic and autonomic nervous systems, research suggests that botulinum toxin can also provide benefits related to effects on cholinergic control of cholinergic nociceptive and antinociceptive systems. Furthermore, evidence suggests that botulinum toxin can also affect central nervous system (CNS). In summary, botulinum toxin holds great potential for pain treatments. It may be also useful for the pain treatments where other methods are ineffective with no side effect(s). Further studies will establish the exact analgesic mechanisms, efficacy, and complication of botulinum toxin in chronic pain disorders, and to some extent acute pain disorders.

Ammonia toxicity and cerebral oxidative metabolism

1961 ◽  
Vol 200 (3) ◽  
pp. 420-424 ◽  
Author(s):  
Guy M. McKhann ◽  
Donald B. Tower
Keyword(s):  
Oxidative Metabolism ◽  
Incubation Medium ◽  
Lactic Acid Production ◽  
Ammonia Toxicity ◽  
Thiamine Pyrophosphate ◽  
Oxidative Decarboxylation ◽  
Cortex Slices ◽  
The Brain ◽  
Cat Cerebral Cortex

Effects of NH4Cl on oxidative metabolism of cat cerebral cortex slices and mitochondria incubated in vitro were studied. In slices, addition of 10 mm NH4Cl to the incubation medium resulted in significant (16%) reduction of O2 uptake, doubling of lactic acid production and marked increase of glucose utilization compared to control slices. Mitochondria showed a 30–40% decrease of O2 consumption in the presence of 15 mm NH4Cl when pyruvate or α-ketoglutarate were substrates, but little if any difference from controls with succinate, glutamic acid or γ-aminobutyric acid as substrates. Pyruvate utilization by ammonia-treated mitochondria was inhibited to the same degree as O2 consumption and was not increased by supplementing the incubation medium with excess succinate. Additions of α-lipoic acid, thiamine pyrophosphate or DPN to such preparations failed to reverse the NH4Cl effect. Satisfactory P/O ratios were obtained for all mitochondrial preparations. It is concluded that a primary toxic effect of ammonia on the brain may be direct interference with oxidative decarboxylation of pyruvic and α-ketoglutaric acids.

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