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Biomedical subjects

N Takeuchi

Publications and source records attributed to N Takeuchi.

At least 379 records · Page 21Linked to original sources
PubMed1971

Anion interaction at the inhibitory post-synaptic membrane of the crayfish neuromuscular junction.

1. The membrane potential and the membrane conductance of the crayfish muscle fibre in solutions containing various anions were measured with intracellular micro-electrodes.2. When Cl(-) in the solution was replaced by Br(-), NO(3) (-), I(-) or CNS(-), the addition of gamma-amino butyric acid (GABA) produced a transient hyperpolarization of the membrane.3. The reversal potential of the inhibitory junctional potentials (i.j.p.s) was at a slightly depolarized level relative to the resting potential in the normal Cl(-) solution. When Cl(-) in the bathing solution was replaced by foreign anions, the reversal potential shifted towards the hyperpolarized level. The hyperpolarization was in the order CNS(-) > I(-) > NO(3) (-) > Br(-).4. When a part of Cl(-) in the bathing solution was substituted by Br(-), the inhibitory membrane conductance activated by GABA was increased as the concentration of Br(-) increased. The inhibitory membrane conductance decreased when one quarter or a half of Cl(-) was replaced by CNS(-), NO(3) (-) or I(-), but it increased again in higher concentrations of these anions.5. Ca(2+), Mg(2+) and Ba(2+) showed no appreciable effect on the inhibitory membrane conductance activated by GABA, while they decreased the conductance of the resting muscle membrane.6. It was suggested that, at the activated inhibitory membrane, there is an interaction between anions and the permeability of Cl(-) is decreased by the presence of foreign anions, such as CNS(-), I(-) and NO(3) (-). The present results support the idea that the activated inhibitory membrane is charged positively and anions penetrate the membrane interacting with the charge sites.

Aminobutyrates↗
PubMed1971

Variations in the permeability properties of the inhibitory post-synaptic membrane of the crayfish neuromuscular junction when activated by different concentrations of GABA.

1. The membrane conductance of the crayfish muscle was measured with intracellular micro-electrodes. Increase in the membrane conductance induced by various concentrations of gamma-amino butyric acid (GABA) was measured in the Br(-), NO(3) (-), I(-) and CNS(-) solutions and compared with that in Cl(-) solution. When the membrane was activated by lower concentrations of GABA, the resulting membrane conductance in NO(3) (-) and I(-) solutions was larger than in Cl(-) solution, while the membrane conductance activated by higher concentrations in NO(3) (-) and I(-) solutions were smaller than in Cl(-) solution. The membrane conductance activated by GABA was larger in Br(-) solution and smaller in CNS(-) solution than the membrane conductance activated in Cl(-) solution, throughout the concentration range of GABA examined.2. The reversal potential of inhibitory junctional potentials (i.j.p.s) was measured shortly after replacing Cl(-) by foreign anions: Br(-), NO(3) (-), I(-) and CNS(-). In I(-) solution the i.j.p.s produced by lower stimulation frequencies showed a reversal potential at a more hyperpolarized level than those produced by higher stimulation rates.3. Shortly after replacing Cl(-) by I(-), the GABA potential induced by iontophoretic application showed a triphasic potential change at the ;reversal' potential. The reversal level of the GABA potential produced by smaller doses was at a more hyperpolarized level than that produced by larger doses.4. Possibilities of a concentration effect of GABA are discussed. It is suggested that the relative permeability of the crayfish inhibitory membrane to anions changes depending on the concentration of GABA.

Aminobutyrates↗
PubMed1969

A study of the action of picrotoxin on the inhibitory neuromuscular junction of the crayfish.

1. The effect of picrotoxin on the neuromuscular junction of the crayfish (Cambarus clarkii) was investigated. The potential changes were recorded intracellularly and extracellularly with micro-electrodes. The membrane conductance of the muscle fibre was also measured.2. Picrotoxin depressed the amplitudes of the inhibitory junctional potentials and the potential changes produced by iontophoretically applied gamma-aminobutyric acid (GABA), but had no appreciable effect on the excitatory junctional potentials and the potential changes produced by L-glutamate.3. The presynaptic action of GABA and the neural transmitter was depressed by picrotoxin. The presynaptic action of beta-guanidinopropionic acid was also depressed by picrotoxin.4. The increase in the membrane conductance produced by the addition of GABA in the bath fluid was depressed by picrotoxin. The dose-response relation showed that picrotoxin depressed the conductance increase produced by GABA in a non-competitive manner. The action of picrotoxin on the conductance increase produced by GABA was more effective in low Cl- solution.5. The analysis of the dose-response curves showed that the action of picrotoxin was well expressed by the Michaelis-Menten equation, but the slope of the dose-response curve of GABA was steeper than this relation. It is proposed that the conductance of the junctional membrane was increased by the combination of two molecules of GABA with a receptor, and the attachment of one molecule of picrotoxin to a specific site depressed the conductance increase.

Aminobutyrates↗