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Increased Chloride Conductance As the Proximate Cause of Hydrogen Ion Concentration Effects in Aplysia Neurons

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TLDR
A fall in extracellular pH increased membrane conductance of the giant cell in the abdominal ganglion of Aplysia californica and changes of membrane potential were in the direction of the chloride equilibrium potential.
Abstract
A fall in extracellular pH increased membrane conductance of the giant cell in the abdominal ganglion of Aplysia californica. Chloride conductance was trebled whereas potassium conductance was increased by 50%. Half the giant cells were hyperpolarized (2–8 mv) and half were depolarized (3–10 mv) by lowering the pH. The hyperpolarizing response always became a depolarizing response in half-chloride solutions. When internal chloride was increased electrophoretically, the hyperpolarization was either decreased or changed to depolarization. The depolarizing response was reduced or became a hyperpolarizing response after soaking the cell in 10.0 mM chloride, artificial seawater solution for 1 hr. Depolarization was unaffected when either external sodium, calcium, or magnesium was omitted. A glass micropipette having an organic liquid chloride ion exchanger in its tip was used to measure intracellular chloride activity in 14 giant cells; 7 had values of 27.7 ± 1.8 mM (SEM) and 7 others 40.7 ± 1.5 mM. Three of the first group were hyperpolarized when pH was lowered and three of the second group were depolarized. In all six cells, these changes of membrane potential were in the direction of the chloride equilibrium potential. Intracellular potassium activity was measured by means of a potassium ion exchanger microelectrode.

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Carbon dioxide sensitivity and its role in multifunctional neurons in the mollusk Onchidium.

TL;DR: Increased CO2 levels in ASW directly stimulate CO2-sensitive central neurons, promoting ventilation, and results suggest that when dissolved inASW, CO2 directly induced the depolarizing response in Ip-1/2 neurons.
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Intracellular Ca2+ in Helix neurons: Effect of intracellular azide

TL;DR: It was found that the source of Ca2+ involved in enhancement of intracellular activity at exposure to azide at low pH is of extracellular origin, and further that the primary site of action is at the outside of the cell membrane.
References
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Journal ArticleDOI

The influence of potassium and chloride ions on the membrane potential of single muscle fibres.

TL;DR: The most widely accepted theory of the restirng potential of muscle is that the electrical potential difference between the inside and outside of a muscle fibre arises from the concentration gradients of the potassium and chloride ions.
Journal ArticleDOI

Reflexogenic Areas of the Cardiovascular System

TL;DR: Experiments done between 1877 and 1926 showed that a rise of blood pressure in the carotid-cephalic circulation induces bradycardia and a fall of the systemic arterial pressure, while a drop in the vehicle pressure provokes acceleration of the heart rate and a rise in the systemicarterial pressure.
Journal ArticleDOI

Sodium and calcium components of action potentials in Aplysia giant neurone

D. Geduldig, +1 more
TL;DR: Action potentials resulting from direct stimulation can be recorded from the soma of the Aplysia giant neurone in sodium‐free and in calcium‐free external solutions.
Journal ArticleDOI

A Contribution of an Electrogenic Na+ Pump to Membrane Potential in Aplysia Neurons

TL;DR: In an identified cell that shows a marked temperature dependence of RMP, both the potassium equilibrium potential and the membrane resistance were found to be relatively independent of temperature.
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