Depression of calcium-dependent potassium conductance of guinea-pig myenteric neurones by muscarinic agonists

Intracellular recordings were made from myenteric neurones of the guinea-pig ileum. Muscarinic agonists acetylcholine (ACh) and oxotremorine reduced membrane potassium conductance (gK). Calcium carried into the neurone by one or more action potentials increased membrane potassium conductance (gK, Ca...

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Bibliographic Details
Published in:The Journal of physiology 1983-09, Vol.342 (1), p.253-266
Main Authors: North, R A, Tokimasa, T
Format: Article
Language:English
Subjects:
Acetylcholine - pharmacology
Action Potentials
Animals
Barium - pharmacology
Biological and medical sciences
Cold Temperature
Dose-Response Relationship, Drug
Fundamental and applied biological sciences. Psychology
Guinea Pigs
In Vitro Techniques
Intestine. Mesentery
Membrane Potentials - drug effects
Myenteric Plexus - metabolism
Myenteric Plexus - physiology
Neurons - metabolism
Neurons - physiology
Oxotremorine - pharmacology
Potassium - metabolism
Time Factors
Vertebrates: digestive system
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Summary:Intracellular recordings were made from myenteric neurones of the guinea-pig ileum. Muscarinic agonists acetylcholine (ACh) and oxotremorine reduced membrane potassium conductance (gK). Calcium carried into the neurone by one or more action potentials increased membrane potassium conductance (gK, Ca). The time course of the muscarinic changes in gK was compared to that of the change in gK, Ca following an action potential. The time course of conductance decrease was similar in both cases, and both time courses had the same temperature coefficient. Concentrations of ACh (100 nM) which were too low to cause a detectable reduction in resting gK shortened the duration of the gK, Ca increase which followed an action potential. Low concentrations of barium (10-100 microM) had the same effect as ACh. This was not due to a reduction in calcium entry during the action potential. Higher concentrations of ACh and barium also reduced resting membrane conductance. The conductance changes during the muscarinic action and the action potential after-hyperpolarization did not add linearly. It is proposed that muscarinic agonists and barium may act by reducing the availability of calcium ions at a site within the membrane which controls gK.
ISSN:0022-3751
1469-7793
DOI:10.1113/jphysiol.1983.sp014849