Modulation of canine antral circular smooth muscle by acetylcholine, noradrenaline and pentagastrin

T. Y. El Sharkawy, J. H. Szurszewski

Research output: Contribution to journalArticle

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Abstract

The effects of acetylcholine, noradrenaline and pentagastrin on the action potential of canine antral circular muscle were determined using the intracellular micro-electrode technique. Acetylcholine increased the amplitude and duration of the plateau potential of the action potential. Since these effects were blocked by atropine but not by hexamethonium, the effects of acetylcholine were on muscarinic receptors, probably located on the smooth muscle cell. Pentagastrin 2 x 10-10 M increased the size of the plateau potential and the frequency of the action potential; pentagastrin 1 x 10-9 M increased the frequency of the action potential complex and produced a marked diastolic depolarization between action potentials. The effect on the size of the plateau potential was biphasic. The amplitude and half-time duration of the plateau potential increased in the first 3 min, but thereafter, during steady-state conditions, they were the same as or slightly greater than those obtained in Krebs solution. All the effects produced by pentagastrin were due to a direct action on the smooth muscle cell. Noradrenaline decreased the size of the plateau potential but increased its frequency; high concentrations (> 10-5 M) additionally produced a diastolic depolarization between action potentials. These effects were mediated primarily by α-adrenoceptors presumably located on the smooth muscle cell. It was concluded that the substances studied primarily alter the size of the plateau potential in antral circular muscle. Since phasic contractions are associated with the plateau potential, it is suggested that agents which increase the size of the plateau potential increase the force of the contraction whereas agents which decrease the size of the plateau potential have the opposite effect.

Original languageEnglish (US)
Pages (from-to)309-320
Number of pages12
JournalJournal of Physiology
VolumeVol. 279
StatePublished - 1978

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Pentagastrin
Action Potentials
Acetylcholine
Smooth Muscle
Canidae
Norepinephrine
Smooth Muscle Myocytes
Muscles
Hexamethonium
Muscarinic Receptors
Atropine
Adrenergic Receptors
Antral
Electrodes

ASJC Scopus subject areas

  • Physiology

Cite this

Modulation of canine antral circular smooth muscle by acetylcholine, noradrenaline and pentagastrin. / El Sharkawy, T. Y.; Szurszewski, J. H.

In: Journal of Physiology, Vol. Vol. 279, 1978, p. 309-320.

Research output: Contribution to journalArticle

El Sharkawy, T. Y. ; Szurszewski, J. H. / Modulation of canine antral circular smooth muscle by acetylcholine, noradrenaline and pentagastrin. In: Journal of Physiology. 1978 ; Vol. Vol. 279. pp. 309-320.
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