Effect of 2-nicotinamidethyl nitrate (SG-75) on the membrane potential of left atrial muscle fibres of the dog - Increase in potassium conductance

T. Yanagisawa, N. Taira

Research output: Contribution to journalArticlepeer-review

90 Citations (Scopus)

Abstract

1. 2-Nicotinamidethyl nitrate (SG-75) (10-6-10-4 mol/l) and methacholine (MeCh) (10-7-10-5 mol/l) hyperpolarized the resting membrane potential, and produced increases in amplitude and maximum rate of rise and a decrease in duration of the action potential of left atrial muscle fibres of the dog. 2. Changes in membrane potentials produced by SG-75 were not modified by atropine at a concentration (3×10-7 mol/l) which greatly antagonized those induced by MeCh. 3. The decrease in resting membrane potential for a 10-fold increase in extracellular K+ concentration ([K+]0) was greater in the presence than in the absence of SG-75 or MeCh. 4. SG-75- and MeCh-induced changes in membrane potentials were not affected by the replacement of NaCl by Na isethionate in perfusion fluid. 5. SG-75- and MeCh-induced changes in membrane potentials were not modified by ouabain (10-6 mol/l). 6. The "slow response" of left atrial muscle fibres was obtained by increasing the [K+]0 to 27 mM in the presence of isoprenaline (10-6 mol/l). SG-75 and MeCh primarily produced a decrease in duration of the "slow response". At higher concentrations SG-75 and MeCh hyperpolarized the resting membrane potential and decreased the amplitude and maximum rate of rise of the "slow response". Unlike SG-75 and MeCh, verapamil primarily decreased the amplitude and maximum rate of rise of the "slow response" without changes in duration of the "slow response" and resting membrane potential. 7. The above results suggest that the mechanism of action of SG-75 on left atrial muscle fibres may be an increase in potassium conductance of the membrane without mediation through muscarinic receptors.

Original languageEnglish
Pages (from-to)69-76
Number of pages8
JournalNaunyn-Schmiedeberg's Archives of Pharmacology
Volume312
Issue number1
DOIs
Publication statusPublished - 1980 May 1

Keywords

  • 2-Nicotinamidethyl nitrate (SG-75)
  • Atrial muscle
  • Membrane potential
  • Methacholine
  • Potassium conductance

ASJC Scopus subject areas

  • Pharmacology

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