Analysis of receptor reserves in canine tracheal smooth muscle

S. J. Gunst, J. Q. Stropp, N. A. Flavahan

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

The receptor reserves for acetylcholine, 5-hydroxytryptamine, and histamine in canine tracheal muscle were evaluated. Muscle strips were dissected free of epithelial and connective tissue and suspended for isometric tension recording in modified Krebs-Ringer solution. Dissociation constants for all three agonists were determined by analysis of their concentration-response curves under control conditions and after partial inactivation of receptors by phenoxybenzamine dihydrochloride. The values of K(A) for acetylcholine, 5-hydroxytryptamine, and histamine were 1.8 x 10-5 M, 1.35 x 10-6 M, and 5.0 x 10-5 M, respectively. Dissociation constants were used to determine receptor occupancy-response relationships. Maximal responses to acetylcholine were obtained by activation of only 4.0 ± 1.0% of receptors, indicating the presence of a very large receptor-reserve. In contrast, a maximal response to 5-hydroxytryptamine and histamine required activation of 78.0 ± 11.0 and 87.7 ± 1.6% of the receptors, respectively, indicating very modest receptor reserves. The differences in receptor-reserve characteristics for these agonists in airway muscle might contribute to the differential effects of inhibitory and facilitory influences on contractions elicited by them.

Original languageEnglish (US)
Pages (from-to)1755-1758
Number of pages4
JournalJournal of Applied Physiology
Volume62
Issue number4
StatePublished - Jan 1 1987
Externally publishedYes

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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