Antagonism by imidazoline - Type drugs of muscarinic and other receptors in the guinea-pig ileum

M. M. Salazar-Bookaman, Duane Miller, P. N. Patil

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

1 Several imidazolines were examined for the antagonism of muscarinic (M3) and other receptors on the isolated ileum of guinea-pig. The effect of the muscarinic agonist, carbachol was competitively antagonized by oxymetazoline at 10-5 m. A dissociation constant (KB) of 3.6 μm for the antagonist was calculated. At higher concentrations, 3 × 10-5 and 10-4 m, of the antagonist, the agonist dose-response curve was shifted to the right with a decrease in the maximum effect. Thus, a non-competitive block occurred at higher concentrations of oxymetazoline. Blockade of histamine H, and serotonin receptor-mediated responses by oxymetazoline were also of a non-competitive type. 2 Naphazoline at 10-4 m shifted the dose-response curves of carbachol and serotonin to the right by two- and 15-fold, respectively. The maximum contraction of the agonist was not affected. Tolazoline also had a weak antihistaminic activity. At similar concentration; tetrahydrozoline clonidine and phentolamine at 10-5 m produced two-, three- and four-fold shift of the carbachol dose-response curve without significant changes in the maxima. Neither methoxamine, p-amino-clonidine nor cimetidine blocked the responses of carbachol. 3 The isosteric nature of the α-adrenoceptor agonist, oxymetazoline and some imidazolines with carbachol, in part, explains its molecular competition at the muscarinic M3 receptor of the guinea-pig ileum. Surprisingly, contractile effects of carbachol (M3), histamine (H1) or serotonin (5HT3/5HT4) were not influenced by methoxamine, tetrahydrozoline, p-amino clonidine and cimetidine.

Original languageEnglish (US)
Pages (from-to)267-273
Number of pages7
JournalAutonomic and Autacoid Pharmacology
Volume26
Issue number3
DOIs
StatePublished - Jul 2006
Externally publishedYes

Fingerprint

Imidazolines
Carbachol
Muscarinic Receptors
Oxymetazoline
Ileum
Guinea Pigs
Clonidine
Muscarinic M3 Receptors
Pharmaceutical Preparations
Methoxamine
Cimetidine
Serotonin
Tolazoline
Naphazoline
Histamine Receptors
Muscarinic Agonists
Phentolamine
Serotonin Receptors
Adrenergic Receptors
Histamine

All Science Journal Classification (ASJC) codes

  • Pharmacology
  • Neuroscience(all)

Cite this

Antagonism by imidazoline - Type drugs of muscarinic and other receptors in the guinea-pig ileum. / Salazar-Bookaman, M. M.; Miller, Duane; Patil, P. N.

In: Autonomic and Autacoid Pharmacology, Vol. 26, No. 3, 07.2006, p. 267-273.

Research output: Contribution to journalArticle

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