Original Articles

Characterization of histamine receptors in tracheal smooth muscle of Mastomys natalensis

Rakesh Shukla, Rikhab Chand Srimal, Bhola Nath Dhawan

Abstract

The tracheal smooth muscle of Mastomys natalensis contracted with carbachol administration while histamine (H) caused concentration-dependent relaxation. The Specific H2-receptor agonists 4-methyl histamine, dimaprit, impromidine and a high concentration of 2-methyl histamine (H1-agonist) caused relaxation similar to H which was selectively blocked by cimetidine. Low concentrations (10(-5)-10(-4) mol/L) of 2-methyl histamine and of H (10(-8)-10(-7) mol/L) occasionally produced small contractions. Mepyramine (pyrilamine) blocked the contraction but did not modify the relaxant effect of H and its agonists. The results suggest a preponderance of histamine H2-inhibitory receptors in the trachea of this animal.
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