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A study of the histamine H 2 ‐receptor mediating relaxation of the parenchymal lung strip preparation of the guinea‐pig
Author(s) -
Foreman J.C.,
Rising T.J.,
Webber S.E.
Publication year - 1985
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1985.tb08916.x
Subject(s) - dimaprit , mepyramine , histamine , guinea pig , tachyphylaxis , muscarinic acetylcholine receptor , forskolin , endocrinology , propranolol , medicine , chemistry , antagonist , dissociation constant , cimetidine , atropine , receptor , histamine h2 receptor , biology
1 The relaxation produced by several H 2 ‐receptor agonists and forskolin was investigated on strips of guinea‐pig lung parenchyma. 2 Dimparit, 1 μM to 10 mM, 4‐methyl histamine, 0.5 μM to 100 μM and impromidine, 10 nM to 1 μM, had no effect on the tone of the unstimulated strips of lung parenchyma but caused a dose‐dependant relaxation of strips that were contracted by 2‐pyridylethylamine (2‐PEA), 15 μM. Forskolin, 10 nM to 4 μM, produced a dose‐dependent relaxation of both the stimulated and unstimulated lung strips. 3 The muscarinic antagonist atropine, 1 μM, and the β 2 ‐adrenoceptor antagonist propranolol, 10 μM, had no effect on the dose‐response curve for dimaprit‐induced relaxation of the lung strip. 4 The dose‐response curve for dimaprit was shifted to the right in a dose‐dependent manner by increasing concentrations of a variety of H 2 ‐antagonists. Schild plots produced a straight line for all the H 2 ‐antagonists with slopes not significantly different from unity. The equilibrium dissociation constants for the H 2 ‐antagonists on the lung strip preparation were similar to those previously reported for inhibition of the chronotropic activity of histamine on guinea‐pig right atria and inhibition of [ 3 H]‐tiotidine binding to homogenates of guinea‐pig lung parenchyma.