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EFFECTS OF CICLETANINE ON HISTAMINE‐INDUCED CONTRACTIONS OF ISOLATED RABBIT MESENTERIC ARTERIES
Author(s) -
EBEIGBE A.B.,
CABANIE M.,
GODFRAIND T.
Publication year - 1989
Publication title -
fundamental and clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.655
H-Index - 73
eISSN - 1472-8206
pISSN - 0767-3981
DOI - 10.1111/j.1472-8206.1989.tb00453.x
Subject(s) - histamine , antagonism , nifedipine , chemistry , mesenteric arteries , dissociation constant , cimetidine , endocrinology , medicine , pharmacology , calcium , receptor , artery , biochemistry , organic chemistry
Summary— The antagonism by cicletanine of contractile responses to histamine has been examined in vitro on ring preparations of rabbit mesenteric arteries. Cicletanine (10‐ 8 –10 −6 M) caused a parallel rightward shift of histamine concentration response curve, with a pA 2 value of 7.48 (slope = 0.89 ± 0.19, not significantly different from unity). Histamine‐induced contractions were nifedipine‐sensitive and associated with cicletanine‐sensitive increased 45 Ca uptake. Endothelium removal resulted in enhanced contractile responses to histamine, but did not significantly modify cicletanine‐induced antagonism: K B (dissociation constant) values for cicletanine antagonism in the presence or absence of endothelium were: 3.7 (± 0.1)x 10 −8 M and 3.6 (± 0.3)x 10 −8 M, respectively. Cicletanine (>10 −4 M) also significantly attenuated 10 mM caffeine‐induced contractions in rings exposed to Ca‐free 100 mM K+ depolarizing medium. The results suggest that cicletanine‐induced antagonims of histamine H 1 receptor‐mediated contractions of rabbit mesenteric arteries is associated with interference with calcium entry as well as at high concentrations, release from intracellular stores.