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H 1 ‐histamine receptors may mediate the contractile response of guinea‐pig ileum to ‘histamine‐free’ splenic extracts
Author(s) -
Ainz L.F.,
Casis E.,
Gandarias J.M.,
GilRodrigo C.E.,
Gandarias J.J. Goiriena
Publication year - 1983
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.1476-5381.1983.tb11009.x
Subject(s) - histamine , diphenhydramine , ileum , medicine , guinea pig , endocrinology , histamine receptor , chemistry , antagonist , histamine h1 antagonists , methysergide , pharmacology , receptor , biology
1 A water‐soluble splenic factor, which produces a contractile response of the guinea‐pig ileum, that is resistant to cholinoceptor and adrenoceptor antagonists is described. 2 The ileal contractions elicited by the splenic extract showed some significant differences from those elicited by 5‐hydroxytryptamine. The responses to splenic extract were not affected by the D‐tryptamine‐receptor antagonist, methysergide. 3 The effect of the splenic extract on the guinea‐pig ileum was similar to that of histamine. The H 1 ‐histamine antagonists, (+)‐chloropheniramine and diphenhydramine, caused a parallel shift to the right of the splenic extract dose‐response curve without suppression of the maximum response. A pA 2 value of 8.97 ± 0.03 for (+)‐chlorpheniramine and 7.55 ± 0.1 for diphenhydramine was calculated. 4 Significant histamine levels, as determined by fluorometric methods, could not be detected in the splenic extract. Likewise, the splenic factor did not release histamine from the intestinal preparation. 5 These results support the view that: (i) the splenic factor acts through H 1 ‐histamine receptors; (ii) it is not histamine; (iii) it does not have any histamine releasing effect on the ileal smooth muscle.