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Evidence against the temperature‐dependent interconversion of histamine H 1 ‐ and H 2 ‐receptors in the guinea‐pig ileum
Author(s) -
Bertaccini G.,
Zappia L.
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.tb09357.x
Subject(s) - dimaprit , metiamide , histamine , ileum , cimetidine , histamine receptor , histamine h2 receptor , chemistry , receptor , guinea pig , medicine , endocrinology , antagonist , pharmacology , biology , biochemistry
1 The possible temperature‐dependent interconversion of histamine H 1 ‐ and H 2 ‐receptors in the guinea‐pig ileum suggested from previous studies was re‐investigated by use of new and selective H 2 ‐receptor agonists and antagonists. 2 Chlorpheniramine, an H 1 ‐blocker, caused a rightward shift of the cumulative histamine dose‐response curve at both 37°C and 12°C. Conversely cimetidine and tiotidine, two H 2 ‐receptor blockers, were ineffective at both temperatures. Metiamide behaved as a non competitive antagonist at 12°C but only in very high concentrations. 3 Dimaprit and impromidine, two selective H 2 ‐receptor agonists, were inactive at both 37°C and 12°C when given alone, whereas at both temperatures they elicited the already described relaxation of the contractions induced by histamine. 4 Similar results were obtained on the guinea‐pig whole ileum and on the longitudinal muscle strip: this indicates a lack of interference of the circular smooth muscle. 5 Our results allow us to conclude that no temperature‐dependent interconversion of histamine H 1 ‐ and H 2 ‐receptors occurs in the guinea‐pig ileum.