The effects of histamine and some histamine-like agonists on blood pressure in the cat.
1. The effects of histamine on blood pressure have been compared with the effects caused by four histamine-like agonists in anaesthetized cats. 2. It has been confirmed that the depressor responses to histamine involve both H1- and H2-receptors: depressor responses also follow the administration of selective H1- and H2-receptor agonists. 3. 2-Methylhistamine, in doses up to 1 X 10(-7) mol/kg, lowers blood pressure by interaction with H1-receptors. Larger doses of 2-methylhistamine also lower blood pressure but this may involve H2-receptors. 4. 4-Methylhistamine, in doses up to 1 X 10(-7) mol/kg, lowers blood pressure by interaction with H2-receptors. Larger doses of 4-methylhistamine also lower blood pressure but this may involve H1-receptors. 5. 2-(2-Aminoethyl)pyridine and 2-(2-aminoethyl)thiazole both lower blood pressure by interaction with H1-receptors only. 6. The potential value and limitations of these compounds as tools to investigate the cardiovascular effects of histamine are discussed.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002415:Cats; D003864:Depression, Chemical; D005260:Female; D006632:Histamine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D008297:Male; D011725:Pyridines / Q000494:pharmacology; D011955:Receptors, Drug / Q000187:drug effects; D013329:Structure-Activity Relationship; D013844:Thiazoles / Q000494:pharmacology
D011725:Pyridines; D011955:Receptors, Drug; D013844:Thiazoles; D006632:Histamine