Blockade by burimamide of the effects of clonidine on cardiac contractility phosphorylase activation and cyclic adenosine monophosphate in isolated guinea pig heart.
Clonidine in a dose-range of 2.5 microgram to 80 microgram caused positive inotropic effect, which was accompanied by increase in the cyclic AMP levels and phosphorylase-activation of the isolated perfused guinea pig heart. Clonidine-induced biochemical and mechanical effects were blocked by burimamide, an H2-receptor antagonist Propranolol (1 x 10(-6)M), phentolamine (1 x 10(-6)M) or reserpine pretreatment, did not affect the clonidine responses on the perfused guinea pig heart. Clonidine reduced the 4-methyl-histamine (H2-agonist) responses of guinea pig heart. Our data suggest that the cardiac effects of clonidine may be due to stimulation of H2-type of receptors.
D000818:Animals; D002049:Burimamide / Q000494:pharmacology*; D003000:Clonidine / Q000037:antagonists & inhibitors*; D000242:Cyclic AMP / Q000032:analysis*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000201:enzymology; D010762:Phosphorylase a / Q000032:analysis*; D006005:Phosphorylases / Q000032:analysis*; D011970:Receptors, Histamine H2 / Q000187:drug effects; D013268:Stimulation, Chemical; D013890:Thiourea / Q000031:analogs & derivatives*
D011970:Receptors, Histamine H2; D000242:Cyclic AMP; D010762:Phosphorylase a; D006005:Phosphorylases; D013890:Thiourea; D003000:Clonidine; D002049:Burimamide