The influence of alpha 1- and alpha 2-adrenoceptor agonists on cardiac output in rats and cats.
In pithed rats, but not in pithed cats, the alpha 2-/dopamine agonist B-HT 920 (10-300 micrograms kg-1) increased cardiac output. The increase was inhibited by yohimbine (1 mg kg-1), but not by sulpiride (0.3 mg kg-1) and nifedipine (1 mg kg-1). Both in pithed rats and cats, the alpha 1-adrenoceptor agonist methoxamine (30-300 micrograms kg-1 and 30-1000 micrograms kg-1, respectively) increased cardiac output. This increase (rats) was inhibited by prazosin (0.1 mg kg-1). The results indicate the existence of functional venous alpha 2-adrenoceptors in pithed rats, and their absence in pithed cats. Furthermore, alpha 2-adrenoceptor-mediated venoconstriction appears independent of extracellular calcium.
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D001381:Azepines / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects*; D002415:Cats; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013045:Species Specificity; D013469:Sulpiride / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D001381:Azepines; D015016:Yohimbine; C024763:talipexole; D013469:Sulpiride; D008729:Methoxamine; D011224:Prazosin