Comparison of the alpha-adrenergic agonists, phenylephrine and methoxamine in rabbit papillary muscles
Siegl, P.K.; McNeill, J.H.
Research Communications in Chemical Pathology and Pharmacology 30(2): 221-231
1980
ISSN/ISBN: 0034-5164 PMID: 6255520 Document Number: 160716
The positive inotropic effects of the alpha-adrenergic agonists, phenylephrine and methoxamine were compared in isolated rabbit papillary muscles. Phenylephrine in the presence of 10(-7)M propranolol produced a greater response than methoxamine. Antagonism by phentolamine was competitive for phenylephrine and apparently, noncompetitive for methoxamine. Based upon observed maximum following frequencies, 10(-4)M methoxamine had a greater cardiac depressant effect than 10(-4) phenylephrine. It was suggested that phenylephrine with a beta-adrenergic antagonist possessed advantages over methoxamine as an agonist for studying cardiac alpha-adrenergic receptors in rabbit papillary muscles.