Positive inotropic but no relaxant effects of phenylephrine in cat papillary muscle.
J Cyclic Nucleotide Res, 1978/8;4(4):291-8.
Meinertz T, Schmelzle B, Scholz H
PMID: 214466
Abstract
The effect of phenylephrine (30 micron) in the presence of propranolol (1 micron) on electrically induced isometric twitches and on KCl-contractures was studied in papillary muscles from reserpine-pretreated cats at 25 degrees C. Under these conditions phenylephrine has previously been shown to act solely via alpha-adrenoceptors and not to increase c-AMP. Phenylephrine increased force of contraction, time to peak tension and relaxation time. Contracture tension remained unaffected. These data indicate that the stimulation of cardiac alpha-adrenoceptors, in contrast to beta-adrenergic stimulation, does not lead to so-called relaxant effects. This qualitative difference between the two responses is probably due to the different capacity of both stimuli to increase c-AMP.
MeSH terms
Animals; Cats; Cyclic AMP; Electric Stimulation; In Vitro Techniques; Myocardial Contraction; Myocardium; Papillary Muscles; Phenylephrine; Potassium Chloride; Propranolol
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