Forskolin effects on slow inward current and phasic tension of frog atrial fibres: modulation by adenosine and phosphodiesterase inhibitors.
The effects of forskolin, which is known as a direct activator of adenylate cyclase were studied on the slow inward calcium current (Isi) and phasic tension of frog atrial fibres. Forskolin induced a dose-dependent positive inotropic effect related to an increase in the slow inward calcium current. These effects, which were not reproduced by 1,9-dideoxyforskolin, seemed to result from an activation of adenylate cyclase. The action of forskolin was antagonized by adenosine and potentiated by phosphodiesterase inhibitors with the following order of potency: rolipram greater than theophylline greater than dipyridamole; M & B 22,948 was without influence. This study suggests that adenosine and rolipram might be suitable tools for studying the implication of cAMP in the modulation of contraction in frog atrium.
Gauthier
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Laboratoire de Physiologie Générale, CNRS 290, Université de Poitiers, France.
Soustre
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D000241:Adenosine / Q000494:pharmacology*; D000818:Animals; D015220:Calcium Channels / Q000187:drug effects; D005576:Colforsin / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000242:Cyclic AMP / Q000032:analysis; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D006325:Heart Atria / Q000187:drug effects; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology; D011893:Rana esculenta; D011895:Rana ridibunda; D013268:Stimulation, Chemical
D015220:Calcium Channels; D010726:Phosphodiesterase Inhibitors; D005576:Colforsin; D011433:Propranolol; D000242:Cyclic AMP; D000241:Adenosine; C047983:1,9-dideoxyforskolin