Functional antagonism between calcium-antagonists and noradrenaline on isolated guinea-pig atria.
In the isolated electrically driven guinea-pig atrium the influence of D 600 and nifedipine on the action of noradrenaline was investigated. 1. The calcium-antagonists caused a dose-dependent negative inotropic effect. 10(-7) M of D 600 or nifedipine inhibited the contractile amplitude by 75 and 55%, respectively. 2. In spite of the pronounced negative inotropic effect evoked by the two calcium-antagonists, the maximal response to noradrenaline was not changed. The sensitivity of the myocardium to noradrenaline was only slightly diminished i.e. by a factor of 4.6 and 3 as calculated from the pD2-values. 3. The functional antagonism between noradrenaline and calcium-antagonists, therefore, offers the possibility to overcome cardiac side-effects of calcium-antagonists.
D000818:Animals; D016275:Atrial Function; D002118:Calcium / Q000037:antagonists & inhibitors*; D003864:Depression, Chemical; D004558:Electric Stimulation; D005711:Gallopamil / Q000494:pharmacology; D006168:Guinea Pigs; D006325:Heart Atria / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology*; D009638:Norepinephrine / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology*; D014700:Verapamil / Q000031:analogs & derivatives*
D011725:Pyridines; D005711:Gallopamil; D014700:Verapamil; D009543:Nifedipine; D002118:Calcium; D009638:Norepinephrine