Effect of dihydropyridine derivatives on beating rate and contractile force of guinea pig isolated atria

Calcium channel blockers such as nifedipine possess a dramatic role in treatment of various cardiovascular diseases including angina pectoris, cardiac arrhythmias, and hypertension, so study of cardiovascular effects of derivatives of these drugs seems necessary. The aim of the present study was to evaluate the effects of synthesized dihydropyridine derivatives on chronotropic and inotropic responses of guinea pig isolated atria in comparison with nifedipine.
Thirty-two male guinea pigs were divided to four equal groups, randomly. After induction of anesthesia, the atria were isolated and attached to physiograph. Three synthesized dihydropyridine derivatives and nifedipine were incubated into organ bath in concentrations 10-9 to 10-3 M, accumulatively and their effects on atrial beating rate and contractile force were evaluated.
The inhibitory effects of all of these derivatives in concentrations of 10-5 to 10-3 M on atrial beating rate were more potent than nifedipine (p≤0.001), while their effects in reducing the atrial contractile force in concentrations of 10-8 to 10-3 M were weaker than nifedipine (p≤0.001).
Considering the stronger effects of these derivatives in reducing the atrial beating rate and the weaker effects of these compounds in diminution of the atrial contractile force compared with nifedipine, these derivatives may possess obvious antianginal properties with minimum effects on cardiac contractility.