Cardiovascular effect of nifedipine in morphine dependent rats: hemodynamic, histopathological, and biochemical evidence.

Aim: To investigate whether administration of nifedipine has considerable therapeutic effect in morphine-dependent rats.

Methods: Sixty animals were randomized into control, morphine, morphine plus nifedipine, and morphine plus dimethyl sulfoxide (DMSO, as nifedipine soluble) groups. Each group consisted of two subgroups, with and without heart injury. The groups were treated with incremental doses of morphine or morphine plus nifedipine daily for 7 days. Myocardial injury was induced by isoproterenol (50 mg/kg i.p.) on the day 7. On the day 8, the heart rate (HR), blood pressure (BP), rate-pressure product (RPP), and the plasma level of cardiac troponin I were measured and the hearts were histopathologically examined.

Results: In morphine-dependent rats, nifedipine administration was associated with a significantly higher decrease in the plasma level of cardiac troponin I than the administration of morphine alone. This finding was also significant in dependent animals that received only DMSO. HR, BP, RPP, and histopathological indices did not show significant changes in the presence of nifedipine.

Conclusion: Administration of nifedipine failed to show a significant therapeutic effect in morphine-dependent rats, especially in the group with myocardial injury.