Comparison of the inhibitory effects of nifedipine and nimodipine on mechanical responses of isolated rat coronary small arteries.
The effect of nifedipine and nimodipine was studied on the spontaneous myogenic tone and on the serotonin-, potassium-, and calcium-induced contractile responses in coronary resistance arteries from 2-year-old male Wistar rats. Both drugs depressed completely and concentration-dependently the spontaneous myogenic tone. At the highest concentration, nifedipine and nimodipine reduced the serotonin and potassium responses to an average of 19% and 6% of control response. The drugs had an equipotent inhibitory effect on the serotonin response. Nimodipine, however, was more potent than nifedipine, inhibiting the potassium response. In vessels maximally activated by serotonin and potassium, both drugs concentration-dependently inhibited the calcium concentration-response curves. Nifedipine and nimodipine had an equieffective and equipotent inhibitory effect on the calcium responses in serotonin-activated vessels. Nimodipine was more potent than nifedipine, inhibiting the calcium response of potassium-activated vessels. In the highest concentration, nimodipine was also more effective than nifedipine (p less than 0.01) in inhibiting the calcium response. In conclusion, both nifedipine and nimodipine are potent and effective vasodilators, having similar actions on the spontaneous myogenic tone and serotonin-induced responses in the rat coronary resistance arteries, but nimodipine is more potent and more effective than nifedipine in inhibiting potassium-induced responses.
D000818:Animals; D001158:Arteries; D001696:Biomechanical Phenomena; D002118:Calcium / Q000037:antagonists & inhibitors / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008297:Male; D009543:Nifedipine / Q000494:pharmacology*; D009553:Nimodipine / Q000494:pharmacology*; D011188:Potassium / Q000037:antagonists & inhibitors / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D014655:Vascular Resistance / Q000187:drug effects
D012702:Serotonin Antagonists; D012701:Serotonin; D009553:Nimodipine; D009543:Nifedipine; D011188:Potassium; D002118:Calcium