TIME-COURSE OF ACTION OF AMLODIPINE AND FELODIPINE IN THE RAT IS MOSTRAPID IN SMALL ARTERIES

The time course of action of amlodipine was compared to that of felodi pine in rat mesenteric resistance arteries and aorta. Both amlodipine and felodipine caused a concentration-dependent relaxation of K+-depol arized resistance arteries: with amlodipine 3 x 10(-8) M and felodipin e 10(-9) M, complete relaxation was reached after 40 min and 10 min, r espectively. Furthermore, in resistance arteries, the time course of a ction of both drugs was shortest in vessels with the smallest diameter . In aorta, both drugs caused a marked relaxation of K+-induced tone, without reaching a maximal effect within 2 h. Recovery of K+-induced t one after both drugs was complete in resistance arteries, but not aort a, within 2 h. In resistance arteries exposed to K+ depolarization or noradrenaline, both drugs displayed the characteristics of 1,4-dihydro pyridine Ca2+ channel antagonists. The results show that amlodipine wa s slower to have an effect than felodipine, but that both drugs acted fastest in the smallest arteries.