Effects of nicardipine on collar-induced intimal thickening and vascular reactivity in the rabbit

The effects of nicardipine treatment on collar-induced intimal thickening a nd on accompanying reactivity changes in rabbit carotid artery have been in vestigated. Treatment for three weeks with subcutaneous nicardipine (20 mg kg(-1) per d ay) significantly inhibited the intimal thickening caused by perivascular a pplication of a silicone rubber collar. Potassium chloride (KCl), phenyleph rine and 5-hydroxytryptamine (5-HT) induced concentration-dependent contrac tions in both sham-operated and collared arteries. Collar-induced attenuati on of maximum KCl-, phenylephrine- and 5-HT-induced contraction was not aff ected by nicardipine. Collaring caused the means of pot values (the negativ e logarithm of EC50 values, 50% effective concentration) of 5-HT and phenyl ephrine to increase and decrease, respectively. Nicardipine did not affect the altered sensitivity to these agonists. Neither collar implantation nor nicardipine treatment altered the pD(2) values for acetylcholine- and nitro glycerine-induced relaxations. These results demonstrate that nicardipine inhibits collar-induced intimal thickening in rabbit carotid artery without affecting the accompanying chan ges in vascular reactivity, indicating a possible lack of association betwe en the development of intimal thickening and altered reactivity.