Dihydropyridine calcium channel blockers are not uniform in terms of their 
action on calcium channel. L-type calcium channel blockers dilate the resistance 
arterioles. Cilnidipine is a dihydropyridine calcium channel blocker that also 
acts on N-type calcium channels, and may dilate venules through its effect on 
the sympathetic receptor. The influence of an L-type calcium channel blocker 
(nifedipine) or this L+N type blocker at 10(-7) mol to 10(-4) mol on venular 
diameter was examined by superfusion of male Syrian hamster cheek pouches. 
Nifedipine dose dependently dilated the arterioles alone, whereas cilnidipine 
dilated both arterioles and venules. Application of 10(-7) mol omega conotoxin, 
an inhibitor of N-type channels, after nifedipine led to significant dilation of 
venules, while it had no influence when administered after cilnidipine. These 
findings indicate that the effects of calcium channel blockers on the venules 
differ according to the action on N-type calcium channels, and that cilnidipine 
(an L+N type calcium channel blocker) dilates venules through its additional 
action on N-type channels.