Pial arterial vasodilation by intravenous nimodipine in cats

In a series of animal experiments, isopropyl (2-methoxyethyl)-1,4-dihydro-2,6-dimethyl-4(3-nitrophenyl)-3,5-pyridinedicarboxylate (nimodipine) was administered by infusion to 10 anesthetized cats. Reaction of the pial arteries was studied through a cranial window, using a multichannel video angiometer setup. With a dose of 0.0005 mg kg-1 min-1, the arteries, having a mean diameter at rest of 80 micrometers, showed a dilation by 3.96%, while a dose of 0.001 mg kg-1 min-1 resulted in a dilation by 24.59%. At the same time, blood pressure decreased by less than 10%. Further increase of dosage led to additional marked dilation but also to a drop in blood pressure by almost 30%. The effect of dilation lasted for more than 20 min after termination of infusion.