The effect of ethyl apovincaminate on vasospasm of the circulatory isolated internal carotid artery in dogs.

The vasodilator effect of ethyl apovincaminate (Cavinton) was studied upon the circulatory isolated internal carotid arteries (in dogs), which had been proved to be a typical locus of vasospasm in the cerebral arterial system. The effects of ethyl apovincaminate were studied under conditions of experimental spasm produced in the artery. The drug caused a dilator effect which was considerably greater and longer-lasting than that of theophylline. The dilatory effect of ethyl apovincaminate was the greater the higher was the initial tone of the arterial smooth muscles. Neither accumulation of the drug nor habituation of the vascular wall was observed when ethyl apovincaminate was administered repeatedly. The effects of the drug considerably decreased when Ca++ was eliminated from the arterial wall. It regularly decreased the vasoconstrictor effects of serotonin and increased K+ in the perfusion fluid and boosted the vasodilatory effect of theophylline upon the artery. On the other hand, increase of cyclic AMP in the vascular wall potentiated the effect of ethyl apovincaminate, while PGE2 decreased the latter.