Polygraphycal studies were carried out in order to evaluate the effects of
Diltiazem (Ca-antagonist) on cerebral circulation in cats. In addition to these studies, the inhibitory effect of
Diltiazem on incubated blood-, and
serotonin-induced vasocontraction of basilar arteries was observed through on operating microscope. Experimental vasospasm were induced by local administration of incubated blood and 10(-5)--10(-6) M
serotonin solution. The required dose of
Diltiazem, 30-300 micrograms/kg, was injected by one shot intravenously. CBF slightly decreased concomitantly with transiently decreased blood pressure shortly after
intravenous injection of
Diltiazem. After that, CBF increased for 15-20 minutes and returned to the state similar to that before the administration of
Diltiazem. The changes in reactive pattern of CBF depend on the doses of
Diltiazem and related to changes of CAR and VAR which were thought to indicate the blood of cardiac output. Vasocontraction induced by incubated blood and
serotonin was released 30-35 per cent for 30 minutes after
intravenous injection of
Diltiazem 100 micrograms/kg. However, by administration of
Diltiazem before and after local application of incubated blood and
serotonin on basilar arteries, vasocontraction was inhibited completely. These data suggest that administration of
Diltiazem (Ca-antagonist) might be useful in the prophylaxis and treatment of vasospasm following
rupture of
cerebral aneurysm.