[The effect of a calcium channel blockade on the reactivity of the cerebral vessels in rabbits].

The changes of cerebrovascular reactivity (CVR) under influence of calcium antagonist nimodipine (0.01 and 0.06 mg/kg i.v.) and verapamil (0.6 and 1.0 mg/kg i.v.) were investigated in chronic experiments in 12 rabbits. Platinum electrodes were implanted into cortex, thalamus and hypothalamus, and cerebral blood flow was measured in these zones by H2-clearance method. CVR was evaluated as a ratio: cerebral blood flow after 7% CO2 inhalation to initial level. This ratio, or reactivity coefficient (RC), in normal conditions is 1.49-1.59. Nimodipine in dose 0.01 mg/kg resulted in significant decrease (by 15-20%) of RC only in cortex. In dose 0.06 mg/kg this decreased RC was about 20-30% in cortex and in hypothalamus, but in thalamus the changes of RC were insignificant. Verapamil in dose 0.6 mg/kg resulted in different changes of RC: increase in cortex, decrease in thalamus, but in hypothalamus no changes. In dose 1.0 mg/kg RC was decreased in cortex by 15-20%, in other zones were no changes.