Cerebrovascular effects produced by electrical stimulation of fastigial nucleus.

We used the microsphere technique and laser flowmetry to assess cerebral blood flow in 43 anesthetized rats. Cerebral blood flow did not increase significantly when the fastigial nucleus was stimulated 15 min after administration of alpha-chloralose. In animals that received maintenance doses of alpha-chloralose, the modest (50%) increase in cerebral blood flow that did occur returned toward control during stimulation despite a continued stable elevation of arterial pressure. Stimulation of fastigial nucleus 2 h after alpha-chloralose elicited a 20 +/- 3 mmHg increase in arterial pressure; cerebral blood flow increased gradually for 30-60 s after the rise in arterial pressure and reached a peak that was approximately 90% (P less than 0.05) above baseline. The stimuli did not significantly reduce vascular resistance or impair autoregulation. We did not stimulate the fastigial nucleus for more than 2 h after administration of alpha-chloralose because anesthesia was effective for only 2 h. This study demonstrates that stimulation of the fastigial nucleus in rat produces a delayed increase in cerebral blood flow that is blocked by alpha-chloralose anesthesia. The delay in increases of cerebral blood flow suggests that a metabolic mechanism, not a direct neurogenic vascular effect, may account for increases in flow with fastigial stimulation.