ROLE OF THE CEREBELLAR FASTIGIAL NUCLEUS IN THE PHYSIOLOGICAL REGULATION OF CEREBRAL BLOOD-FLOW

Local cerebral blood flow (ICBF) was measured with [C-14]iodoantipyrin e in conscious, unrestrained rats during electrical stimulation of the fastigial nucleus (FN). Electrode position in the FN was determined b y blood pressure (MABP) responses to stimulation under anesthesia. In nine rats in which MABP responses had been variable under anesthesia, bipolar stimulation (50 Hz, 0.5 ms, 1 s on/1 a off) with currents of 3 0-100 mu A after recovery from anesthesia produced stereotypic behavio r but little effect on MABP and ICBF. In seven other conscious rats cu rrents could be raised to 75-200 mu A without inducing seizures, resul ting in sustained MABP elevations during the ICBF measurement and sign ificantly increased ICBF in the sensory-motor (+45%), parietal (+31%), and frontal cortices (+56%) and the caudate-putamen (+27%) above cont rol values (n = 9). Glucose utilization, measured with [C-14]deoxygluc ose, in rats similarly stimulated was significantly increased in six s tructures, including some of the above, indicating increases in ICBF d ue to metabolic activation. Unilateral or bilateral electrolytic lesio ns of the FN, placed 6-7 days before ICBF measurement, had negligible effects on resting ICBF and on autoregulation in conscious rats. These results fail to support a specific role for the FN in physiological r egulation of cerebral blood flow in unanesthetized rats.