Local cerebral blood flow (1CBF) was measured with [14C]iodoantipyrine in conscious, unrestrained rats during electrical stimulation of the fastigial nucleus (FN). Electrode position in the FN was determined by 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 s off) with currents of 30-100 μA after recovery from anesthesia produced stereotypic behavior but little effect on MABP and 1CBF. In seven other conscious rats currents could be raised to 75-200 μA without inducing seizures, resulting in sustained MABP elevations during the 1CBF measurement and significantly increased 1CBF in the sensory-motor (+45%), parietal (+31%), and frontal cortices (+56%) and the caudate-putamen (+27%) above control values (n = 9). Glucose utilization, measured with [14C]deoxyglucose, in rats similarly stimulated was significantly increased in six structures, including some of the above, indicating increases in 1CBF due to metabolic activation. Unilateral or bilateral electrolytic lesions of the FN, placed 6-7 days before 1CBF measurement, had negligible effects on resting 1CBF and on autoregulation in conscious rats. These results fail to support a specific role for the FN in physiological regulation of cerebral blood flow in unanesthetized rats.
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