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Cerebral blood flow (rCBF), measured by laser-Doppler flowmetry, spontaneously fluctuates at approximately 6 events/min in the anesthetized rat. These cerebrovascular waves (CWs) are preceded by simultaneous and synchronous bursts of electrocorticographic activity similar to burst-suppression/spindle-burst electroencephalogram patterns. Identical burst-CW complexes are evoked by single electrical pulses of specific sites in the cerebellar fastigial nucleus or rostral ventrolateral medulla. These consist, sequentially, of a constant initial triphasic (positive-negative-positive) potential reversing polarity in lamina V, variable afterbursts, and transient elevations of rCBF appearing approximately 1.2 s after burst onset. Evoked bursts are occluded by spontaneous bursts appearing < 50 s earlier. Procainization of the cortex reversibly blocks burst-CW complexes. Gradually increasing stimulus frequency proportionally increases the numbers of burst-CW complexes before rCBF rises. We conclude that spontaneous and evoked burst-CW complexes result from excitation of common neurons in lamina V. These intracortical "vasodilator" neurons are spontaneously excited by thalamocortical afferents generating burst-suppression electroencephalogram (EEG) patterns and excited reflexively by afferent signals from the fastigial nucleus or rostral ventrolateral medulla and couple intrinsic neuronal activity to local vascular mechanisms generating vasodilation.
Golanov et al. (Wed,) studied this question.