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AJP - Regulatory, Integrative and Comparative Physiology, Vol 268, Issue 2 454-R467, Copyright © 1995 by American Physiological Society
ARTICLES |
E. V. Golanov and D. J. Reis
Department of Neurology and Neuroscience, Cornell University Medical College, New York, New York 10021.
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.
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E. V. Golanov, J. R. C. Christensen, and D. J. Reis Neurons of a Limited Subthalamic Area Mediate Elevations in Cortical Cerebral Blood Flow Evoked by Hypoxia and Excitation of Neurons of the Rostral Ventrolateral Medulla J. Neurosci., June 1, 2001; 21(11): 4032 - 4041. [Abstract] [Full Text] [PDF] |
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