The Electroencephalogram, Blood Flow, and Oxygen Uptake in Rabbit Cerebrum

Abstract

Summary: In the present study, the relationships among electroencephalo graphic (EEG) amplitude shifts, cerebral blood flow (CBF), and cerebral oxy gen uptake (CMROz) have been characterized in halothane-anesthetized rab bits. CBF was measured by timed collection of venous effluent from the supe rior sagittal sinus. CMR02 was calculated as the product of CBF and the arteriovenous difference in oxygen content. The depth of anesthesia in the first series of experiments was maintained at a constant level that was characterized by spontaneous EEG shifts from high-to low-voltage states (HV -L V shifts).These shifts were associated with transient decreases in mean arterial pressure (MAP), which averaged 23 ::+:: 2 mm Hg (n = 17). Ninety seconds after spon taneous HV-LV shifts, MAP had returned to its original value, CBF had in creased by 26 ::+:: 7% (11 = 8), and CMROz had increased 22 ::+:: 4% (n = 7). In a second series of experiments, HV-L V shifts were induced by a 90-s application of a standardized nociceptive stimulus (11 = 13). Following these stimulation induced HV-LV shifts, CBF increased 28 ::+:: 5% and CMROz increased 27 ::+:: In a variety of studies, cerebral blood flow (CBF) has increased following sustained decreases in electroencephalographic (EEG) amplitude (HV-LV

Regulation of regional cerebral blood flow by cholinergic fibers originating in the basal forebrain

“…These data suggest that at least one component of the increase in cortical CBF after cutaneous noxious stimulation of any segmental skin area is independent of changes in systemic blood pressure and of any concomitant passive vasodilation. Pearce et al (1981) showed in anesthetized rabbits that the increase in CBF induced by noxious somatic stimulation could be partially blocked by scopolamine, a muscarinic cholinergic receptor antagonist, and suggested that cholinergic mechanisms participated in cerebral vasodilation resulting from such stimulation.…”

Cerebrovascular Anatomy and Blood Flow Measurements in the Rabbit

“…The advantage of the technique is that samples of venous blood are easily obtained for analysis of content of substances, thus allowing calculations of rates of uptake and release (Pearce et al, 1981;Scremin, Sonnenschein, and Rubinstein, unpublished). Although the limits of the area of cortex drained by the sagittal sinus can only be approximated, as indicated in Figs 8-10, the weight (g) of this cortical region can be estimated by the ratio of directly measured outflow (mllmin) to flow measured in the same vessel with H2 clearance (ml g-l min-l), as indicated in Results.…”

Cerebral Vascular System

“…The slope of the regression of CBF on CGU, that defines the gain of the mechanism that adjusts blood flow to metabolic demand, is enhanced after pharmacologic inhibition of the enzymatic breakdown of ACh and decreased by the cholinergic muscarinic blocker scopolamine Scremin and Jenden 1996). Moreover, the increase in CBF observed during spontaneous cortical arousal, or somatosensory stimulation, is markedly reduced by cholinergic blockade with atropine or scopolamine, and enhanced by inhibition of acetylcholinesterase with physostigmine (Scremin et al, 1973;Pearce et al, 1981;Tsukada et al, 1997).…”