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Global cerebral blood flow decreases during pain
R C Coghill1, C N Sang, K F Berman
1Neurobiology and Anesthesiology Branch, National Institute of Dental Research, Bethesda, Maryland, USA.
Summary
Painful stimuli significantly decrease cerebral blood flow (CBF) by 22.8%. This study quantitatively measured CBF changes during capsaicin-induced pain, revealing a novel physiological response.
Area of Science:
- Neuroscience
- Medical Imaging
Background:
- Positron emission tomography (PET) has identified brain regions activated by pain.
- Quantitative examination of pain-induced cerebral blood flow (CBF) changes is lacking.
Purpose of the Study:
- To quantitatively assess global CBF changes during capsaicin-evoked pain.
- To characterize the physiological response of CBF to painful stimuli.
Main Methods:
- Utilized H215O intravenous bolus method with arterial blood sampling.
- Collected PET scans during rest, capsaicin pain, and innocuous vibration in 14 subjects.
Main Results:
- Painful stimulation induced a significant 22.8% decrease in global CBF from resting levels (P < 0.0005).
- This CBF reduction was independent of changes in arterial PCO2 or heart rate.
Conclusions:
- Painful stimuli elicit a previously unidentified global decrease in cerebral blood flow.
- The precise mechanism underlying this pain-induced CBF reduction requires further investigation.