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Reflex-mediated reduction in human cerebral blood volume
Timothy D Wilson1, J Kevin Shoemaker, R Kozak
1Neurovascular Research Laboratory, School of Kinesiology, London, Ontario, Canada.
Summary
Sympathetic nervous system activation reduces cerebral blood volume in gray matter during simulated stress. These findings suggest active venoconstriction plays a key role in cerebrovascular responses.
Area of Science:
- Neuroscience
- Cardiovascular Physiology
- Medical Imaging
Background:
- Adrenergic nerves influence the human cerebrovasculature, but their functional role in cerebral hemodynamics is not fully understood.
- Sympathoexcitatory reflexes are critical for maintaining homeostasis during physiological stress.
Purpose of the Study:
- To investigate regional cerebrovascular responses to sympathoexcitatory reflexes.
- To evaluate changes in cerebral blood volume (CBV), mean transit time (MTT), and cerebral blood flow (CBF) during simulated stress.
Main Methods:
- Eight healthy volunteers underwent contrast-enhanced computed tomography (CT).
- Cerebrovascular parameters were measured at baseline, during lower body negative pressure (LBNP), and cold pressor test (CPT).
- Regional analysis included cortical gray matter (GM), white matter (WM), and basal ganglia/thalamus (BGT).
Main Results:
- Both LBNP and CPT significantly reduced gray matter CBV.
- CPT led to reduced MTT in gray and white matter.
- Cerebral blood flow showed only modest changes, suggesting active venoconstriction contributed to reduced CBV.
Conclusions:
- Sympathoexcitatory reflexes induce heterogeneous cerebrovascular changes, primarily reducing gray matter CBV.
- Active venoconstriction is implicated in the observed reduction of cerebral blood volume.
- These findings enhance understanding of neurogenic control of cerebral hemodynamics.