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Published on: December 10, 2014
Diurnal variation of cerebral blood flow in healthy humans under normal entrained conditions
Hanqi Xing1, Yang Song2, Xiaowei Wu1
1Department of Radiology, The First Affiliated Hospital of Soochow University, Suzhou, China.
Insights
Cerebral blood flow shows daily regional variations, with parietal cortex flow increasing at night while frontal and cerebellar flow decreases. Nitric oxide and neurogenic regulation may drive these changes.
Area of Science:
- Neuroscience
- Cardiovascular Physiology
- Medical Imaging
Background:
- Circadian rhythms influence physiological processes, including cerebral blood flow.
- Daily variations in cerebral blood flow may impact cerebrovascular events.
- Mechanisms underlying diurnal cerebral blood flow changes are not fully understood.
Purpose of the Study:
- To investigate diurnal variations in cerebral blood flow in healthy individuals.
- To explore potential mechanisms influencing these regional cerebral blood flow changes.
- To correlate cerebral blood flow patterns with physiological markers of vascular tone.
Main Methods:
- Arterial spin labelling MRI was used to measure relative cerebral blood flow at six time points over 24 hours.
- Resting heart rate, blood pressure, and specific blood biomarkers (e.g., nitric oxide) were collected.
- Participants included 18 healthy adults aged 22-39 years.
Main Results:
- Parietal cortical relative cerebral blood flow increased from 21:00 to 05:00, while frontal and cerebellar flow decreased.
- Negative correlation observed between parietal flow and heart rate; positive correlation between cerebellar flow and heart rate.
- Changes in parietal flow correlated with nitric oxide levels; mean arterial pressure correlated with whole-brain flow.
Conclusions:
- Regional cerebral blood flow exhibits distinct diurnal patterns, with opposing trends in parietal versus frontal/cerebellar regions.
- Diurnal variations in nitric oxide and neurogenic regulation are potential mechanisms for regional cerebral blood flow changes.
- Understanding these diurnal patterns is crucial for comprehending cerebrovascular health and event occurrence.
Abstract:
The presence of a circadian cycle of cerebral blood flow may have implications for the occurrence of daily variations in cerebrovascular events in humans, but how cerebral blood flow varies throughout the day and its mechanism are still unclear. The study aimed to explore the diurnal variation of cerebral blood flow in healthy humans and its possible mechanisms. Arterial spin labelling images were collected at six time-points (09:00 hours, 13:00 hours, 17:00 hours, 21:00 hours, 01:00 hours, 05:00 hours) from 18 healthy participants (22-39 years old; eight females) to analyse diurnal variations in cerebral blood flow. Resting heart rate and blood pressure at six time-points and blood indicators (20-hydroxyeicosatetraenoic acid, epoxyeicosatrienoic acids, prostaglandin E2, noradrenaline and nitric oxide) related to cerebral vascular tone at two time-points (09:00 hours and 21:00 hours) were collected to analyse possible influences on diurnal variations in cerebral blood flow. From 21:00 hours to 05:00 hours, parietal cortical relative cerebral blood flow tended to increase, while frontal cortical and cerebellar relative cerebral blood flow tended to decrease. There was a time-dependent negative correlation between parietal cortical relative cerebral blood flow and resting heart rate, whereas there was a time-dependent positive correlation between cerebellar relative cerebral blood flow and resting heart rate. The change of parietal cortical relative cerebral blood flow was positively correlated with the change of nitric oxide. There was also a time-dependent positive correlation between mean arterial pressure and mean whole-brain cerebral blood flow. The findings indicated that parietal cortical relative cerebral blood flow and frontal cortical/cerebellar relative cerebral blood flow showed roughly opposite trends throughout the day. The diurnal variations in relative cerebral blood flow were regional-specific. Diurnal variation of nitric oxide and neurogenic regulation may be potential mechanisms for diurnal variation in regional relative cerebral blood flow.
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