Abstract
To investigate the dynamics of tissue oxygen demand and supply during brain functions, we simultaneously recorded PO2 and local cerebral blood flow (LCBF) with an oxygen microelectrode and laser Doppler flowmetry, respectively, in rat somatosensory cortex. Electrical hind-limb stimuli were applied for 1, 2, and 5 s to vary the duration of evoked cerebral metabolic rate of oxygen (CMRO2). The electrical stimulation induced a robust increase in PO2 (4-9 Torr at peak) after an increase in LCBF (14-26% at peak). A consistent lag of ∼1.2 s (0.6-2.3 s for individual animals) in the PO2 relative to LCBF was found, irrespective of stimulus length. It is argued that the lag in PO2 was predominantly caused by the time required for oxygen to diffuse through tissue. During brain functions, the supply of fresh oxygen further lagged because of the latency of LCBF onset (∼0.4 s). The results indicate that the tissue oxygen supports excess demand until the arrival of fresh oxygen. However, a large drop in PO2 was not observed, indicating that the evoked neural activity demands little extra oxygen or that the time course of excess demand is as slow as the increase in supply. Thus the dynamics of PO2 during brain functions predominantly depend on the time course of LCBF. Possible factors influencing the lag between demand and supply are discussed, including vascular spacing, reactivity of the vessels, and diffusivity of oxygen.
| Original language | English |
|---|---|
| Pages (from-to) | 1352-1358 |
| Number of pages | 7 |
| Journal | Journal of Applied Physiology |
| Volume | 103 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - 2007 Oct |
| Externally published | Yes |
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Keywords
- Brain tissue oxygen tension
- Cerebral blood flow
- Functional brain imaging
- Oxygen transport
ASJC Scopus subject areas
- Physiology
- Endocrinology
- Orthopedics and Sports Medicine
- Physical Therapy, Sports Therapy and Rehabilitation
Cite this
Apparent diffusion time of oxygen from blood to tissue in rat cerebral cortex : Implication for tissue oxygen dynamics during brain functions. / Masamoto, Kazuto; Kershaw, Jeff; Ureshi, Masakatsu; Takizawa, Naosada; Kobayashi, Hirosuke; Tanishita, Kazuo; Kanno, Iwao.
In: Journal of Applied Physiology, Vol. 103, No. 4, 10.2007, p. 1352-1358.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Apparent diffusion time of oxygen from blood to tissue in rat cerebral cortex
T2 - Implication for tissue oxygen dynamics during brain functions
AU - Masamoto, Kazuto
AU - Kershaw, Jeff
AU - Ureshi, Masakatsu
AU - Takizawa, Naosada
AU - Kobayashi, Hirosuke
AU - Tanishita, Kazuo
AU - Kanno, Iwao
PY - 2007/10
Y1 - 2007/10
N2 - To investigate the dynamics of tissue oxygen demand and supply during brain functions, we simultaneously recorded PO2 and local cerebral blood flow (LCBF) with an oxygen microelectrode and laser Doppler flowmetry, respectively, in rat somatosensory cortex. Electrical hind-limb stimuli were applied for 1, 2, and 5 s to vary the duration of evoked cerebral metabolic rate of oxygen (CMRO2). The electrical stimulation induced a robust increase in PO2 (4-9 Torr at peak) after an increase in LCBF (14-26% at peak). A consistent lag of ∼1.2 s (0.6-2.3 s for individual animals) in the PO2 relative to LCBF was found, irrespective of stimulus length. It is argued that the lag in PO2 was predominantly caused by the time required for oxygen to diffuse through tissue. During brain functions, the supply of fresh oxygen further lagged because of the latency of LCBF onset (∼0.4 s). The results indicate that the tissue oxygen supports excess demand until the arrival of fresh oxygen. However, a large drop in PO2 was not observed, indicating that the evoked neural activity demands little extra oxygen or that the time course of excess demand is as slow as the increase in supply. Thus the dynamics of PO2 during brain functions predominantly depend on the time course of LCBF. Possible factors influencing the lag between demand and supply are discussed, including vascular spacing, reactivity of the vessels, and diffusivity of oxygen.
AB - To investigate the dynamics of tissue oxygen demand and supply during brain functions, we simultaneously recorded PO2 and local cerebral blood flow (LCBF) with an oxygen microelectrode and laser Doppler flowmetry, respectively, in rat somatosensory cortex. Electrical hind-limb stimuli were applied for 1, 2, and 5 s to vary the duration of evoked cerebral metabolic rate of oxygen (CMRO2). The electrical stimulation induced a robust increase in PO2 (4-9 Torr at peak) after an increase in LCBF (14-26% at peak). A consistent lag of ∼1.2 s (0.6-2.3 s for individual animals) in the PO2 relative to LCBF was found, irrespective of stimulus length. It is argued that the lag in PO2 was predominantly caused by the time required for oxygen to diffuse through tissue. During brain functions, the supply of fresh oxygen further lagged because of the latency of LCBF onset (∼0.4 s). The results indicate that the tissue oxygen supports excess demand until the arrival of fresh oxygen. However, a large drop in PO2 was not observed, indicating that the evoked neural activity demands little extra oxygen or that the time course of excess demand is as slow as the increase in supply. Thus the dynamics of PO2 during brain functions predominantly depend on the time course of LCBF. Possible factors influencing the lag between demand and supply are discussed, including vascular spacing, reactivity of the vessels, and diffusivity of oxygen.
KW - Brain tissue oxygen tension
KW - Cerebral blood flow
KW - Functional brain imaging
KW - Oxygen transport
UR - http://www.scopus.com/inward/record.url?scp=35348998393&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=35348998393&partnerID=8YFLogxK
U2 - 10.1152/japplphysiol.01433.2006
DO - 10.1152/japplphysiol.01433.2006
M3 - Article
C2 - 17626829
AN - SCOPUS:35348998393
VL - 103
SP - 1352
EP - 1358
JO - Journal of Applied Physiology Respiratory Environmental and Exercise Physiology
JF - Journal of Applied Physiology Respiratory Environmental and Exercise Physiology
SN - 8750-7587
IS - 4
ER -