Adaptive response of brain tissue oxygenation to environmental hypoxia in non-sedated, non-anesthetized arctic ground squirrels

Ma, Yilong; Wu, S. Vincent; Rasley, Brian T.; Duffy, Lawrence K.

doi:10.1016/j.cbpa.2009.06.016

Cited by 7 publications

(19 citation statements)

References 47 publications

(61 reference statements)

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“…This study confirms, in unanesthetized animals, the observation that Pto 2 will drop significantly with an acute decline in inspired Po 2 Ma et al, 2009). In mammals, a decline in Fio 2 of 50% would be similar in the reduction of oxygen delivery to that which occurs with ascent to approximately 1/2 atm pressure at an elevation of approximately 6000 m, depending on latitude.…”

Section: Pto 2 In Brain During Normoxia and Acute Hypoxiasupporting

confidence: 86%

“…As such, it is important to understand the mechanisms that regulate oxygen delivery and establish oxygen levels in the brain. Under acute conditions, it is known that oxygen content is not held constant, because acute reduction in the partial pressure of arterial oxygen (Pao 2 ) or cerebral blood flow (CBF) will cause a reduction in Pto 2 (Leniger-Follert et al, 1975;Hoffman et al, 1996;Nwaigwe et al, 2000;Ma et al, 2009). Increased energy demand in the brain also results in increases in Pto 2 (Leniger-Follert et al, 1975), probably owing to a disproportionate increase in flow relative to metabolic rate (Kim et al, 1999).…”

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confidence: 99%

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Cerebral Oxygenation in Awake Rats during Acclimation and Deacclimation to Hypoxia: AnIn VivoElectron Paramagnetic Resonance Study

Dunn

Khan

Hou

et al. 2011

High Altitude Medicine & Biology

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Cerebral oxygenation in awake rats during acclimation and deacclimation to hypoxia: an in vivo EPR study. High Alt. Med. Biol. 12:71-77, 2011.-Exposure to high altitude or hypobaric hypoxia results in a series of metabolic, physiologic, and genetic changes that serve to acclimate the brain to hypoxia. Tissue Po 2 (Pto 2 ) is a sensitive index of the balance between oxygen delivery and utilization and can be considered to represent the summation of such factors as cerebral blood flow, capillary density, hematocrit, arterial Po 2 , and metabolic rate. As such, it can be used as a marker of the extent of acclimation. We developed a method using electron paramagnetic resonance (EPR) to measure Pto 2 in unanesthetized subjects with a chronically implanted sensor. EPR was used to measure rat cortical tissue Pto 2 in awake rats during acute hypoxia and over a time course of acclimation and deacclimation to hypobaric hypoxia. This was done to simulate the effects on brain Pto 2 of traveling to altitude for a limited period. Acute reduction of inspired O 2 to 10% caused a decline from 26.7 AE 2.2 to 13.0 AE 1.5 mmHg (mean AE SD). Addition of 10% CO 2 to animals breathing 10% O 2 returned Pto 2 to values measured while breathing 21% O 2, indicating that hypercapnia can reverse the effects of acute hypoxia. Pto 2 in animals acclimated to 10% O 2 was similar to that measured preacclimation when breathing 21% O 2 . Using a novel, individualized statistical model, it was shown that the T 1/2 of the Pto 2 response during exposure to chronic hypoxia was approximately 2 days. This indicates a capacity for rapid adaptation to hypoxia. When subjects were returned to normoxia, there was a transient hyperoxygenation, followed by a return to lower values with a T 1/2 of deacclimation of 1.5 to 3 days. These data indicate that exposure to hypoxia results in significant improvements in steady-state oxygenation for a given inspired O 2 and that both acclimation and deacclimation can occur within days.

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Section: Pto 2 In Brain During Normoxia and Acute Hypoxiasupporting

confidence: 86%

mentioning

confidence: 99%

Cerebral Oxygenation in Awake Rats during Acclimation and Deacclimation to Hypoxia: AnIn VivoElectron Paramagnetic Resonance Study

Dunn

Khan

Hou

et al. 2011

High Altitude Medicine & Biology

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“…This difference in V O2 during hyperoxia was not caused by body mass scaling as discussed in our previous study (Ma et al, 2009), where we found that V O2 during 8% O 2 exposure was significantly lower in euthermic AGS than in rats.…”

Section: Hyperoxic Response and Metabolic Rate For Osupporting

confidence: 83%

“…P t O 2 returns to the normal level after hypoxic exposure ends and ambient air inhalation resumes, indicating that AGS brain tolerates hypoxic conditions (Ma et al, 2009). When both euthermic AGS and rats are exposed to 100% O 2 inhalation, sO 2 in rats is not affected by 100% O 2 inhalation; however, sO 2 is significantly increased in AGS blood, but remains at a lower level than in rats (Ma et al, 2005).…”

Section: Introductionmentioning

confidence: 90%

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Effects of Hyperoxia on Brain Tissue Oxygen Tension in Non-Sedated, Non- Anesthetized Arctic Ground Squirrels: An Animal Model of Hyperoxic Stress

Ma¹

2011

American Journal of Animal and Veterinary Sciences

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Arctic Ground Squirrels (AGS) are classic hibernators known for their tolerance to hypoxia. AGS have been studied as a model of hypoxia with potential as a medical research model. Problem statement: Their unique resistance to the stressors of low oxygen led us to hypothesize that AGS might also be adaptable to hyperoxia. Approach: This study examined the physiological pattern associated with hyperoxia in response to brain tissue oxygen partial pressure (P t O 2 ), brain temperature (T brain ), global oxygen consumption (V O2 ) and respiratory frequency (f R ) using non-sedated and nonanesthetized Arctic Ground Squirrels (AGS) and rats. Results: We found that 1) 100% inspired oxygen (F i O 2 ) increased the baseline values of brain P t O 2 significantly in both summer euthermic AGS (24.4 ± 3.6-87.3 ± 3.6 mmHg, n=6) and in rats (18.2 ± 5.2-73.3 ± 5.2 mmHg, n = 3); P t O 2 was significantly higher in AGS than in rats during hyperoxic exposure; 2) hyperoxic exposure had no effect on brain temperature in either AGS or rats, with the brain temperatures maintaining constancy before, during and after 100% O 2 exposure; 3) systemic metabolic rates increased significantly during hyperoxic exposure in both euthermic AGS and rats; moreover, V O2 were significantly lower in AGS than in rats during hyperoxic exposure; 4) the respiratory rates for rats were maintained before, during and after 100% O 2 exposure, while the respiratory responding patterns to hyperoxic exposure changed after exposure in AGS. AGS f R was significantly lower after hyperoxic exposure than before the exposure. Conclusion: These results suggest that hyperoxic ventilation induced P t O 2 and V O2 differences between AGS and rats and led to altered respiratory patterns between these species. AGS and the rat serves as an excellent comparative model for hypoxic and hyperoxic stress studies of the brain.

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Common tenrecs (Tenrec ecaudatus) reduce oxygen consumption in hypoxia and in hypercapnia without concordant changes to body temperature or heart rate

Silva Rubio,

Kim,

Milsom

et al. 2024

J Comp Physiol B

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Adaptive response of brain tissue oxygenation to environmental hypoxia in non-sedated, non-anesthetized arctic ground squirrels

Cited by 7 publications

References 47 publications

Cerebral Oxygenation in Awake Rats during Acclimation and Deacclimation to Hypoxia: AnIn VivoElectron Paramagnetic Resonance Study

Cerebral Oxygenation in Awake Rats during Acclimation and Deacclimation to Hypoxia: AnIn VivoElectron Paramagnetic Resonance Study

Effects of Hyperoxia on Brain Tissue Oxygen Tension in Non-Sedated, Non- Anesthetized Arctic Ground Squirrels: An Animal Model of Hyperoxic Stress

Common tenrecs (Tenrec ecaudatus) reduce oxygen consumption in hypoxia and in hypercapnia without concordant changes to body temperature or heart rate

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