Intraretinal Oxygen Distribution in the Monkey Retina and the Response to Systemic Hyperoxia

Yu, Dao‐Yi; Cringle, Stephen J.; Su, Er‐Ning

doi:10.1167/iovs.05-0694

Cited by 159 publications

(151 citation statements)

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“…13 A 60% change in systemic arterial pO 2 corresponded with a 43% change in the choroidal pO 2 measurement, similar to a previous study that measured a 49% change in choroidal pO 2 with oxygen microelectrodes. 32 In the current study, the A-V difference in the retinal circulation also increased with increasing fractions of inspired oxygen, which may be due to autoregulation. It is known that both retinal veins and arteries constrict in response to hyperoxic challenge.…”

Section: Discussionsupporting

confidence: 55%

“…When the systemic arterial pO 2 was above 100 mmHg, the choroidal pO 2 was found to be approximately one half of the systemic arterial pO 2 , in agreement with a previous study that used oxygen microelectrodes. 32 With infusion of N ω -NLA, a marked decrease in choroidal pO 2 was demonstrated, which may be attributed to inhibition of the synthesis of NO that maintains a vasodilatory influence on the choroidal vasculature. 16 Previous studies have demonstrated a decrease in choroidal blood flow with intravenously administered systemic inhibitors of NOS.…”

Section: Discussionmentioning

confidence: 96%

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A Method for Chorioretinal Oxygen Tension Measurement

Shahidi¹,

Shakoor²,

Blair³

et al. 2006

Current Eye Research

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Purpose-To report an optical imaging system that was developed to measure oxygen tension (pO 2 ) in the chorioretinal vasculatures. The feasibility of the system for the measurement of changes in pO 2 separately in the retinal and choroidal vasculatures was established in rat eyes by varying the fraction of inspired oxygen and inhibiting nitric oxide activity.Methods-Our optical section phosphorescence imaging system was modified to provide quantitative measurements of pO 2 separately in the retinal and choroidal vasculatures. A narrow laser line was projected at an angle on the retina after intravenous injection of an oxygen-sensitive probe (Pd-porphyrin), and phosphorescence emission was imaged. A frequency-domain approach allowed measurements of the phosphorescence lifetime by varying the phase relationship between the modulated excitation laser light and sensitivity of the imaging camera. Chorioretinal pO 2 was measured while varying the fraction of inspired oxygen and during intravenous infusion of N ω -nitro-L-arginine (N ω -NLA), a nonselective nitric oxide synthase inhibitor.Results-The systemic arterial pO 2 varied according to the fraction of inspired oxygen. The pO 2 in the retinal and choroidal vasculatures increased as the fraction of inspired oxygen was increased. Compared with base-line, choroidal pO 2 decreased during infusion of N ω -NLA, whereas the pO 2 in the retinal vasculatures remained relatively unchanged. The choroidal pO 2 decreased markedly with each incremental increase in N ω -NLA infusion rate, in the range 1-6 mg/min, and there was no additional change in the choroidal pO 2 at N ω -NLA infusion rates above 6 mg/min.Conclusions-An optical method combining pO 2 phosphorescence imaging with chorioretinal optical sectioning was established that can potentially be applied for better understanding of retinal and choroidal oxygen dynamics in physiologic and pathologic states.

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Section: Discussionsupporting

confidence: 55%

Section: Discussionmentioning

confidence: 96%

A Method for Chorioretinal Oxygen Tension Measurement

Shahidi¹,

Shakoor²,

Blair³

et al. 2006

Current Eye Research

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“…2) show that pO 2 in the ganglion cell layer of the ex vivo retina increases dramatically from 34 to 548 mm Hg when switching from 21% to 100% O 2 . In contrast, pO 2 in the ganglion cell layer in vivo has been reported to increase only modestly, from ∼21 mm Hg to ∼53 mm Hg, when switching from normoxic to hyperoxic conditions (15). This small increase in O 2 tension within the retina in vivo might not be sufficient to induce the modulatory changes in neurovascular coupling observed in the ex vivo retina.…”

Section: Resultsmentioning

confidence: 94%

Oxygen modulation of neurovascular coupling in the retina

Mishra

Hamid

Newman

2011

Proc. Natl. Acad. Sci. U.S.A.

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Neurovascular coupling is a process through which neuronal activity leads to local increases in blood flow in the central nervous system. In brain slices, 100% O 2 has been shown to alter neurovascular coupling, suppressing activity-dependent vasodilation. However, in vivo, hyperoxia reportedly has no effect on blood flow. Resolving these conflicting findings is important, given that hyperoxia is often used in the clinic in the treatment of both adults and neonates, and a reduction in neurovascular coupling could deprive active neurons of adequate nutrients. Here we address this issue by examining neurovascular coupling in both ex vivo and in vivo rat retina preparations. In the ex vivo retina, 100% O 2 reduced light-evoked arteriole vasodilations by 3.9-fold and increased vasoconstrictions by 2.6-fold. In vivo, however, hyperoxia had no effect on light-evoked arteriole dilations or blood velocity. Oxygen electrode measurements showed that 100% O 2 raised pO 2 in the ex vivo retina from 34 to 548 mm Hg, whereas hyperoxia has been reported to increase retinal pO 2 in vivo to only ∼53 mm Hg [Yu DY, Cringle SJ, Alder VA, Su EN (1994) Am J Physiol 267:H2498-H2507]. Replicating the hyperoxic in vivo pO 2 of 53 mm Hg in the ex vivo retina did not alter vasomotor responses, indicating that although O 2 can modulate neurovascular coupling when raised sufficiently high, the hyperoxia-induced rise in retinal pO 2 in vivo is not sufficient to produce a modulatory effect. Our findings demonstrate that hyperoxia does not alter neurovascular coupling in vivo, ensuring that active neurons receive an adequate supply of nutrients.functional hyperemia | glial cells | prostaglandins N euronal activity in the CNS induces local increases in blood flow (1, 2), a homeostatic response termed functional hyperemia. Neurovascular coupling, the process mediating this response, is thought to involve signaling from neurons to glial cells to blood vessels. Neuronal activity induces a rise in intracellular Ca 2+ in glial cell endfeet surrounding vessels, leading to the release of vasoactive arachidonic acid metabolites and resulting in vasomotor responses (2-6). Experiments in brain slices and in the ex vivo retina have revealed that glial activation can evoke both vasodilation and vasoconstriction. Evoked vasodilations are mediated by cyclooxygenase (COX) products (3, 5) and epoxyeicosatrienoic acids (EETs) (6-9), whereas vasoconstrictions are mediated by 20-hydroxyeicosatetraenoic acid (20-HETE) (4,6).A recent study demonstrated that neurovascular coupling is modulated by O 2 in brain slices (10). Both neuronal and glial cell stimulation elicited vasodilations in brain slices exposed to 20% O 2 . In contrast, vasoconstrictions were evoked in the presence of 100% O 2 . However, another recent study reported the opposite effect of O 2 in vivo (11). In that study, increasing systemic O 2 using hyperbaric hyperoxygenation had no effect on cortical functional hyperemia. Resolving these conflicting findings is critical, given that hyperoxia (breat...

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“…Electroretinography (11,12) is widely used to study retinal electrical activity and function. Oxygenation and oxygenation changes in the retina have been studied using oxygen electrodes (13,14), phosphores-cence (15), and, more recently, intrinsic optical imaging technique (16 -18). Several methods also exist for measuring blood flow in the retina, including fluorescein angiography (19,20) which can measure retinal circulation and indocyanine-green angiography (21,22) which can measure choroidal circulation in the fovea.…”

mentioning

confidence: 99%

Magnetic resonance imaging of tissue and vascular layers in the cat retina

Shen

Cheng

Pardue

et al. 2006

Magnetic Resonance Imaging

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Purpose: To report the visual resolution of multiple cell and vascular "layers" in the cat retina using MRI. Materials and Methods:T 2 -and diffusion-weighted MRI at 4.7 Tesla was performed. Layer-specific thickness, T 2 , spin density, apparent diffusion coefficient perpendicular (ADC Ќ ) and parallel (ADC ) to the retinal surface were tabulated. T 1 -weighted MRI was acquired before and after intravenous administration of Gd-DTPA and subtraction images were obtained. Histology was performed for validation.Results: Three distinct "layers" were observed. The inner strip nearest to the vitreous (exhibiting large T 2 , ADC, spin density with Gd-DTPA enhancement) overlapped the ganglion cell layer, bipolar cell layer, and the embedded retinal vascular layer. The middle strip (exhibiting small T 2 , ADC, spin density without Gd-DTPA enhancement) overlapped the photoreceptor cell layer and the inner and outer segments. The outer strip (exhibiting large T 2 , ADC, spin density with Gd-DTPA enhancement) overlapped the tapetum and choroidal vascular layer. T 2 , spin density, ADC Ќ and ADC of different "layers" were tabulated. The inner strip was slightly thicker than the other two strips. The total thickness, including neural and nonneural retina, was 358 Ϯ 13 m (N ϭ 6) by MRI and 319 Ϯ 77 m (N ϭ 5) by histology.Conclusion: MRI provides a noninvasive tool to study the retina with laminar specificity without depth limitation.

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Intraretinal Oxygen Distribution in the Monkey Retina and the Response to Systemic Hyperoxia

Cited by 159 publications

References 18 publications

A Method for Chorioretinal Oxygen Tension Measurement

A Method for Chorioretinal Oxygen Tension Measurement

Oxygen modulation of neurovascular coupling in the retina

Magnetic resonance imaging of tissue and vascular layers in the cat retina

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