Titre : | Hypercapnia impairs vasoreactivity to changes in blood pressure and intraocular pressure in rat retina |
Type de document : | article de périodique |
Auteurs : | Guodong Liu ; Grant Cull ; Wang Lin ; Bang Bui |
Année de publication : | 2019 |
Langues : | Français (fre) |
Descripteurs (mots clés) : | [Thésaurus Mesh]Hypercapnie [Thésaurus Mesh]Pression artérielle [Thésaurus Mesh]Rétine [Thésaurus HELB]:Optique:pression intraoculaire
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Résumé : | SIGNIFICANCE The balance between oxygen and carbon dioxide sets the resting tone (or diameter) of retinal blood vessels. Eyes that are hypercapnic use up their “vasodilatory reserve” and therefore fail to respond adequately to changes in intraocular or blood pressure.
PURPOSE Retinal vessels are regulated by both myogenic and metabolic mechanisms. We considered whether alteration of metabolic status would modify the vascular response to ocular perfusion pressure (OPP) lowering in rat retina.
METHODS In pentobarbital anesthetized adult Brown-Norway rats, normocapnia or hypercapnia was achieved by artificially ventilating animals with air or 5% carbon dioxide in ~30% oxygen, respectively. Ocular perfusion pressure was gradually reduced to ~20 mmHg by either lowering blood pressure (slowly drawing blood from a femoral artery/vein) or manometrically increasing intraocular pressure under normocapnic or hypercapnic conditions. In all four groups (n = 7 eyes for each), a confocal scanning laser ophthalmoscope was used to acquire image sequences centered on the optic nerve throughout pressure modification. The diameter of arterioles and venules at various OPP levels was measured and expressed as percentage relative to their own baseline. The response of arterioles and venules to OPP lowering was compared between normocapnic and hypercapnic groups.
RESULTS Average arterial carbon dioxide partial pressures were 36.9 ± 2.6 mmHg in normocapnic and 64.1 ± 5.9 mmHg in hypercapnic (P < .001) animals. In the normocapnic groups, blood pressure lowering and intraocular pressure elevation resulted in significant vasodilation of both arterioles and venules (P < .0001). In the hypercapnic groups, OPP lowering–induced vasodilation was significantly attenuated compared with the corresponding normocapnic groups (P < .0001 for both, two-way analysis of variance).
CONCLUSION Hypercapnia significantly modified myogenic vascular autoregulation in response to OPP reduction. |
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