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S. Hetu, G. Cordahi, R. Couture, E. Vaucher; Assessment of Retinal/Choroidal Blood Flow Using Laser Doppler Flowmetry (LDF) in Rats. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5031.
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Laser Doppler Flowmetry (LDF) is a non-invasive technique commonly used to assess retinal and choroidal blood flow in humans. This study aimed at testing the usefulness of this technique for the assessment of retinal blood flow in rats under hypercapnia and after pharmacological interventions. The relative contribution of the choroid circulation in the LDF signal was determined after retinal arteries occlusion by photocoagulation.
Male Wistar rats (200-250g) were anesthetised with urethane (1.2 mg/kg, i.p.), placed in a stereotaxic apparatus and their pupils dilated (atropine 1%). In these conditions, no ocular movements were observed. The LDF probe (Moors Instruments, 1 emitting fibre, 8 collecting fibres) was placed in contact with the cornea, parallel with the optic axis. Blood pressure and heart rate were monitored continuously and hematologic parameters were measured. Hypercapnia was induced by inhalation of CO2 (8 % in medical air) while adenosine (2µM), sodium nitroprusside (10 µM) and endothelin-1 (1µg/mL) were injected intravitreally (5 µL). The cornea was maintained humid with topical application of saline throughout the experiment.
Blood flow was significantly increased by hypercapnia (19%), adenosine (14%) and sodium nitroprusside (16%), yet decreased by endothelin-1 (11%). Photocoagulation of retinal arteries decreased by 33% from baseline blood flow values (P<0.001).
Results show that LDF represents a suitable non-invasive technique to monitor online quantitative changes of retinal blood flow in response to pharmacological stimuli in vivo. This technique could be used to assess vasoreactivity of retinal vessels in ocular diseases.
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