Adenosine Enhances Functional Activation of Blood Flow in Cat Optic Nerve Head during Photic Stimulation Independently from Nitric Oxide

Chorioretinal Vascular Oxygen Tension Changes in Response to Light Flicker

“…25,26 Contrary to our results, venous PO 2 measured by phosphorescence imaging was reported to increase at the optic nerve head during flicker. 7 The change in the venous PO 2 may be different because the optic nerve head veins receive blood from the retina, choroid, and the optic nerve head microvasculature and because oxygen consumption in response to flicker may differ between the retina and the optic nerve head tissues.…”

“…light flicker, inner retinal metabolic rates are increased, 1,2 which causes reductions in retinal venous PO 2 . However, the vasodilatory response to light flicker increases retinal blood flow, 8,25,28 resulting in increased retinal arterial PO 2 that counteracts the effects of increased oxygen consumption on the retinal venous PO 2 . The arteriovenous PO 2 difference may vary depending on the distance from the optic nerve head because the volume of measured tissue that is consuming oxygen changes.…”

Assessment of Retinal and Choroidal Blood Flow Changes Using Laser Doppler Flowmetry in Rats

“…6,10-12 LDF was previously used in a number of animal models notably rabbits and cats to assess choroidal blood flow [13][14][15][16] or optic nerve head blood flow. 17,18 Rodents are used to model common pathological conditions that affect ocular blood flow in humans. To date the ability to measure retinal blood flow in rodent models has relied on terminal techniques such as microspheres trapping or autoradiography.…”

Is the Real In Vivo Nitric Oxide Concentration Pico or Nano Molar? Influence of Electrode Size on Unstirred Layers and NO Consumption

“…The effects of unstirred layers influenced by fluid motion and NO consumption by electrodes have a special bearing on measurement of [NO] of in vivo arterioles perfused with blood. Is it possible that the measured [NO] near in vivo arterioles in the mid‐to‐high nM range in in vivo preparations of the retina , small intestine , skeletal muscle , cheek pouch of hamsters , and cerebral cortex , and in many more studies, is an artifact caused by flow inside the vessel causing some stir effect? In the case of an in vivo arteriole, the electrode sensor is positioned touching the outer smooth muscle layer of the vessel wall or perhaps some overlying connective tissue with blood flow on the endothelial surface.…”

“…A separate line of data on mid NM [NO] to cause vascular dilation comes from infusion studies with GSNO and nitroglycerin into human arm vessels. Quite remarkably, single digit nanomoles per minute infusion caused 50–100% increases in blood flow . However, if one calculates the plasma flow, not whole blood flow, in milliliters per minute into which the nanomoles per min infusions occurred, the effective plasma concentrations initially reached into the multiple hundreds of NM concentration.…”