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Tomofumi Tani, Taiji Nagaoka, Seigo Nakabayashi, Kenji Sogawa, Akitoshi Yoshida; Retinal Artery Response To Decreasing Ocular Perfusion Pressure In Cats. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6035.
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To investigate whether nitric oxide (NO) regulates retinal circulation during decreases in ocular perfusion pressure (OPP) in cats.
NG-nitro-L-arginine-methyl ester (L-NAME, n=6), a NO synthase inhibitor, or phosphate-buffered saline (PBS, n=8) was injected intravitreously. The intraocular pressure (IOP) increased in stepwise increments. The vessel diameter (D) and blood velocity (V) were measured simultaneously in the first-order retinal arterioles by laser Doppler velocimetry (CLBF model 100, Canon), and the retinal blood flow (RBF) and wall shear rate (WSR) were calculated. The mean arterial blood pressure (MABP) was measured during elevated IOP. OPP was defined as MABP-IOP and the OPP decreased from 70 to 30 mmHg.
In the PBS group, we found significant increases in the D (p<0.01) despite decreases in the V (p<0.01), RBF (p<0.01), and WSR (p<0.01). However, in the L-NAME group, there were no increases in the D and significant decreases in the V (p<0.01), RBF (p<0.01), and WSR (p<0.01). There were enhanced decreases in the V, RBF, or WSR in the L-NAME group compared to the PBS group.
These results suggested that the RBF decreases in response to low OPP induced by elevated IOP and that NO may have a role in maintaining the RBF.
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