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Takafumi Yoshioka, Taiji Nagaoka, Akitoshi Yoshida; Effect of Nitric Oxide on Increased Retinal Blood Flow in Response to Flicker Stimuli in Cats. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4666.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the role of nitric oxide (NO) in the increase in retinal blood flow (RBF) during flicker stimuli.
Twelve adult cats were used in this study. After anesthesia was induced with sevoflurane in each animal, laser Doppler velocimetry (LDV) was used to measure the vessel diameter (D) and blood velocity (V) simultaneously and calculate the RBF in the second-order retinal arterioles during flicker stimulation. In the first series of studies, the flicker frequencies and light intensities ranged from 2 to 64 Hz and 300 to 3000 lux, respectively. The durations of dark adaptation and flicker stimulation ranged from 0 to 30 minutes and 60 to 300 seconds, respectively. In the second series of studies, we injected phosphate-buffered saline (PBS) or NG-nitro-L-arginine-methyl ester (L-NAME) into the vitreous and measured the D, V, and RBF during flicker stimuli 2 hours later.
Flicker stimulations from 2 to 32 Hz increased the RBF in the retinal arterioles. In contrast, flicker stimulation with 64 Hz did not affect the RBF. At 16 Hz, the increase in RBF was enhanced in response to light intensities of 300~3,000 lux, dark adaptation times of 0~30 minutes, and flicker stimulation times of 60~180 seconds. At 16 Hz, 3,000 lux, 30 minutes of dark adaptation, and 180 seconds of stimulation time, flicker stimulation resulted in a 51% increase in RBF over baseline in the PBS group (n=6) and an 11% increase in the L-NAME group (n=6), a difference that was significant (P<0.0001).
We confirmed that the LDV system allows evaluation of the flicker-induced increase in RBF in the retinal arteries in anesthetized cats. Our results suggested that NO plays an important role in the increase in RBF during flicker stimuli.
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