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W Goto, H Oku, T Okuno, T Sugiyama, T Ikeda; Effects Of Topical Application Of Bunazosin Hydrochloride On Visual Evoked Potential After Intravenous Injection Of A Nitric Oxide Synthase Inhibitor In conscious Rabbits . Invest. Ophthalmol. Vis. Sci. 2002;43(13):307.
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Purpose: To investigate the effects of topical administration of bunazosin hydrochloride, an alpha-adrenoceptor inhibitor, on the impairment of the ocular circulation caused by intravenous injection of a nitric oxide synthase (NOS) inhibitor. Methods: To induce impairment of the ocular circulation in albino rabbits, we injected NG-nitro-L-arginine methyl ester (L-NAME) intravenously. The functional alterations caused by L-NAME were assessed by inspection of the visual evoked potential (VEP). Blood flow in the optic nerve head (ONH) was evaluated using a laser-speckle tissue-circulation analyzer as a normalized blur (NB) value (a quantitative index of blood velocity). Intraocular pressure (IOP) and systemic blood pressure were also measured. Bunazosin hydrochloride (0.01%) was topically administered twice (one hour and just before injection of L-NAME). Modulation by bunazosin hydrochloride of the L-NAME-induced changes in VEPs and ONH blood flow were investigated over a 2-hour period. Results: Intravenous injection of L-NAME (0, 10, 50 mg/kg) reduced VEP amplitude and ONH blood flow in a dose-dependent manner, the maximum effects [seen 60 min after intravenous L-NAME (50 mg/kg)] reducing the level to 68.7±5.4% and 50.3±2.9% of baseline, respectively. Topical administration of 0.01% bunazosin hydrochloride suppressed the reduction in VEP amplitude and preserved ONH blood flow for the entire monitoring period of 2 hours after intravenous injection of L-NAME, the levels of significance being P=0.004 and 0.001, respectively (repeated-measures ANOVA). Bunazosin hydrochloride reduced IOP, but it did not decrease perfusion pressure to the eye significantly (compared to the L-NAME-injected control group). Conclusion: These results suggested that topically applied bunazosin hydrochloride improved the impaired VEP by increasing the ocular circulation. Thus, bunazosin hydrochloride, which is used as an ocular hypotensive drug in Japan, may also be useful for the treatment of ischemic disorders of the retina and optic nerve.
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