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M Kuze, T Akamine, H Matsubara, Y Uji, Y Uji; The Effects Of ß1-selective Adrenergic Antagonist Betaxolol On The Electroretinogram In Perfused Cat Eye . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1784.
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Purpose:To investigate the effects of the ß1-selective adrenergic antagonist betaxolol on electroretinograms (ERGs) in isolated arterially perfused cat eyes. Methods:A total of eight cat eyes were used in this study, with 17 applications of betaxolol. Experimental procedure adhered to the Association for Research in Vision and Ophthalmology on the Use of Animals in Research. In vitro arterially perfused, fully dark-adapted cat eyes, enucleated under deep anesthesia, were used to record ERGs. The eye was stimulated in the dark at 30s intervals with red flash light (620 nm, 20 ms duration, no neutral attenuation, 0.71 W/ m2 intensity on the cornea). Stimulation was adjusted using neutral density filter so that ERG b-wave amplitude lay between 150-300 µM, because the linear change of ERG b-wave amplitude is constantly obtained in proportion to the flow rate. Betaxolol was applied to the eye to reach 5.0-60.0 µM concentration. After administration of betaxolol for 10 min, 60 min was allowed for washout. Results: Betaxolol induced a dose-related increase in amplitude of a- (Pearson r =0.834, n=17, p<0.001) and b-waves (r =0.600, p<0.05). Particularly large changes were observed at 60 µM concentrations. Peak latencies of both a- and b-waves did not demonstrate major changes. Flow rate correlates with concentration of betaxolol and the most significant increase in flow rate was observed at 50 µM and 60 µM concentrations. However, no significant effect were observed at concentrations <40 µM. In most series, changes returned to control values after 40-60 min recovery periods. However we could not observe the recovery of both flow rate and ERG, which continued for at least another 90 min at concentrations ≷50µM. Conclusion:In arterially perfused cat eyes, the ß1-selective adrenergic antagonist betaxolol obviously modified retinal function under the dark adaptation by dose-dependent reversible increase in ERG a- and b-wave amplitude. These results suggest that betaxolol produces beneficial influences on ocular blood flow and retinal electrical activity in response to light. Betaxolol therefore appears to be an ideal drug for the treatment of glaucoma in which ocular circulation may play a critical role in pathogenesis. CR: None
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