THE EFFECTS OF ACETAZOLAMIDE ON THE ELECTRORETINOGRAPHIC RESPONSES INRATS

Purpose. To study the mechanisms and sites of action of the carbonic a nhydrase inhibitor, acetazolamide (AZM), on the rod- and cone-mediated electroretinogram (ERG) of the dark-adapted rat. Methods. After a wit hin-subjects design, ERG responses to brief, full-field flashes were r ecorded from adult (60 to 90 days old) albino rats,with and without AZ M (5 mg/100 g, intraperitoneally). Flickering stimuli (6 and 26 Hz) we re used to study rod- and cone-mediated responses. Aspartate-isolated responses of the isolated retina were recorded with and without AZM in the superfusate. The a-wave and PIII responses were fitted with a mod el of the rod's response by estimating the maximum response (Rm(P3)), sensitivity (S), and delay t(d). The b-wave response amplitude and imp licit time were examined as a function of stimulus energy. The paramet ers obtained in the AZM-treated and untreated conditions were compared . Results. Acetazolamide causes a significant decrease in saturated ro d response, b-wave amplitude, aspartate-isolated PIII, and the rod- an d cone-mediated responses to flickering light. The estimated sensitivi ty of the rod response (S), b-wave sensitivity, and b-wave implicit ti me are not altered significantly by AZM. Conclusion. Acetazolamide, pr obably through mechanisms that acidify the retina, attenuates the ampl itudes of the retinal responses without significant effect on sensitiv ity.