Drug Screening by In-Vitro Recording of Multisite ERGs
Guenther E., Herrmann T., Zrenner E., Stett A.
Natural and Medical Science Institute, University of Tuebingen, Reutlingen
Purpose: A retina sensor, based on multisite recording of local ERGs in vitro has been developed to easily and effectively assess effects of pharmacological compounds on retinal activity.
Method: Intact retinas from one day old chicken were dissected and cut into small pieces. The samples were placed with the ganglion side down on the translucent surface of a microelectrode array (MEA) with 60 planar, substrate-integrated electrodes (diameter 30 µm, electrode spacing 200 µm). Experiments were started afer a 30 min. recovery period under stationary perfusion with oxygenated and temperature controlled (35°C ringer solution. Under these conditions, measurements could be performed for up to 4 hours. Full-field light stimulation (duration 500 ms, 1 Hz) was given at different contrast levels and wavelenght.
Results: Light stimulation resulted in the parallel recording of 60 local electroretinograms (microERGs) at a filter setting of 0.5 Hz-2.8 kHz. Offline filtering with a highpass filter (200 Hz) allowed extraction of ganglion cell action potentials. Bath application of the sodium channel blocker TTX resulted in a complete loss of ganglion cell activity. Application of AP4 (10 µM), a compound known to block signal transmission from photoreceptors to ON bipolar cells resulted in a loss of the b-wave. After washing b-wave amplitude was restored to control le
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