Effects of sodium pentobarbital on the components of electroretinogram in the isolated rat retina

Photovoltages, the fast P3(t) component of electroretinogram (ERG), were registered between two microelectrodes across the rod outer segments. The P2(t) component, obtained by subtracting the ERGs measured before the application of 50 microM APB from those measured after the application of 50 microM APB, was used as an indicator of depolarizing bipolar cell activity. Measurements of the scotopic threshold response (STR) and the oscillatory potentials (OPs) were used as indicators of third order neuron activity. The slow P3*(t) component, obtained by subtracting the photovoltages from the transretinal recording in the APB-treated retina was used as an indicator of Müller cell activity. The components of the ERG obtained in normal superfusate medium were compared with those obtained in the presence of 100 microM sodium pentobarbital. We found that sodium pentobarbital slowed the kinetics of the P2(t) component and increased its latency. The fast P3(t) component was not affected by pentobarbital. The slow P3*(t) component was slightly reduced in the presence of pentobarbital. The minor components of the ERG, the STR and the OPs, were strongly suppressed by pentobarbital. These results suggest that in rat retina pentobarbital does not affect photoreceptors, but it does affect bipolar cells and Müller cells, and it suppresses activity of third order neurons.