The Effect of Barbiturate on Retinal Functions. II. Effects on the c‐wave of the Electroretinogram and the Standing Potential of the Sheep Eye

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Abstract
The present work is the second in a series of investigations on the effect of barbiturate on retinal functions. The changes in the c‐wave of the conventional ERG and in the standing potential (SP) of the intact sheep eye were studied after i.v. administration of an ultra‐short‐acting barbiturate, thiopental. The c‐wave was transiently decreased or abolished after a small dose (< 10 mg/kg), whereas a negative shift could be observed in the SP. Larger doses resulted in negative‐positive cyclic variations of the c‐wave amplitude and the SP resembling damped oscillations. There was an increase of the a‐ and b‐waves after barbiturate administration, not related to the SP‐changes. The effect of barbiturate on the components of the conventional ERG and the SP was also studied after selective blocking of the function of the pigment epithelial cells with sodium iodate. Hereby, the barbiturate induced changes of the c‐wave and the SP disappeared, whereas those of the a‐ and b‐waves remained. On the basis of these results, the possibility that barbiturate has a dual site of action on the retina, namely on the neuroretina and on the pigment epithelial cells, cannot be excluded.