[Pharmacologic sensitivity of the photopic c wave in the electroretinogram of the chicken. II. Effects of sodium iodate and general anesthesia].

Iodate poisoning is known to induce both a retinal degeneration which is restricted in a first stage to the pigment epithelium and a selective suppression of the c-wave ([5] to [10]). In the chicken we did not obtain such electrophysiological or morphological effects. In both acute (i.v. or i.m. injections, up 50 mg/kg) and chronic experiments (4 X 45 mg/kg daily) the photopic c-wave of the chicken appeared to be fairly insensitive to sodium iodate, except at high concentrations (greater than 100 mg/kg in a single injection) which proved to be highly cardiotoxic. The ultrastructure of the retinal pigment epithelium and of the photoreceptors appeared quite normal in retinas treated with the highest concentration of the drug. Sodium pentobarbital (Nembutal), ketamine (Ketalar) and ethyl-carbamate (Urethane) were used as general anesthetics. The c-wave appeared to be differentially sensitive to these drugs. The suppressant effect was strongest with Nembutal and lowest with Urethane. The selective sensitivity of the c-wave to general anesthetics may explain why it was repeatedly stated in the literature that c-waves did not exist in a number of cone dominated retinas.