A relatively simple differential screening test for GABA or glycine antagonists using rat electroretinography

Intravitreal injection of GABA- and glycine-antagonists had specific and reversible effects on the ERG of rats. For example, picrotoxin induced characteristic rhythmic potentials. The effect was common to other GABA-antagonists, such as bicuculline, N-methylbicuculline and penicillin G. Strychnine caused the appearance of a- and c-like waves in response to low intensity flash stimuli in addition to the suppression of the b-wave commonly seen with agents such as asparate following higher intensity flash stimuli. The strychnine-like effect was common to other glycine-antagonist tested, such as brucine, morphine and laudanosine. The quanternization of the glycine-antagonists abolished the strychnine-like activity and endowed the ability to induce the rhythmic potentials characteristic of GABA-antagonists. This relatively simple method of observing either rhythmic potentials or a negative deflection (a-like wave) to a low intensity stimulus (about 1.0 log unit above dark threshold) in the ERG should be useful for the rapid screening of the predicted and new GABA--and glycine-antagonists.