Further studies of the chemical sensitivity of the oscillatory potentials of the electroretinogram (ERG) I. GABA- and glycine antagonists.

The oscillatory potentials (OPs) of the mudpuppy ERG were studied to evaluate the effects of GABA and glycine antagonists. Upon exposing the retina to bicuculline and picrotoxin, blocking agents of the putative inhibitory neurotransmitter GABA, all the OPs were selectively abolished. The earlier OPs (01-03) appeared more sensitive to the drug than the latter ones (04-05). There was no appreciable effect on the range of sensitivity and saturation level of the b-wave. Low concentrations of strychnine, blocking the effect of the putative inhibitory neurotransmitter glycine, produced a selective decrease of the amplitude of the OPs. The first (01) appeared less sensitive to the drug than the later ones. Higher concentrations extinguished all the OPs but also decreased the suprathreshold amplitude of the b-wave. In conclusion, the present results in agreement with previous work, suggest that the OPs appear to have a different origin from the b-wave and seem to be generated by inhibitory feed-back circuits within retina. The differential sensitivity of the individual oscillatory peaks indicate that perhaps chemically different synaptic activities might underlie the individual oscillatory potentials.