The effect of 2-amino-4-phosphonobutyric acid on the oscillatory potentials of the electroretinogram.

Previous reports have shown that an intravitreal injection of 2-amino-4-phosphonobutyric acid, a glutamate analogue that selectively blocks the photoreceptors' input to the on-bipolar cells, produces a rapid decrease in the amplitude of the electroretinographic b-wave. To our knowledge, the effect of this glutamate analogue has not been examined on the oscillatory potentials. We therefore conducted such a study. A needle electrode was inserted into the anterior chamber of the eyes of seven anesthetized and paralyzed rabbits to record simultaneously the electroretinogram and the oscillatory potentials. These responses were evoked by flashes of white light delivered in mesopic conditions. As expected, an injection of 2-amino-4-phosphonobutyric acid, produced a rapid decrease in the amplitude of the b-wave, while the a-wave was relatively spared. The amplitude of the oscillatory potentials also decreased rapidly. At maximal effect, the electroretinogram essentially consisted of a normal a-wave followed by small oscillations and no evidence of a b-wave. The 100-1000 Hz recording confirmed that the oscillations seen on the postinjection electroretinograms were remnants of the original oscillatory potentials.