Pattern ERG in rats following section of the optic nerve.

The aim of this study is to investigate in the rat the properties of the pattern electroretinogram (ERG) and to assess whether it depends upon the functional integrity of ganglion cells. Flash and pattern ERG were recorded from urethane anaesthetized hooded rats. The pattern ERG was evoked by phase alternating gratings of various spatial frequencies and contrasts. In the first part of the study we determined how the amplitude of the main harmonic of the pattern ERG (2nd harmonic) varies as a function of stimulus parameters such as spatial and temporal frequency, contrast and mean luminance. In the second part of the study we investigated the effects of the retrograde degeneration of ganglion cells following optic nerve section on the amplitude of pattern ERG. We found that the section of the optic nerve leads to the progressive disappearance of the P-ERG which is almost complete 4 months after surgery. By this time only few axotomized ganglion cells are left. The flash ERG remained unaffected. Thus, the pattern electroretinogram seems to be a simple and sensitive tool to investigate the functional integrity of retinal ganglion cells in rats.