THE C-WAVE OF THE DIRECT-CURRENT ELECTRORETINOGRAM AND THE STANDING POTENTIAL OF THE ALBINO RABBIT EYE IN RESPONSE TO REPEATED SERIES OF LIGHT STIMULI WITH DIFFERENT INTERSTIMULUS INTERVALS

The direct-current electroretinogram and the standing potential of the eye of seven albino rabbits were recorded in response to repeated lig ht stimuli, which were presented in four consecutive series. The inter vals between the beginning of succeeding stimuli were 8 minutes, 4 min utes, 2 minutes and 70 seconds (series 1, 2, 3 and 4, respectively). S timulus duration (10 seconds) and light intensity (6.8 x 10(4) lux) we re constant during the experiments. The series lasted for 36-40 minute s, and each was preceded by 30 minutes of dark adaptation. During seri es 1, the end amplitudes of the a-, b- and c-waves were not significan tly changed compared with the initial levels. During series 2, 3 and 4 , the a-, b- and c-wave amplitudes were markedly reduced immediately a fter the first electroretinogram recording. The a- and b-waves then re covered to a limited extent, but the c-wave was more fully restored. A slight peak in the c-wave amplitude could be discerned 16-20 minutes after the start of recording. A decrease in the standing potential was seen 50-54 seconds after the start of light stimulation during all fo ur series, and a peak occurred 12-16 minutes after the start of record ing. The similarity in behavior between the c-wave and the standing po tential suggests the operation of a pigment epithelial mechanism behin d the more complete recovery of the c-wave amplitude. When electroreti nogram amplitudes and standing potential levels are discussed, and whe n one experiment is compared with another one, it is important that ad aptational and stimulus conditions, as well as time course, are well c ontrolled and clearly specified.