The c-wave of the direct-current-recorded electroretinogram and the standing potential of the albino rabbit eye in response to repeated series of light stimuli of different intensities

In 10 experiments on five albino rabbits, the direct-current electroretinogram and the standing potential of the eye were recorded in response to repeated light stimuli (duration, 10 s; interval, 70 s), presented in four series, each consisting of 25 light flashes. Light intensities were, in order of presentation to the eyes, 3, 2, 1 and 0 log rel units (series I, II, III and IV, respectively) below the maximum output of the system. Thirty minutes of dark adaptation preceded each series. At the end of series I, the mean amplitudes of the b- and c-waves were higher and that of the a-wave relatively unchanged compared with the corresponding initial amplitudes. During series II–IV, there was a marked decrease in mean a- and b-wave amplitudes between the first and the following electroretinogram responses, and at the end of the three series, the amplitudes were still significantly reduced compared with the corresponding initial values. The mean c-wave amplitude was also markedly decreased immediately after the first electroretinogram recording, but it later recovered to a large extent. A peak in the c-wave amplitude was discerned about 14–18 minutes after the start of the recordings. A standing potential minimum during the second light stimulus was followed by a peak after about 10–13 minutes. The partially parallel behavior of the c-wave and the standing potential suggests the operation of a pigment epithelial mechanism behind the recovery of the c-wave amplitude. The final amplitudes of the b- and c-waves, and to a large extent also of the a-wave, were about the same irrespective of stimulus intensity. The adaptational processes in the rabbit appear to be more complicated than was previously thought. When electroretinogram amplitudes and standing potential levels are discussed and when one experiment is compared with another one, it is important that adaptational and stimulus conditions, as well as time course, are well controlled and clearly specified.