a1 Universitaets-Augenklinik Abt. II, Forschungsstelle fuer Experimentelle Ophthalmologic, Ob dem Himmelreich 9. D-7400 Tuebingen, Germany
a2 Digital Equipment GmbH, D-8000 Muenchen 81, Germany
We studied rod function in the chicken by recording corneal electroretinograms (ERGs). The following experiments were performed to demonstrate rod function during daytime: (1) determining the dark-adaptation function; (2) measuring the spectral sensitivity by a a–b-wave amplitude criterion in response to monochromatic flickering light of different frequencies ranging from 6.5–40.8 Hz (duty cycle 1: I); (3) analyzing the response vs. log stimulus intensity (V–log I) function in order to reveal a possible two phase process; and (4) determining the spectral sensitivity function either in a non-dark adapted state or after dark adaptation of the animals for I and 24 h. None of these experiments demonstrated clear evidence of rod function during daytime. On the other hand, we found rods histologically by light- and electron microscopy. Therefore, we repeated our ERG recordings during the night (between midnight and 3:00 A.M.). Without previous dark adaptation, rod function could be seen immediately in the same experiments described above. The result shows that, in the chicken, rods are turned on endogenously during the night but are scarcely functional during the day.
(Received November 16 1990)
(Accepted February 11 1991)
Reprint requests to: Frank Schaeffel, Universitaets-Augenklinik Abt. II, Forschungsstelle fuer Experimentelle Ophtalmologie, Ob dem Himmelreich 9, D-7400 Tuebingen, Germany.