The development of the rod photoresponse from dark-adapted rats.

PURPOSE: To study electroretinographic a- and b-wave responses of rats at the ages during which rod outer segment length (ROS) and rhodopsin content increase.
METHODS: Electroretinographic responses to brief, full-field stimuli were recorded from dark-adapted young (ages 12 to 30 days) and adult rats. The amplitude of the a-wave and the amplitude and implicit time of the b-wave were examined as a function of stimulus intensity. Sensitivity (S), saturated amplitude (RmP3), and delay (td) of the rod cell responses were calculated from the a-waves.
RESULTS: The developmental increase in saturated a-wave amplitude parallels, but lags behind, growth of outer segment length, whereas the saturated b-wave amplitude increases with about the same course as rhodopsin content of the retina. The sensitivity, S, depends on rhodopsin content, and the developmental decrease in the flash energy required to produce a half-maximum b-wave amplitude is inversely proportional to the developmental increase in rhodopsin content. No significant age-dependent variation in td can be detected.
CONCLUSION: During development, ROS length and rhodopsin content of the retina are significant determinants of a- and b-wave response parameters.