title: Sustained and Transient Contributions to the Rat Dark-Adapted Electroretinogram b-Wave.
abstract: The most dominant feature of the electroretinogram, the b-wave, is thought to reflect ON-bipolar cell responses. However, a number of studies suggest that the b-wave is made up of several components. We consider the composition of the rat b-wave by subtracting corneal negative components obtained using intravitreal application of pharmacological agents to remove postreceptoral responses. By analyzing the intensity-response characteristic of the PII across a range of fixed times during and after a light step, we find that the rat isolated PII has 2 components. The first has fast rise and decay characteristics with a low sensitivity to light. GABAc-mediated inhibitory pathways enhance this transient-ON component to manifest increased and deceased sensitivity to light at shorter (<160 ms) and longer times, respectively. The second component has slower temporal characteristics but is more sensitive to light. GABAc-mediated inhibition enhances this sustained-ON component but has little effect on its sensitivity to light. After stimulus offset, both transient and sustained components return to baseline, and a long latency sustained positive component becomes apparent. The light sensitivities of transient-ON and sustained-OFF components are consistent with activity arising from cone ON- and OFF-bipolar cells, whereas the sustained-ON component is likely to arise from rod bipolar cells.
authors.affiliation: Department of Optometry and Vision Sciences, University of Melbourne, 4th Floor, 162 Alice Hoy Building, Monash Road, Parkville, VIC 3010, Australia.
authors.forename: Trung M
authors.initials: TM
authors.lastname: Dang
authors.forename: Algis J
authors.initials: AJ
authors.lastname: Vingrys
authors.forename: Bang V
authors.initials: BV
authors.lastname: Bui