LAUSR

OFF-type bipolar cells (OFF-BCs) are interneurons connecting cone and retinal ganglion cells in the retina. In the mammalian retina, the cone signals are received by alpha-amino3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate-type ionotropic glutamate receptors (iGluRs) in OFF-BCs. The bipolar cells in the retina respond to continuous variations in light with a graded potential in an analogue manner. It is unclear what role the kinetics of the iGluRs play in the temporal coding and synaptic transmission from the cones to the OFFBCs. In this study, we analyzed the role of the kinetics of AMPA receptors (AMPARs) in transmitting visual information to the OFF-BCs by a computer simulation using developed mathematical models. We showed that the AMPARs modulated the frequency characteristics, which strongly depend on the baseline glutamate level. Our results also demonstrated that the response of OFF-BCs to the square-wave pulse of glutamate was similar to that of the ON-OFF type when the baseline glutamate level is around 0.5 mM, which enhanced temporal contrasts. The results suggest that the function would improve the sensitivities of the spatiotemporal contrast in collaboration with the local eye movement. This modeling study of retinal neurons would lead to the improvement and development of more effective stimulation for devices of retinal prostheses.