The Circuitry Underlying Rod Bipolar Cell Sensitization

Abstract

Dim light vision requires the dopamine D1 receptor for the sensitization of rod bipolar cells by GABA. However, the circuit behind this mechanism is poorly defined. We used electroretinogram recordings of mice with genetic and pharmacological manipulations to investigate the identity of the cells in the circuit controlling rod bipolar cell sensitivity. We found that tonic GABA input onto rod bipolar cells comes from a wide-field amacrine cell rather than horizontal cells. The output of this wide-field amacrine cell is directly regulated by voltage-gated sodium channels and dopamine-dampened serial inhibition, providing multiple regulatory sites for adaptation in the rod system.