The light response of ON bipolar neurons requires Gαo

Abstract

ON bipolar neurons in retina detect the glutamate released by rods and cones via metabotropic glutamate receptor 6 (mGluR6), whose cascade is unknown. The trimeric G-protein Go might mediate this cascade because it colocalizes with mGluR6. To test this, we studied the retina in mice negative for the α subunit of Go (Gαo-/-). Retinal layering, key cell types, synaptic structure, and mGluR6 expression were all normal, as was the a-wave of the electroretinogram, which represents the rod and cone photocurrents. However, the b-wave of the electroretinograrn, both rod- and cone-driven components, was entirely missing. Because the b-wave represents the massed response of ON bipolar cells, its loss in the Gαo null mouse establishes that the light response of the ON bipolar cell requires Go. This represents the first function to be defined in vivo for the a subunit of the most abundant G-protein of the brain.