GABAC receptor-mediated inhibition in the retina

Inhibition at bipolar cell axon terminals regulates excitatory signaling to ganglion cells and is mediated, in part, by GABA(C) receptors. We investigated GABA(C) receptor-mediated inhibition using pharmacological approaches and genetically altered mice that lack GABA(C) receptors. Responses to applied GABA showed distinct time courses in various bipolar cell classes, attributable to different proportions of GABA(A) and GABA(C) receptors. The elimination of GABA(C) receptors in GABA(C) null mice reduced and shortened GABA-activated currents and light-evoked inhibitory synaptic currents (L-IPSCs) in rod bipolar cells. ERG measurements and recordings from the optic nerve showed that inner retinal function was altered in GABA(C) null mice. These data suggest that GABA(C) receptors determine the time course and extent of inhibition at bipolar cell terminals that, in turn, modulates the magnitude of excitatory transmission from bipolar cells to ganglion cells. (C) 2004 Elsevier Ltd. All rights reserved.