An Unconventional Glutamatergic Circuit in the Retina Formed by vGluT3 Amacrine Cells

• Published in: Neuron (Cambridge, Mass.) Mass.), 2014-11, Vol.84 (4), p.708-715
• Main Authors: Lee, Seunghoon, Chen, Lujing, Chen, Minggang, Ye, Meijun, Seal, Rebecca P., Zhou, Z. Jimmy
• Format: Article
• Language: English
• Subjects: Amacrine Cells - cytology; Amacrine Cells - metabolism; Amacrine Cells - physiology; Amino Acid Transport Systems, Acidic - metabolism; Animals; Dendrites - physiology; Glutamic Acid - metabolism; Light; Mice; Neurons - cytology; Neurons - metabolism; Neurons - physiology; Retina; Retina - cytology; Retina - metabolism; Retina - physiology; Rodents; Synapses - physiology; Transmitters
• ISSN: 0896-6273; 1097-4199
• DOI: 10.1016/j.neuron.2014.10.021

In the vertebrate retina, glutamate is traditionally thought to be released only by photoreceptors and bipolar cells to transmit visual signals radially along parallel ON and OFF channels. Lateral interactions in the inner retina are mediated by amacrine cells, which are thought to be inhibitory neurons. Here, we report calcium-dependent glutamate release from vGluT3-expressing amacrine cells (GACs) in the mouse retina. GACs provide an excitatory glutamatergic input to ON-OFF and ON direction-selective ganglion cells (DSGCs) and a subpopulation of W3 ganglion cells, but not to starburst amacrine cells. GACs receive excitatory inputs from both ON and OFF channels, generate ON-OFF light responses with a medium-center, wide-surround receptive field structure, and directly regulate ganglion cell activity. The results reveal a functional glutamatergic circuit that mediates noncanonical excitatory interactions in the retina and probably plays a role in generating ON-OFF responses, crossover excitation, and lateral excitation. •vGluT3 amacrine cells (GACs) release glutamate in the retina•GACs excite direction-selective ganglion cells and a subpopulation of W3 cells•GACs have an ON-OFF receptive field center with a strong inhibitory surround•GACs likely play a role in ON-OFF responses and crossover and lateral excitation Photoreceptor and bipolar cells transmit excitation, and amacrine cells transmit inhibition in the retina. In this issue of Neuron, Lee et al. (2014) show that vGluT3 amacrine cells release glutamate and form a novel excitatory pathway.