(2008-11-17) Grimes, William Norman; Walker, Robert; Chemical Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The mammalian retina is capable of signaling over a vast range of mean light levels (~10^10). Such a large dynamic range is achieved by segregating signals into contrasting pathways and utilizing excitatory and inhibitory neural circuits. The goal of this study was to elucidate subcellular mechanisms responsible for shaping dendritic computation and reciprocal inhibition within the retinal circuitry.
Amacrine cells make up a unique class of inhibitory interneurons which lack anatomically distinct input and output structures. Although these interneurons clearly play important roles in complex visual processing, there is relatively little known about the ~30 subtypes. A17 amacrine cells have been shown to shape the time course of visual signaling in vivo. Intuition might suggest that a wide field (~400 µm) interneuron, such as A17, would provide long range lateral inhibition or center surround inhibition. However, using multi-disciplinary approaches, we have uncovered multiple mechanisms which underlie dendritic integration and synaptic transmission in A17 that allow it to respond with a high degree of synapse specificity. Additionally, these mechanisms work in concert with post-synaptic mechanisms to extend the dynamic range of reciprocal inhibition in the inner retina.