Proposed model of the bipolar-amacrine-ganglion cell synapse in encoding intensity.

<p>Ganglion layer cells express AMPA/KARs and NMDARs in the synaptic and perisynaptic space, respectively. (A) Under control conditions inhibitory circuits regulate glutamate released by both transient and sustained bipolar cell terminals, resulting in activation of predominantly AMPA/KARs. Spike count of transient cells has a small dynamic range and high sensitivity compared to sustained cells. (B) When inhibition was blocked the dynamic range and sensitivity changed, most notably for sustained cells. (C) However, the additional suppression of NMDARs had little effect on sustained cell responses but altered transient cell responses so that they carried information similar to that of sustained cells. (D) shows the combined responses of transient and sustained cells, equally weighted, under control conditions. (E) shows the combined responses of transient and sustained cells, equally weighted, when inhibition is blocked and both NMDARs and AMPA/KARs are active.