The contribution of NMDA receptors to contrast coding in ON retinal ganglion cells of Mus musculus
Date
2024
Authors
Westby, Tamatea
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Abstract
The retina encodes contrast (the difference in light intensity between an object and its background) using a complex network of neurons that end in ganglion cells (GCs) which transmit visual signals to the brain. GCs express both AMPA and NMDA type glutamate receptors, with NMDA receptors (NMDARs) having high glutamate affinity and variable localization patterns. Previous studies in guinea pig retinas found no NMDAR contribution to contrast coding in ON-∝ GCs but found that these receptors were expressed in mice ON-GCs. My study investigated the contribution of NMDARs to contrast coding in mouse ON-GCs. I used whole-cell voltage clamp electrophysiology in ON-GCs from Mus musculus retinas and recorded light-evoked responses to spots of varying contrast. I then determined receptor-specific contributions to the recorded responses using a deconvolution technique which avoided the potential confounding effects of using pharmacology. I first investigated whether NMDARs contribute to low contrast responses and then examined how their conductance changes with increasing contrast. The results revealed a significant NMDAR component to low contrast responses that scaled with increasing contrast. These findings provide new insight into contrast coding mechanisms in the retina, suggesting that NMDARs play a key role in shaping ON-GC responses.