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B.T. Reed, K.T. Keyser, F.R. Amthor; Requirement for 7-LIKE nAChRS in the Cholinergic Pathway That Mediates Motion Detection in the Retina . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4143.
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Purpose: Acetylcholine (ACh) contributes to the response properties of many ganglion cells in the rabbit retina, including those that are directionally selective (DS) (Ariel and Daw, 1982a,b). For example, the cholinergic pathway is necessary for DS responses to drifting gratings (Grzywacz et al., 1998). We tested whether DS ganglion cells respond to other complex stimuli such as transparent and second order motion (SOM). In primate cortex, for example, Snowden et al. (1991) showed that DS cells in V1 but not MT, respond vigorously to transparent motion. We tested whether DS ganglion cells responded to these complex stimuli, whether ACh contributed to those responses, and which receptor subtype, if any, mediated the Ach component of the responses. Methods: We recorded extracellularly from rabbit retinal ganglion cells in everted eyecup preparations during visual stimulation. The visual stimulus was generated using a VGA computer monitor driven by a Windows machine running custom software. Our transparent motion stimulus was two transparent screens of dots moving over each other in opposite directions. Our SOM stimulus was a checkerboard-like pattern of squares in which each column of checks sequentially alternated in contrast but not luminance to simulate motion across the board. An α7-nAChR-specific antagonist (i.e. MLA) was added to the superfusate during visual stimulation. Results: Transparent motion evoked DS responses that were eliminated by nanomolar concentrations of MLA. In contrast to the directional responses to transparent motion, we found that DS retinal ganglion cells did not respond selectively to the SOM stimuli we used. Conclusions: In this study, we demonstrated that retinal DS ganglion cells respond to and appear to code for transparent motion but not SOM. Our data suggests a role for α7 nAChRs in mediating DS responses to transparent motion.
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