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P.D. Gamlin, V.C. Smith, D.M. Dacey, J. Pokorny, D.H. McDougal; Melanopsin–containing Retinal Ganglion Cells Drive the Pupillary Light Reflex in the Primate . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2262.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: In primates, we have previously shown that intrinsically– photoreceptive retinal ganglion cells project to the pretectal olivary nucleus (Gamlin et al, ARVO 2001; Dacey et al., 2003), which mediates the pupillary light reflex. We therefore sought to determine the influence of these retinal ganglion cells on the primate pupillary light reflex. Methods: In one rhesus monkey, we recorded pupillary responses evoked by 10 sec pulses of light at 10 wavelengths between 430 nm and 610 nm over a 3 log unit range. Such responses were recorded under normal conditions and during blockade of ON and OFF retinal channels following an intravitreal injection of 50 µl of a cocktail of 100 mM L–AP4 and 2 mM CNQX. Prior to the injection, the animal was anesthetized with 4–5% isoflurane. To confirm injection efficacy, the flash ERG was assessed using an Espion system (Diagnosys) equipped with a ColorBurst hand–held mini–Ganzfeld simulator. Results: Following intravitreal injection of L–AP4/CNQX, the b–wave of the ERG was effectively eliminated. Nevertheless, substantial light–evoked pupillary responses were observed with monochromatic light between 430 nm and 530 nm. These responses were more sluggish than normal, and closely matched the kinetics of the light–evoked intrinsic responses seen in melanopsin–containing retinal ganglion cells in vitro (Dacey et al., ARVO 2003; Smith et al., ARVO 2003). The spectral responsivity data for these light–evoked pupillary responses were well fit by a Vitamin A1 pigment nomogram with a λmax of 488 nm. Conclusions: Intrinsic phototransduction in macaque melanopsin–containing ganglion cells contributes significantly to light–evoked pupillary responses over much of the photopic range. Under these conditions, light–evoked pupillary responses reflect a significant contribution from both conventional and intrinsic photoreceptive mechanisms.
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