The pupillary light reflex induced by red and blue light stimulations, and melanopsin photoreception of the rabbit.

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Recently, a new photosensitive pigment, melanopsin, was found in 1998. Later, melanopsin-containing retinal ganglion cells (mRGCs) were discovered and revealed that mRGCs would depolarize without input from the photoreceptors, meaning that these cells were photosensitive. The mRGCs mediate the pupillary light reflex. We investigated the mechanisms of photoreception by retinal photoreceptor cells, and to evaluate the relative contribution of pupil light response using the control, pharmacological blockade of neurotransmission (PB) model and a transgenic model of retinal degeneration (Tg) rabbit. Although rod and cone photoreceptors were disappeared in the PB and Tg model, miosis was still induced during exposure to blue light (470nm). Our study also indicated that some histologically-identified RGCs were consistent with the characteristics and structures of mRGC. The greater sustained constriction of pupils to blue light in eyes with outer retinal damage reflects mRGC activation.