INTRODUCTION: The dorsal lateral geniculate nucleus (dLGN) of the rat thalamus is a relay structure that receives light signals from three types of retinal photoreceptors: rods, cones, and melanopsin cells. From three types of cones, only S-cones allow rodents to see light in the ultraviolet range and further use it to image and non-image forming visual functions, including classic vision during the night. AIM(S): S-cones are maximally sensitive to UV light peaking at 359 nm; however, an unanswered question is whether dLGN cells share a similar wavelength characteristic. METHOD(S): Thus, we performed in vivo extracellular multi-electrode recordings in 5 fully pigmented adult male Long Evans rats under isoflurane anaesthesia combined with monochromatic light stimulations. Animals were dark adapted for 30 min and then different light stimuli in the UV range (3 s, 490‑340 nm, 10 nm interval) were presented to the rat’s contralateral eye, while recording neuronal activity of LGN cells. RESULTS: High-irradiance light in the UV range elicited responses in 42% (n=38) of light‑sensitive neurons within the dLGN. Recorded neurons were the most sensitive to 380 nm wavelength of light and responded mostly in a transient manner in terms of the shape of evoked photoresponse. Moreover, they did not show any spatial distributions across the LGN. CONCLUSIONS: Our study confirms that light in the UV range activates the dLGN and can play an important role in image forming functions. In contrast to previous retinal studies, we found out that dLGN cells are most effectively excited by 380 nm. FINANCIAL SUPPORT: Supported by: 2013/08/W/ N23/00700.
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