EN
INTRODUCTION: The retina is specialized to detect and process light information by three types of cells: rods, cones, and melanopsin cells. In rodents, S‑cones are maximally sensitive to 359 nm light, thus enabling them to see and use light in the UV range. The olivary pretectal nucleus (OPN) receives strong retinal innervation and is responsible for pupillary light reflex (PLR), which depends mostly on melanopsin cell activity. AIM(S): The aim of this study was to verify whether neurons within the OPN respond to monochromatic light stimuli in the UV range. METHOD(S): The experiments were carried out on 4 adult Long Evans rats under urethane anesthesia subjected to in vivo multi‑unit extracellular recordings. The contralateral eye was stimulated by high-irradiance white light pulses and monochromatic light in the 340– 490 nm range (3 s, 10 nm interval). RESULTS: The stable activity of 43 neurons was recorded within the OPN borders and majority of them (84%) were classified as sensitive to white and monochromatic light stimuli in the UV range. OPN neurons mostly responded in a sustained manner (tonic excitation), even to short wavelength light. Moreover, they were the most sensitive to 380 nm wavelength of light from the UV range. CONCLUSIONS: The current study shows that light in the UV range widely actives OPN cells. In contrast to retinal studies, the majority of OPN neurons demonstrated sustainability and preferability towards 380 nm wavelength of light. These results suggest that S‑cones may contribute to non‑image forming functions, such as PLR. FINANCIAL SUPPORT: Supported by: 2013/08/W/ N23/00700.