In mammals, environmental light signals are captured by the eye’s photoreceptors: rods, cones and intrinsically photosensitive melanopsin retinal ganglion cells (ipRGCs). During the last few years, ipRGCs were extensively studied and their membrane properties, projections and physiological role in regulation of circadian rhythms and pupillary light refl ex were documented. However, these studies do not explain how activity of ipRGCs affects physiology of target cells in suprachiasmatic nuclei (SCN), intergeniculate leafl et (IGL) or olivary pretectal nucleus (OPN). Some of the neurons constituting above mentioned structures, express slow oscillatory activities that are modulated by light and depend on functional input from the retina. This implicates, that mechanism of expression of slow oscillation may include synaptic drive from ipRGCs. Recently, 2-aminoethoxydiphenylborane (2-APB) was described as an acute inhibitor of ipRGCs activity. This study combines intravitreous injections of 2-APB with extracellular recordings from oscillatory OPN neurons in urethane anesthetized Wistar rat. The experiments showed that inactivation of ipRGCs activity abolish oscillatory pattern and reduce fi ring rate of OPN neurons. Injection of comparable volume of physiological saline in control experiments had no effect on oscillatory activity. To our knowledge, this is the fi rst study that directly links extraretinal neuronal fi ring with activity of ipRGCs.
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