The olivary pretectal nucleus (OPN), suprachiasmatic nucleus and the intergeniculate leaflet of the thalamus, play a crucial role in the entrainment of circadian rhythms. All mentioned nuclei receive input from the retina - the only source of information about environmental light in mammals. It is known that rod/cone- and melanopsin-mediated photoreception are needed to display proper responses of circadian pacemaker to light stimuli. Our previous studies described population of OPN cells which fire in an oscillatory mode with a period of about 2 min. This rhythmic firing pattern requires intact excitatory input from the retina. We have shown that blockade of contralateral rod/ cone photoreception caused a decrease in firing rate of OPN cells without influencing their rhythmic activity. However, inhibition of contralateral melanopsin photoreception showed 3 types of neuronal responses: complete disappearance (n=5), temporary disturbances (n=5) and no changes (n=2) in oscillatory pattern of OPN cells. To clarify the likelihood that persistence of oscillatory pattern in 2 of the cases is caused by ipsilateral retinal innervation, we performed in vivo experiments on Wistar rats combining electrophysiology with intraocular injections. Contralateral eye was injected with glutamatergic receptor antagonists or 2-aminoethoxydiphenylborane to inhibit rodcone or melanopsin phototransduction respectively. Tetrodotoxin was used to suppress ipsilateral retinal activity. The results have shown that simultaneous blockade of melanopsin phototransduction and ipsilateral retinal activity strongly decreased firing rate of oscillatory cells (10.63 ± 2.81 to 2.60 ± 2.19 Hz) and caused disappearance of their rhythmic spiking. Interestingly, vanishing of the rhythm was temporary in 3 out of 7 cases and recovered oscillations were longer (95.93 ± 30.11 to 128.33 ± 48.31 s). We suggest that ipsilateral retinal innervation may play a role in the oscillatory activity of some OPN cells.