OPN3 (aka. panopsin or enkephalopsin) belongs to the families of extraretinal opsins having putative role of CNS tissue photosensitivity. OPN3 mRNA has earlier been localized in rodent brain, but actual protein and its location has not been clarified. In this study, we aimed to define OPN3 protein localization and abundance in rodent brain and the site of cellular locality.The distribution and localization of OPN3 protein in mouse brain and peripheral tissues was assessed by immunohistochemical staining using rabbit polyclonal antibody to OPN3. OPN3 protein content was measured using western plotting and SDS-PAGE. Altogether nine mice were sacrified and their tissues prepared. Samples were cut in to sections and fluerescent dye labeled antibody was used to stain before confocal laser scanning microscopy. The specificity of labeling and immununoreaction was secured by primary antibody omitting and immunizing peptide blocking experiment.

Results: 

We found OPN3 protein abundant in mouse brain, but not in periphery or in negative controls. Neuronal OPN3 was present in granular pattern intracellularly in mouse paraventricular area, cerebral cortex and cerebellar Purkinje cells. In Purkinje cells also dendrites were strongly immunopositive. Immunoreaction took place mostly in neuronal soma, but not in nuclei.

Conlusion: 

Previously in mRNA-level assessed OPN3 encoding results in abundant presence of OPN3 protein in neurons of mouse brain, but not in non-neuronal peripheral tissues.