title: Antibodies against retinal photoreceptor-specific proteins reveal axonal projections from the photosensory pineal organ in teleosts.
abstract: With the aid of specific antisera to the retinal proteins S-antigen and alpha-transducin and to the rhodopsin apoprotein opsin, we have labeled various cell populations in the pineal organ, parapineal organ, habenular nucleus, and subcommissural organ in two teleost species: the rainbow trout and the European minnow. Although these proteins are associated with photoreceptor functions, not only photoreceptor cells but also the majority of parenchymal cells in the pineal organ were immunoreactive. Immunoreactive cells with dendrite- and axonlike processes were observed also in the parapineal organ and the habenular nucleus. Furthermore, S-antigen-immunoreactive, long, axonal processes were observed in the pineal organ and could be traced from the pineal organ to the habenular nucleus and to the pretectal area. In the light of recent HRP electron microscopical and immunocytochemical studies we propose (1) that not only the classical pineal photoreceptor cells of poikilothermic vertebrates but also other types of CSF-contacting neurons may be the phylogenetic ancestors of mammalian pinealocytes, and (2) a close interrelationship between the pineal organ and the limbic system, effectuated by the direct projections from pineal photoreceptors/CSF-contacting neurons/pinealocytes to the habenular nucleus, and by displaced "pinealocytelike" elements scattered in the habenular nucleus.
authors.affiliation: Department of Zoology, University of Lund, Sweden.
authors.forename: P
authors.initials: P
authors.lastname: Ekström
authors.forename: R G
authors.initials: RG
authors.lastname: Foster
authors.forename: H W
authors.initials: HW
authors.lastname: Korf
authors.forename: J J
authors.initials: JJ
authors.lastname: Schalken
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology*; D000941:Antigens / Q000276:immunology; D019393:Arrestin; D001369:Axons / Q000502:physiology*; D005136:Eye Proteins / Q000276:immunology* / Q000378:metabolism; D005399:Fishes / Q000502:physiology*; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000276:immunology; D010786:Photoreceptor Cells / Q000378:metabolism*; D010870:Pineal Gland / Q000502:physiology*; D012160:Retina / Q000378:metabolism; D017299:Rod Opsins; D009435:Synaptic Transmission; D015293:Transducin; D014337:Trout
chemical_list: D000906:Antibodies; D000941:Antigens; D019393:Arrestin; D005136:Eye Proteins; D008565:Membrane Proteins; D017299:Rod Opsins; D015293:Transducin