title: Oxytocin expression and function in the posterior retina: a novel signaling pathway.
abstract: OBJECTIVE
  Oxytocin (OXT) is recognized as an ubiquitously acting nonapeptide hormone that is involved in processes ranging from parturition to neural development. Its effects are mediated by cell signaling that occurs as a result of oxytocin receptor (OXTR) activation. We sought to determine whether the OXT-OXTR signaling pathway is also expressed within the retina.
  
  
  METHODS
  Immunohistochemistry using cell-specific markers was used to localize OXT within the rhesus retina. Reverse transcriptase PCR and immunohistochemistry were used to assess the expression of OXTR in both human and rhesus retina. Single-cell RT-PCR and Western blot analyses were used to determine the expression of OXTR in cultured human fetal RPE (hfRPE) cells. Human fetal RPE cells loaded with FURA-2 AM were studied by ratiometric Ca(2+) imaging to assess transient mobilization of intracellular Ca(2+) ([Ca(2+)]i).
  
  
  RESULTS
  Oxytocin was expressed in the cone photoreceptor extracellular matrix of the rhesus retina. Oxytocin mRNA and protein were expressed in the human and rhesus RPE. Oxytocin mRNA and protein expression were observed in cultured hfRPE cells, and exposure of these cells to 100 nM OXT induced a transient 79 ± 1.5 nM increase of [Ca(2+)]i.
  
  
  CONCLUSIONS
  Oxytocin and OXTR are present in the posterior retina, and OXT induces an increase in hfRPE [Ca(2+)]i. These results suggest that the OXT-OXTR signaling pathway is active in the retina. We propose that OXT activation of the OXTR occurs in the posterior retina and that this may serve as a paracrine signaling pathway that contributes to communication between the cone photoreceptor and the RPE.
authors.affiliation: Division of Neonatology, Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States The Endocrinology-Reproductive Physiology Program, University of Wisconsin, Madison, Wisconsin, United States.
authors.forename: Patrick
authors.initials: P
authors.lastname: Halbach
authors.affiliation: Division of Neonatology, Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States McPherson Eye Research Institute, University of Wisconsin, Madison, Wisconsin, United States.
authors.forename: De-Ann M
authors.initials: DA
authors.lastname: Pillers
authors.affiliation: Division of Neonatology, Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States The Endocrinology-Reproductive Physiology Program, University of Wisconsin, Madison, Wisconsin, United States.
authors.forename: Nathaniel
authors.initials: N
authors.lastname: York
authors.affiliation: Division of Neonatology, Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States.
authors.forename: Matti P
authors.initials: MP
authors.lastname: Asuma
authors.affiliation: Division of Neonatology, Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States.
authors.forename: Michelle A
authors.initials: MA
authors.lastname: Chiu
authors.affiliation: Division of Neonatology, Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States.
authors.forename: Wenxiang
authors.initials: W
authors.lastname: Luo
authors.affiliation: Division of Neonatology, Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States.
authors.forename: Sara
authors.initials: S
authors.lastname: Tokarz
authors.affiliation: Division of Neonatology, Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States The Endocrinology-Reproductive Physiology Program, University of Wisconsin, Madison, Wisconsin, United States Departments of Obstetrics/Gynecology, University of Wisconsin, Madison, Wisconsin, United States.
authors.forename: Ian M
authors.initials: IM
authors.lastname: Bird
authors.affiliation: Division of Neonatology, Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, Wisconsin, United States.
authors.forename: Bikash R
authors.initials: BR
authors.lastname: Pattnaik
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D007150:Immunohistochemistry; D008253:Macaca mulatta; D010121:Oxytocin / Q000096:biosynthesis / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D055213:Retinal Pigment Epithelium / Q000196:embryology / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D012333:RNA, Messenger; D010121:Oxytocin
keywords: GPCR; cell-calcium; neuropeptide; oxytocin receptor; retinal pigment epithelium; signaling