OXT-OXTR pathway active in posterior retina

The posterior retina is a site of oxytocin (OXT) activation of the oxytocin receptor (OXTR), which may serve as a paracrine signalling pathway contributing to communication between the retinal pigment epithelium and the cone photoreceptor, according to a study published online in Investigative Ophthalmology and Visual Science.

Researchers from the University of Wisconsin (USA), used immunohistochemistry using cell specific markers to localize OXT within a rhesus retina, and reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry to assess the expression of OXTR in both rhesus and human retinas.

To determine the expression of OXTR in cultured human foetal retinal pigment epithelium (hfRPE) cells, the researchers used single-cell RT-PCR and Western blot analyses. To assess transient mobilization of intracellular Ca2+ ([Ca2+]i), the hfRPE cells were loaded with Fura-2-acetoxymethyl ester and studied by ratiometric Ca2+ imaging.

They found that, in the rhesus retina, OXT was expressed in the cone photoreceptor extracellular matrix, and OXTR mRNA and protein were expressed in both the human and rhesus retinal pigment epithelium. In the cultured hfRPE cells, OXTR mRNA and protein expression were observed, and a transient increase of [Ca2+]i was induced by exposure of these cells to 100 nM OXT.

The researchers concluded that OXT and OXTR are present in the posterior retina and OXT causes an increase in hfRPE [Ca2+]i , suggesting that the retina is an active site of the OXT-OXTR signaling pathway.