Abstract
Purpose: :
In order to understand the signaling effects of serotonin in the eye, this study was undertaken to characterize the localization and presence of 5-HT1A (5-hydroxytryptamine) and 5-HT7 receptors mRNA and their translated proteins in the ARPE-19 cells, rat and human retina.
Methods: :
The expression of 5-HT1A receptor message was determined using reverse transcriptase PCR (RT-PCR) in rat retina, human retina and a human retinal pigment epithelial (RPE) cell line (ARPE-19 cells). Levels of 5-HT1A receptor protein were determined using immunoblot analysis in rat retina, human retina and ARPE-19 cells. The localization of the 5-HT1A and 5-HT7 receptors was determined using immunohistochemistry.
Results: :
5-HT1A receptor mRNA as well as its protein was expressed in the rat retina, as determined by RT-PCR and immunoblotting respectively. For the first time, we have provided evidence that the human ARPE-19 cells and human retina contain the message and the protein for 5-HT1A receptor. Using immunocytochemistry we were able to visualize 5-HT1A receptors in the RPE, outer plexiform layer, and inner plexiform layer of the rat retina as well as in the ARPE 19 cells. However, in human retina we observed the 5-HT1A receptors in the RPE, cone inner segments, Mueller cell processes, and nerve fiber layer. The 5-HT7 receptor was found only in the inner retina ganglion cell layer.
Conclusions: :
5-HT1A receptors are present on RPE as well as in the synaptic layers of the retina. Therefore, this receptor is likely to be important in retinal signal processing and synaptic transmission. Furthermore, message and protein for the 5-HT1A receptors is conserved in the retina throughout various species, including human retina, rat, rabbit, and pig, signifying the importance of this receptor.
Keywords: receptors • retina • retinal pigment epithelium