Abstract
Purpose: :
Prolactin (PRL) is synthesized and cleaved to antiangiogenic PRL fragments in retinal tissue, and these molecules inhibit retinal blood vessel growth and dilation (IOVS 46:2947, 2005). To further investigate the actions of retinal PRL, we have mapped the expression of PRL and of the PRL receptor (PRLR) in the retina of adult rats.
Methods: :
Cellular distribution of PRL and PRLR was examined by in situ hybridization and double immunolabeling using antibodies directed against glutamine synthetase (GS, labeling Müller cells), glial fibrillary acidic protein (GFAP, labeling astrocytes), or neuronal nuclei (NeuN, labeling neurons).
Results: :
PRL mRNA was found mostly in the outer nuclear layer (ONL) and ganglion cell layer (GCL), with fewer positive cells in the outer plexiform layer (OPL) and inner nuclear layer (INL). Consistent with this finding, PRL–immunoreactivity was observed in the external segments of the photoreceptors, the INL, the inner plexiform layer (IPL) and in the GCL. PRL colocalized with NeuN in cells within the INL and GCL, and with GS in cellular somas and projections throughout the retina, but not with the GFAP–containing processes of the GCL. The PRLR mRNA was primarily located in the ONL and in the INL with fewer labeled cells in the GCL. Likewise, the PRLR was distributed in the ONL, the INL, and the GCL, and also in the IPL.
Conclusions: :
PRL and PRLR are expressed throughout the retina in photoreceptors, Müller cells, interneurons, and ganglion cells, but not in astrocytes. These findings suggest that retinal PRL molecules function as local regulators of various cell types in the retina.
Keywords: retina • neuropeptides • immunohistochemistry