Endocrine Abstracts

Vasopressin acts through G protein-coupled receptors on the cardiovascular and renal system to induce vasoconstriction and antidiuresis. Vasopressin also has important functions within the CNS influencing cognition, olfaction and a range of complex social interactions and behaviours. In addition, vasopressin has been reported in the mammalian retina and here we investigated the location and expression of vasopressin and vasopressin receptors (V1a, V1b, and V2) in the rat retina.

Transgenic Wistar rats expressing vasopressin-enhanced green fluorescent protein (vasopressin-eGFP) and wild-type controls (1–6 months of age: n=7; n=5) provided the retinal tissue. This was either fixed and processed for immunostaining to reveal the location of vasopressin containing neurons, or was snap frozen on dry ice and processed for mRNA extraction and cDNA production to investigate vasopressin, V1a, V1b and V2 receptor expression. Retinal sections (200–350 μm) were used for live cell imaging of eGFP positive cells and to enable the extraction of mRNA from single cells for subsequent RT-PCR.

Live and fixed retinas imaged using epifluorescent and confocal microscopy (n=4; n=5) showed the cell bodies of vasopressin-eGFP neurons to be located primarily within the inner nuclear layer of the retina with projections to the output ganglion cell layer. A small number of eGFP positive cells were also located in the ganglion cell layer. The specific distribution and structure of the neurons are consistent with the cells being amacrine in nature. Whole retinas were found to express significant amounts of vasopressin, V1a, and V1b receptor. Single cell PCR revealed that eGFP labelled cells expressed message for vasopressin and the V1a receptor.

In conclusion, the rat retina contains vasopressin positive neurons and message for V1a and V1b receptors. Further investigation will determine whether this is consistent with a physiological role for retinal vasopressin.