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Human ganglion cells express the alpha-2 adrenergic receptor: relevance to neuroprotection

¹ Cell Biology Laboratory, Department of Anatomy, School of Medical Sciences, University of New South Wales, Sydney 2052, Australia
² Department of Ophthalmology, Prince of Wales Hospital, University of New South Wales, Sydney 2052, Australia

Correspondence to:
Correspondence to:
Dr Mark Hill
Department of Anatomy, University of New South Wales, Sydney NSW 2052, Australia; m.hill{at}unsw.edu.au

Background/aim: Alpha-2 adrenergic receptor (₂-AR) agonists are thought to be neuroprotective, preventing retinal ganglion cell death independent of pressure reduction. Previous studies have identified ₂-ARs in rat retina. The authors aimed to demonstrate the presence and localisation of ₂-ARs in human and rat retina and on the rat retinal ganglion cell line, RGC-5.

Methods: Seven postmortem human and three postmortem rat eyes were paraformaldehyde fixed and frozen. RGC-5 cells were also paraformaldehyde fixed. The expression of _2A-ARs was determined by antibody immunofluorescence.

Results: _2A-AR expression was identified in the human retina, on ganglion cells, and cells in the inner and outer nuclear layers (INL, ONL). Differential _2A-AR staining patterns in the INL and ONL suggest a further restriction to as yet unidentified neuronal subclasses. The RGC-5 cell line also expressed _2A-ARs in undifferentiated cells and an increased expression upon fully differentiated cells.

Conclusion: ₂-AR agonists in addition to their pressure lowering effects in the eye, may act directly upon retinal neurons, including retinal ganglion cells. The presence of ₂-ARs on the RGC-5 cell line allows future investigation of these possible direct effects using in vitro glaucoma model systems.

Abbreviations: ₂-AR, alpha-2 adrenergic receptor; CRALBP, cellular retinaldehyde binding protein; GCL, ganglion cell layer; INL, inner nuclear layer; ONL, outer nuclear layer; PBS, phosphate buffered saline

Keywords: human ganglion cells; alpha-2 receptors

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