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Laboratory science - Extended reports
Human ganglion cells express the alpha-2 adrenergic receptor: relevance to neuroprotection
  1. F B Kalapesi1,
  2. M T Coroneo2,
  3. M A Hill1
  1. 1Cell Biology Laboratory, Department of Anatomy, School of Medical Sciences, University of New South Wales, Sydney 2052, Australia
  2. 2Department of Ophthalmology, Prince of Wales Hospital, University of New South Wales, Sydney 2052, Australia
  1. Correspondence to: Dr Mark Hill Department of Anatomy, University of New South Wales, Sydney NSW 2052, Australia; m.hillunsw.edu.au

Abstract

Background/aim: Alpha-2α adrenergic receptor (α2-AR) agonists are thought to be neuroprotective, preventing retinal ganglion cell death independent of pressure reduction. Previous studies have identified α2-ARs in rat retina. The authors aimed to demonstrate the presence and localisation of α2-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 α2A-ARs was determined by antibody immunofluorescence.

Results: α2A-AR expression was identified in the human retina, on ganglion cells, and cells in the inner and outer nuclear layers (INL, ONL). Differential α2A-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 α2A-ARs in undifferentiated cells and an increased expression upon fully differentiated cells.

Conclusion: α2-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 α2-ARs on the RGC-5 cell line allows future investigation of these possible direct effects using in vitro glaucoma model systems.

  • α2-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
  • human ganglion cells
  • alpha-2 receptors
  • α2-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
  • human ganglion cells
  • alpha-2 receptors

https://doi.org/10.1136/bjo.2004.053025

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    Footnotes

    • Competing interests: The authors have no competing or financial interests.

    • Ethics approval: University of New South Wales, Human Research Ethics Committee Approval 03225; University of New South Wales, Animal Care and Ethics Committee Approval 1997/101.