Human ganglion cells express the alpha-2 adrenergic receptor: relevance to neuroprotection.
OBJECTIVE
Alpha-2alpha adrenergic receptor (alpha(2)-AR) agonists are thought to be neuroprotective, preventing retinal ganglion cell death independent of pressure reduction. Previous studies have identified alpha(2)-ARs in rat retina. The authors aimed to demonstrate the presence and localisation of alpha(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 alpha(2A)-ARs was determined by antibody immunofluorescence.


RESULTS
alpha(2A)-AR expression was identified in the human retina, on ganglion cells, and cells in the inner and outer nuclear layers (INL, ONL). Differential alpha(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 alpha(2A)-ARs in undifferentiated cells and an increased expression upon fully differentiated cells.


CONCLUSIONS
alpha(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 alpha(2)-ARs on the RGC-5 cell line allows future investigation of these possible direct effects using in vitro glaucoma model systems.
Kalapesi
F B
FB
Department of Anatomy, University of New South Wales, Sydney NSW 2052, Australia.
Coroneo
M T
MT
Hill
M A
MA
D058647:Adrenergic alpha-2 Receptor Agonists; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D003315:Cornea / Q000378:metabolism; D006801:Humans; D018613:Microscopy, Confocal; D008875:Middle Aged; D018696:Neuroprotective Agents / Q000494:pharmacology; D051381:Rats; D018341:Receptors, Adrenergic, alpha-2 / Q000378:metabolism*; D012160:Retina / Q000166:cytology / Q000378:metabolism*; D012165:Retinal Ganglion Cells / Q000187:drug effects / Q000378:metabolism
D058647:Adrenergic alpha-2 Receptor Agonists; D018696:Neuroprotective Agents; D018341:Receptors, Adrenergic, alpha-2