Abstract
Purpose: :
Endothelin ETB receptors have been suggested to contribute to neurodegeneration in glaucoma. The purpose of this study was to determine if there are changes in ETB receptor expression in vivo in the Morrison’s elevated IOP model of glaucoma in rats.
Methods: :
IOP elevation was carried out in one eye of adult male Brown Norway rats using the Morrison’s method (by injection of hypertonic saline through episcleral veins), while the contralateral eye served as control. Following intraocular pressure elevation, rats were maintained for 2 to 4 weeks and sacrificed. Retinal sections were obtained from control and IOP elevated rat eyes and analyzed for changes in ETB receptor expression by immunohistochemistry. Colocalization of ETB receptor immunostaining was carried out with a retinal ganglion cell marker using an antibody to neuritin, which is selectively expressed in retinal ganglion cells.
Results: :
IOP elevation produced an increase in ETB receptor expression in the retinal ganglion cells, inner plexiform layer and inner nuclear layer as determined by immunohistochemical analysis. An increased colocalization of ETB receptors with neuritin was also found mainly in retinal ganglions cells and inner plexiform layer in rat eyes with elevated IOP.
Conclusions: :
Increased intraocular pressure produced increased ETB receptor expression. Previous studies suggest that ETB receptor activation results in apoptotic cell death of retinal ganglion cells. Since ETB receptors mediate neurodegenerative effects, ETB receptor antagonists could be potential neuroprotective agents in glaucoma.
Keywords: neuroprotection • receptors: pharmacology/physiology • retina