PURPOSETo investigate calcium signaling in a rat experimental model of glaucoma.METHODSA method for labeling ganglion cell layer (GCL) neurons with the calcium indicator Fura-2 in flat-mounted retinas of adult rats was established. Pharmacologically evoked responses in laser-induced glaucomatous and control retinas were imaged 2 weeks after the initial laser treatment. The optic nerves of the same eyes were evaluated for neurodegenerative changes.RESULTSAfter laser treatment, intraocular pressure (IOP) was elevated 1.5- to 4.9-fold (24.70 ± 15.57 mm Hg) compared with control eyes (8.71 ± 1.53 mm Hg), and the area of neurodegenerative axons in optic nerve sections of laser-treated eyes was increased by 1.2- to 13.3-fold. The basal intracellular Ca(2+) level, as revealed by the Fura-2 ratio, was elevated in GCL neurons of laser-treated eyes compared with controls. This might suggest a mild degree of damage at the level of the soma in the GCL neurons of eyes with elevated IOP. Although glaucomatous GCL neurons remained functional as assessed pharmacologically, analysis of imaging data revealed that responses evoked by a brief application of ATP were slightly reduced rather than increased in the cells of laser-treated eyes compared with controls. No significant relationships were found between IOP/optic nerve damage and functional characteristics (basal intracellular Ca(2+) level or response to carbachol/elevated K(+)/ATP) within cells of laser-treated eyes.CONCLUSIONSCa(2+) imaging is a useful tool to map altered physiological characteristics of individual GCL neurons in the glaucomatous eye.