Effects of PhXA41, a prostaglandin analogue, and PGF2αon the corneal and intraretinal d.c. electroretinogram (ERG) of the albino rabbit eye

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Abstract
PhXA41, a prostaglandin F2α analogue, is a new drug alternative for medical treatment of glaucoma. From earlier studies, it is known that certain prostaglandins (pgs) exert an influence on the d.c. electroretinogram (ERG). In the present study, possible effects of intraocular perfusion with PhXA41 (free acid) or PGF2α on the rabbit retina and retinal pigment epithelium (RPE) were evaluated. Unilateral vitrectomy was performed and a continuous intraocular perfusion was established, in which a reference solution was alternated with the test solution. In part one of the experiments, the corneal d.c. ERG and the standing potential of the eye (SP) were recorded from both eyes. In part two, vitreal and intraretinal d.c. ERG were recorded in the vitrectomized eye. PhXA41 and PGF2α produced similar effects, i.e. a significant and reversible c-wave increase at concentrations of 1–10 μg/ml. No influence was found in the concentration interval 10–100 ng/ml. There were no changes in a- and b-wave amplitudes at any of the concentrations tested. At a concentration of 10 μg/ml, the SP increased significantly. The intraretinal d.c. ERG showed a large reduction of slow PHI accompanied by a small change in transepithelial potential (TEP). Theoretically, a vitreous concentration of less than 1 ng/ml may be reached after topical application. This concentration level does not influence the d.c. ERG in this animal model. At higher concentrations, a significant and reversible c-wave increase seemed to be generated mainly in the inner retina by a reduction of slow PHI generated in the Müller cells. The effect of PhXA41 appears to be mediated by an FP receptor.