THE EFFECTS OF MYRISTYL GAMMA-PICOLINIUM CHLORIDE ON THE RABBIT RETINA - MORPHOLOGIC OBSERVATIONS

Purpose. This study was designed to localize the site of action of myr istyl gamma-picolinium chloride (MGP) in the rabbit retina and to eval uate the extent of the structural damage induced by the drug. Methods. The structural damage was assessed at the light microscopic level in eyes treated with various concentrations of MGP at different time inte rvals after intravitreal injection of the drug. Glial fibrillary acidi c protein (GFAP) immunoreactivity was tested in the same eyes and serv ed as an index of retinal damage. Results. The rabbit retinas, examine d about 1 mo after MGP injection, exhibited loss of photoreceptors and thinning of the retina in the regions close to the site of injection; remote retinal areas appeared morphologically intact or only slightly affected. Immunocytochemical analysis demonstrated the presence of GF AP in Muller (glial) cells throughout the entire retina. When the effe cts of MGP were examined at short time intervals (24 and 72 hr) after injection, severe morphologic damage in areas adjacent to the site of drug injection developed in parallel with the electroretinographic fin dings. However, GFAP could not be demonstrated. Conclusions. MGP, the preservative used in Depo-Medrol (Upjohn, Kalamazoo, MI), is highly to xic to the rabbit retina.