The Histochemical Changes of Cholinesterase Activity in Rabbit's Retinae at Early Postnatal Stages

ABSTRACT

The authors studied histochemically the enzymatic sites of retinal cholinesterase activity in the albino rabbit during different early postnatal periods. The retinae of young rabbits weighing approximately 60gm. whose palpebrae were still fused and unable to function for sight, and of rabbits weighing approximately 300gm. which were able to see, were obtained immediately after killing the animals by the intravenous injection of air or by decapitation and fixed in formalin-sucrose ammonia fixative, as recommended by Pearson (1963), for about 24 hours and incubated in the substrate containing acetylthiocholine, iodide, as presented by Gerebtzoff (1953), at 37degrees C. for 2 to 3 hours. After the treatment of the retinae, as devised by Koelle and Friedenwald (1950), the retinae were sectioned at 5 micra and mounted both without counterstaining and after counterstaining with hematoxylin alone. In young rabbits weighing approximately 60gm., moderate cholinesterase activity was observed only in the ganglion cells of the retinae and slight enzymatic activity was faintly apparent in the layer of the optic nerve fibers. No enzymatic activity was recognized in the remaining layers of the retinae. In rabbits weighing approximately 300gm. the retinae showed different enzymatic distribution compared to the former. The cholinesterase activity was diversely distributed compared to the former and was localized in the inner nuclear layer, inner plexiform layer, and the ganglion cells showing moderate to slight activity.