Choline Acetyltransferase Depletion in the Rat Retina After Intraocular Injection of Neurotoxins

The effects of kainic acid (KA), quisqualic acid (QA), and ibotenic acid (IBO) on histology of the retina and on the retinal choline acetyltransferase (ChAT) activity were studied in the rat. KA produced the highest number of altered cells in the ganglion cell layer (GCL) and in the inner nuclear layer (INL), with an almost complete depletion of ChAT activity. QA was less effective than KA in terms of both the number of altered cells and in ChAT depletion. In contrast, retinas injected with IBO showed the mildest morphological lesions together with the highest reduction in the enzyme activity. These results indicate that IBO affects nearly all the cholinergic neurons in the rat retina, whereas other populations, sensitive to KA or QA, are spared. Because of this higher specificity toward the cholinergic subpopulation, IBO may be a useful tool when cholinergic cells need to be destroyed in the retina.