Acetylcholinesterase localization in cat retina: a comparison with choline acetyltransferase

Cytochemical localization of acetylcholinesterase (AChE) in cat retina showed reactivity in at least two types of amacrine cell and in essentially all of the cells in the ganglion-cell layer. Reaction product was present throughout the inner plexiform layer (IPL) with heavier accumulations forming bands at 0-6% and 64-78% depth levels. All of the reactivity was abolished by incubation with BW 284c51, a specific inhibitor of AChE. After pretreatment of animals with diisopropylfluorophosphate, new enzyme was synthesized by both amacrine and ganglion cells. In contrast, choline acetyltransferase immunoreactivity was limited to matching subpopulations of amacrine (A14) and displaced amacrine (dA14) cells, ramifying narrowly at 20% and 49% depth levels within the IPL. Combined localization of both enzymes in the same tissue confirmed the presence of AChE in cholinergic cells. However, the greatest concentration of AChE in the IPL was in strata not receiving direct cholinergic input. These findings affirm that AChE is not a reliable marker for either cholinergic or cholinoceptive neurons. The distribution of AChE in the cat retina suggests that this enzyme may participate in functions not directly related to cholinergic neurotransmission.