Synaptic organization of cholinergic amacrine cells in the rhesus monkey retina

In the rhesus monkey retina, choline acetyltransferase (ChAT) immunoreactivity has been used to study the localization and synaptic organization of cholinergic neurons by both light and electron microscopy with peroxidase‐antiperoxidase immunohistochemistry. ChAT‐containing neurons are a type of amacrine cell with 97.5% of their cell bodies localized to the ganglion cell layer and the remainder in the inner nuclear layer. Their processes arborize in a single narrow band in the inner plexiform layer in a plane diving the outer two‐thirds from the inner one‐third of this synaptic region. With electron microscopy, ChAT‐immunoreactive amacrine cell processes were observed to be primarily postsynaptic to the diffuse invaginating cone bipolar cells and presynaptic to ganglion cells, although they are both post‐ and presynaptic to immunohistochemically unlabeled amacrine cell profiles and to ChAT‐containing amacrine cell processes as well.