Journal of Neuroscience, Vol 7, 2785-2793, Copyright © 1987 by Society for Neuroscience
Tyrosine hydroxylase immunoreactivity in the rhesus monkey retina reveals synapses from bipolar cells to dopaminergic amacrine cells
JN Hokoc and AP Mariani
The synaptic organization of dopamine-containing amacrine cells in the
rhesus monkey retina was studied using immunohistochemistry of tyrosine
hydroxylase (TH), the rate-limiting enzyme in the catecholamine synthetic
pathway. Cell bodies of the TH-containing neurons were primarily in the
innermost tier of the inner nuclear layer. Their synaptic processes,
confined to the outermost stratum of the inner plexiform layer, contained
mostly small, clear vesicles and were presynaptic to unlabeled amacrine
cell processes and cell bodies at junctions that were symmetrical. Synapses
onto the TH-immunoreactive neurons were from bipolar cell axon terminals,
nonimmunoreactive amacrine cell processes, and other TH-containing amacrine
cells in a decreasing order of predominance. The bipolar cells were
presynaptic to the TH-containing neuronal processes at ribbon synapses. The
size, structure, and position of the bipolar cell axon terminals, which,
like the TH-reactive processes, were narrowly confined to the outermost
stratum of the inner plexiform layer, indicate that they are recently
described giant bistratified bipolar cells. The identification of this
bipolar cell input now provides evidence for a pathway from the outer
plexiform layer to dopaminergic amacrine cells in the inner plexiform layer
via a type of cone bipolar cell.