Catecholaminergic amacrine cells in the dog and wolf retina

• Published in: Visual Neuroscience
• Main Author: Peichl, Leo
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1991
• Subjects: Sensory Systems; Physiology; Canis lupus
• Online Access: http://dx.doi.org/10.1017/s0952523800010361; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0952523800010361

Abstract Catecholaminergic (presumed dopaminergic) amacrine cells in the retinae of Beagle dogs ( canis lupus f. familiaris ) and wolves ( canis lupus ) were visualized with an antiserum against tyrosine hydroxylase (TH). In both species, TH immunoreactivity is found in a population of amacrine cells with large somata (about 14 μm diameter) and large, moderately branched dendritic trees. Somata are located in the proximal inner nuclear layer (normal amacrines) or in the ganglion cell layer (displaced amacrines). Most dendrites stratify in a narrow band in the inner plexiform layer close to the inner nuclear layer, where they form a dense plexus with the characteristic pattern of “dendritic rings.” The displaced cells have some of their dendrites in a proximal stratum of the inner plexiform layer. A few immunopositive processes are found in the outer plexiform layer (interplexiform processes). In Beagle dogs, the cell density of catecholaminergic amacrines varies from less than 1/mm 2 in far periphery to 40–55/mm 2 in central retina (mean density 21/mm 2 ). The proportion of displaced amacrines varies locally from 10 to 85% (overall proportion 41% in one retina). In the wolf, densities of catecholaminergic cells range between about 3/mm 2 in peripheral and up to 35/mm 2 in central retina. The proportion of displaced cells is somewhat lower than in dogs, varying between 11 and 31% across the retina. The morphology and density distribution of canine catecholaminergic amacrines resemble that of other mammalian retinae. A marked difference, however, is the high percentage of displaced cells in both dog and wolf retina; it is the highest found in any mammal so far. The displaced and normal cells appear to be members of a single functional population. A comparison of the topographic distributions of catecholaminergic amacrines, rods, and ganglion cells in the dog retina shows no consistent density correlations between these neurons that are all part of the rod pathway.