The morphology of relay neurons in the dorsal lateral geniculate nucleus of the marsupial brush-tailed possum (Trichosurus vulpecula).
The retinal terminal zones and the morphology of relay neurons within the dorsal lateral geniculate nucleus (LGNd) of the brush-tailed possum (Trichosurus vulpecula) have been investigated with horseradish peroxidase (HRP) tracing techniques. Anterograde transport of HRP from the retina confirmed previous descriptions of the laminar distribution of retinal afferents in this nucleus. In addition, it was found that lamina III consists of two adjacent bands (IIIa and IIIb) of contralateral retinal input, separated by a terminal-free zone 20-40 micron wide. This zone is not apparent with Nissl or fibre stains. Relay neurons in the LGNd were retrogradely filled following cortical injections of HRP, and two classes (A and B) were distinguished. Class A neurons are found in the alpha portion of the LGNd (laminae I, II, III, and IV) and class B neurons in the beta portion (laminae V, VI, and VII). Class A cells are more densely packed and have shorter and more numerous dendrites, less-extensive dendritic arbors, and thicker axons than class B cells. No significant differences were found between the two classes in perikaryal size or thickness of proximal dendrites. Neurons in each lamina of the nucleus have dendritic arbors which ramify extensively within adjacent laminae, except cells in lamina IIIb, which have relatively few dendrites that cross into the cell-free zone and lamina IV.
D000818:Animals; D002415:Cats; D005829:Geniculate Bodies / Q000166:cytology*; D009893:Opossums / Q000033:anatomy & histology*; D012160:Retina / Q000166:cytology; D013045:Species Specificity; D014795:Visual Pathways / Q000033:anatomy & histology