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Prenatal development of central optic pathways in albino rats
Author(s) -
Lund R. D.,
Bunt Ann H.
Publication year - 1976
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.901650209
Subject(s) - optic tract , optic chiasm , superior colliculus , biology , anatomy , optic chiasma , geniculate , optic nerve , neuroscience , optic vesicle , diencephalon , lateral geniculate nucleus , superior colliculi , parvocellular cell , retina , visual system , optic cup (embryology) , neuropil , nucleus , central nervous system , eye development , biochemistry , gene , phenotype
The development of the central optic projections in albino rat fetuses has been studied using light and electron microscopic degeneration techniques and the horseradish peroxidase method for demonstrating axonal projections of neurons. The first optic axons to reach the region of the optic chiasm arrive at day 15. By day 16, a substantial optic chiasm is seen and the optic tract can be traced into the epithalamus, having first passed through the ventral lateral geniculate nucleus and a thin lamina of cells which is thought to correspond to part of the future dorsal lateral geniculate nucleus. A growth rate of 80–100 μm per hour is estimated for the fastest growing axons. By day 16‐1/3 the first axons have entered the anterior border of the superior colliculus and in the next day have grown across the entire rostrocaudal extent with the exception of the medial and lateral edges. The optic axons are recognized at day 17 as bundles lying just below the surface, but in older animals they come to lie deeper, as the whole layer of optic innervation broadens. The first synapses to be formed in the superior colliculus (some of them of optic origin) appear on day 17. Subsequently, there is a gradual increase in the number of contacts, the great majority being formed by optic axons. Compared with previous studies on Xenopus and chick, one of the most striking features of the development of the central visual connections in the rat is the relatively long time before the first optic axons reach the brain and the speed with which they innervate the central structures once they have arrived.