Autoradiographic Study of Development of the Cerebral Cortex in the Rabbit

Abstract

The histogenetic development of the archi-, paleo-and neocortex of the rabbit has been studied using autoradiographic techniques. The analysis is based upon a series of 54 embryos and newborn rabbits, whose mothers were injected on successive days of gestation with a single dose of tritiated thymidine. Neurons destined to form the cerebral cortex originate in the matrix layer surrounding the lateral ventricles. From the matrix, cells migrate to form the different cortical layers in an inside-out sequence. This sequence appears reversed in the fascia dentata. In the anterior region of the brain, a single developmental gradient of histogenesis of the cortex is observed. This gradient starts in the ventralmost areas of the cortex and then advances in a dorso-medial direction. In the posterior region of the brain, there are two gradients of cortical histogenesis. These gradients start at the lateral aspect of the cortex. One advances in a ventromedial direction and the other in a dorsomedial direction. The archi and neocortex of both anterior and posterior regions of the brain appear to develop synchronously. However, the paleocortex of the anterior regions of the brain (prepyriform cortex) leads in its development the paleocortex of the posterior regions of the brain (entorhinal cortex and perirhinal cortex).

Neurogenesis in a Marsupial: The Brush-Tailed Possum <i>(Trichosurus vulpecula)</i>

“…[1989]. ' Fernandez and Bravo [ 1974], Fernandez et al [ 1979]. ' Rakic[1973' Rakic[ ,1982, Brand and Rakic[1979], Kostovicand Rakic[1980], Gould and Rakic [1981].…”

Subgranular Zone of the Dentate Gyrus of Young Rabbits As a Secondary Matrix

“…As studies dealing with neurogenesis in the rabbit dentate gyrus have all focused up on the prenatal period [13,22], we decided to investigate the proliferative ability of subgranular cells in 2-month-old rabbits using 3H-thymidine autoradiography. Moreover, as no systematic ultrastructural study of post natal granule neuron morphogenesis existed, we decided to follow, by electron microscope autoradiography, the fate of the labelled cells as a function of survival time.…”

Autoradiographic Study of the Development of the Neostriatum in the Rabbit

“…5, 6). This difference appears to be associated with the cortical developmental gradient that advances following a similar direction through the neocortex [Fernandez and Bravo, 1974], The ventromedial to dorsolateral gradient coexists with a caudal to rostral gradient. In fact, the distribution of la belled cells in the developing neostriatum is not uniform in the rostrocaudal axis; regions located caudally develop earlier than the rostral regions.…”

“…This occurs according to an outside-inside sequence [Fernandez, 1969;Angevine, 1970;Fernandez and Bravo, 1973;MacAllister, 1976], In the cerebral cortex, the pattern of development along the outside-inside axis has an inverse direction to that observed in the thalamus. The cells destined to form the deep cortical layers are laid close to the matrix at early stages of development, and the cells which form the most superficial layers arise later and migrate through the previously formed layers [Berry and Rogers, 1965;Fernan dez, 1969;Shimada and Longman, 1970;Fernandez and Bravo, 1974;Bruckner el al., 1976;Lund and Musiari, 1977], In this way, in the thal amic nuclei and cerebral cortical development, cells originating at differ ent times are located at different distances from the corresponding matrix layer. In the neostriatum, in contrast, if we consider any imaginary col umn of cells roughly perpendicular to the surface of the matrix layer from where they were generated, we find that at later stages of neostriatal de velopment the number of grains in each one of the cells that form the col umn is on the average the same; this proves that most of these cells are iso chronic in their origin ( fig.…”