An autoradiographic study of the development of the entorhinal and commissural afferents to the dentate gyrus of the Rat

Abstract

The development of the entorhinal, ipsilateral associational, and commissural afferents to the dentate gyrus have been studied autoradiographically, following the injection of small amounts of tritiated proline into the medial and lateral parts of the entorhinal cortex, and into fields CA3c and CA4 of the hippocampus, in a series of rats, on the third, sixth, and twelfth postnatal days. Clear labeling of the entorhinal afferents were found at the third postnatal day, and from the earliest stage studied the afferents from the two parts of the entorhinal cortex appear to be spatially segregated within the stratum moleculare of the dentate gyrus: the fibers from the lateral entorhinal area occupying the outermost one-third, or so, of this stratum, while those from the medial entorhinal cortex occupy its middle zone. The ipsilateral hippocampo-dentate associational pathway is present at the third postnatal day, but the commissural projection (which shares with it the inner part of the stratum moleculare) could not be labeled until the sixth postnatal day. By the twelfth day the characteristic adult pattern of distribution of the terminals of the two hippocampo-dentate pathways is established. Although this pattern is best accounted for on the basis of a temporal competition for the available synaptic sites on the proximal parts of the dendrites of the granule cells, the spatial segregation of these two fiber systems from those arising in the entorhinal cortex, is probably due to the selective fasciculation of fibers in each group of afferents and to their early cytochemical specificity.

Postnatal development of zinc-containing cells and neuropil in the hippocampal region of the mouse

“…In both species this gradient corresponds to the temporal pattern of c-a and entorhinal afferent ingrowth (Fricke and Cowan, 1977;Loy et al, 1977). However, the first appearance of staining in these layers in the mouse lags 2 (c-a) to 4 (lpp; observed at P9 by Stanfield and Cowan, 1979) days behind their appearance in the rat.…”

“…However, the first appearance of staining in these layers in the mouse lags 2 (c-a) to 4 (lpp; observed at P9 by Stanfield and Cowan, 1979) days behind their appearance in the rat. A segregation of lateral and medial entorhinal afferents is observed by P3 in the rat (Fricke and Cowan, 1977). At this age the mpp and lpp pathways cannot yet be distinguished based on their zinc content (Zimmer and Haug, 1978).…”

Latent Inhibition-Related Dopaminergic Responses in the Nucleus Accumbens are Disrupted Following Neonatal Transient Inactivation of the Ventral Subiculum

“…The neonatal blockade at PND8 may affect subicular developing fibers inasmuch as in the second week after birth the afferent and efferent connections of the SUB are still maturing (Schlessinger et al, 1975;Singh, 1977a, b;Fricke and Cowan, 1978). The establishment of neural networks depends in part on electrical activity involved in neuronal survival (Farber and Olney, 2003), synaptic proliferation (Marty et al, 2000), axons' myelination (Barres and Raff, 1993;Demerens et al, 1996;Zalc and Fields, 2000), the rearrangement of synaptic connections in the target structures (Stryker and Harris, 1986;Katz and Shatz, 1996;Hutchins and Kalil, 2008), and the maturation of dendritic spines (Drakew et al, 1999;Frotscher et al, 2000).…”

Role of apolipoprotein E and estrogen in mossy fiber sprouting in hippocampal slice cultures

“…Granule cell mossy fibers in the dorsal DG develop earlier (beginning at PD3) than in the ventral region, 35,65 and the granule cell terminal field in the ML as well as its entorhinal innervation develop earlier in the dorsal DG. 18,34,65 Developmental age of granule cells and their mossy projections may explain differential mossy fiber sprouting observed in the hippocampus septal-temporal axis. 12,34,57,69 Since 85% of granule cells are born postnatally and the mossy fiber system develops unusually slowly over the first three weeks postnatally, 20,65 the large increase in ApoE expression at this time 15,44,46 could play an important role in determining the consequences of neurodegeneration.…”