Laminar differentiation of the hippocampus, fascia dentata and subiculum in developing rats, observed with the timm sulphide silver method

Abstract

The laminar staining of the rat hippocampal region with the Timm sulphide silver method is from studies on adult rats known to depend on the various fibersystems terminating in these laminae. In order to illustrate the development of these fibersystems the laminar differentiation of the Timm staining of fascia dentata, hippocampus and subiculum is presented for rats between 1 and 31 days old. Corresponding changes in cytoarchitectonics as revealed by thionin staining are briefly demonstrated. Even on the first postnatal day there are indications of the mature, laminar staining pattern, and between three and nine days all the laminae corresponding to the terminal fields of the major afferent and intrinsic systems appear. After 12 days only minor additions to the laminar pattern develop, but there are adjustments of absolute and relative dimensions of layers and fields, and also the staining densities of individual laminae change. These observations are in good correlation with the available information on both hippocampal neurogenesis and cytodifferentiation, and the few fiber tracing studies performed on the developing hippocampal region. Compared to the latter, which ideally marks only one system or one lamina per animal, the Timm method provides an excellent means for getting an overview of the general developmental situation at the different ages. Thus developmental gradients along septotemporal, medio-lateral and basal-apical axes are found; which should be heeded in future studies on hippocampal synaptogenesis. The observations are discussed in relation to current models for neuronal growth and formation of nervous connections.

Elimination of zinc from synaptic vesicles in the intact mouse brain by disruption of the ZnT 3 gene

“…Histochemically reactive zinc is present in many regions of the central nervous system (7,8) and is especially abundant in the hippocampus (7,9,10).…”

Early Histological Maturation in the Hippocampus of the Guinea Pig

“…Newborn altricial mammals have no vesicular zinc in their cerebral cortex and hippocampus. Vesicular zinc loading occurs postnatally in altricial species that have been studied [Sanchez-Andres et al, 1997;Slomianka and Geneser, 1997;Zimmer and Haug, 1978]. In addition to the immaturity of principal hippocampal neuron circuitry, non-principal hippocampal neurons, mainly GABAergic and inhibitory in the adult condition, also appear immature in the newborn altricial hippocampus.…”

“…The guinea pig seems to be an optimal model to answer this question as its hippocampus shows some degree of maturity 5 days after birth (P5) [Wolfer and Lipp, 1995] and the hippocampus has been relatively well studied in adult specimens [Zimmer and Haug, 1978].…”

Hippocampal Maturation in the Precocial Murid Rodent <i>Acomys cahirinu</i><i>s</i>

“…In Timm-stained material, both the dentate gyrus and hippocampus are recognizable in the early postnatal period, but lamina tion does not become distinct until be- tween 3 and 9 days post partum [2,22], In contrast, the hippocampal formation of the newborn Acomys has a very mature ap pearance ( fig. 1).…”

“…In the following study, the growth o f the hip pocampal formation in Acomys was as sessed. The hippocampus has many attrac tive characteristics for comparative stud ies of brain growth, including: (I) its clear ly laminated structure, which facilitates measurement of volumetric growth, (2) its pattern of late maturation, which allows for concentration on the postnatal period, and (3) the considerable information available on anatomical development in altricial murids [3,6,7,11,17,19,22], as well as in other species [13][14][15]18]. …”