Research report
Structural modifications associated with synaptic development in area CA1 of rat hippocampal organotypic cultures

https://doi.org/10.1016/0165-3806(93)90108-MGet rights and content

Abstract

Using morphological techniques, we characterized the developmental reorganization that takes place during the first weeks after explantation in area CA1 of organotypic hippocampal cultures maintained at the interface between medium and a CO2-enriched atmosphere. Pyramidal neurones redistributed from a vertical into an horizontal cell layer in the middle of a three-dimensional culture, with apical dendrites running above the pyramidal layer. Glial cells redistributed into a thin layer at the bottom of the culture, forming an interface between tissue and culture medium. Astrocytes were identified as the most numerous non neuronal cells. No sign of glial proliferation could be observed, except for a transient increase during the first days after explantation. The density of synaptic contacts in the stratum radiatum decreased immediately after explantation and then increased by about 20-fold to reach values in the proximal part of the apical layer after 4 weeks in culture which were only slightly smaller than those measured in 1-month-old rats. The synaptic density in the most distal part of the dendritic layer which receives connections extrinsic to the hippocampus remained significantly lower than in vivo. The ratio of spine to shaft contacts was comparable to that found in vivo. These results indicate that interface type of organotypic cultures can be used as an interesting model for studies of synaptic development in vitro.

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    Citation Excerpt :

    In this line, CA1 synapses at first postnatal days are prominently silent and it is hard to induce LTP on them during the first postnatal week, whereas robust LTP can be induced after the second week (Baudry et al., 1981; Harris and Teyler, 1984). Synaptogenesis occurs in the CA1 from P2 onwards (Amaral and Dent, 1981; Buchs et al., 1993), and spines become more stable and more mature between P15 and P35 (Fiala et al., 1998; Harris et al., 1992). Supporting our hypothesis, the dysregulation of other specific developmental expressed genes (Bhatt et al., 2009; van et al., 2013) or treatments with drugs during early life stages have been shown to induce long-term outcome effects in neural function and synaptic plasticity (Kataoka et al., 2013; Takuma et al., 2014; Xiao et al., 2016).

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