title: Maturation of neurons in neocortical slice cultures: A light and electron microscopic study on in situ and in vitro material.
abstract: Using light and electron microscopic methods, we investigated the development and morphology of neurons in neocortical slice cultures. Slices taken from the visual cortex of 6-day-old rats and cultivated for 14 or 20 days were compared with in situ material of corresponding age (P 20 and P 26). Maturation and differentiation of pyramidal and non-pyramidal cells kept in vitro were found to have progressed considerably. In the light microscope the neurons exhibited a morphological appearance strikingly similar to that of the neurons of the neocortex in situ at the same age. The fine structure of the tissue in vitro also had a mature appearance, corresponding in most respects to the material in situ. Synapses and dendritic spines were well-developed. Sometimes a spine apparatus was contained in the sections and occasionally a myelinated fiber could be seen. GABA-immunoreactive cells making symmetric synaptic contacts were also present. Despite these similarities, some quantitative differences could be observed. In slice cultures, only 52% of the synapses were located on spines (78% in situ). In vitro, a larger proportion of synapses (30%) showed a postsynaptically concave curvature than was the case in situ (12%). The areal density of synapses in vitro reached only about 70% of that in situ. This was probably a side-effect of the larger size of dendritic and axonal profiles on electron micrographs of in vitro-material. The most striking difference was that large synapses and synapses containing a large amount of synaptic vesicles were considerably more frequent in vitro than in situ.
mesh_terms: D000818:Animals; D002540:Cerebral Cortex / Q000166:cytology* / Q000648:ultrastructure; D003712:Dendrites / Q000648:ultrastructure; D008854:Microscopy, Electron; D016253:Microscopy, Immunoelectron; D009474:Neurons / Q000166:cytology* / Q000648:ultrastructure; D009924:Organ Culture Techniques / Q000379:methods; D011712:Pyramidal Tracts / Q000166:cytology / Q000648:ultrastructure; D051381:Rats; D013194:Staining and Labeling; D013569:Synapses / Q000648:ultrastructure; D013997:Time Factors; D014793:Visual Cortex / Q000166:cytology* / Q000648:ultrastructure; D005680:gamma-Aminobutyric Acid / Q000032:analysis*
chemical_list: D005680:gamma-Aminobutyric Acid