At least in hippocampal slices, organotypic cultures prepared from young adults also maintain synaptic activity in vivo, in WZ8040 EGFR/HER2 inhibitor contrast to cultures from peri-natal animals that sometimes display aberrant synaptic activity after long-term culture. It is unclear what cellular and cytoarchitectural distortions occur in the cerebral cortex during the development of neonatal tissue in culture, as key cortical neuronal populations are still in their migratory phase. It is therefore important to consider the interpretation of data from such organotypic models derived from early development for their relevance to experimental studies related to diseases and conditions that affect the mature nervous system. In this study, we investigated cell survival as well as the cellular and protein expression alterations that occur during the culture of whole brain slice cultures from neonates, young animals and mature adult mice. We show in this study the major advantages and limitations of using neonatal and mature brain tissue for long-term organotypic whole brain slice culture. We illustrate that neonatal mouse tissue survives long-term culture significantly better than tissue from more mature animals, and, after 14 DIV, proteins associated with a mature phenotype are expressed. However, the neuronal and glial organization of the cultured neonatal cortex is significantly different to that of mature brain slices, with increased expression of glial proteins throughout the cortex, loss of patterns of neuronal localization within distinct layers, no distinct glia limitans and the presence of what may be progenitor-like cells forming extensions from the periphery of the slice. Organotypic brain slice cultures are extensively used to investigate mechanistic insights into neuro- development, transmission and degeneration. The major limitation of organotypic brain slice culture techniques is determining the relative maturity of slices or to what extent cultured slices resemble that of living tissue in situ. In this regard, cultures are usually derived from neonatal tissue and maintained for an extended culture period. The rationale for culturing neonatal tissue is that the nerve cells survive explantation more readily as they are less vulnerable to hypoxic-ischemic damage. The results of the current study support this proposition illustrating that brain tissue derived from younger mice are significantly less vulnerable in long-term culture. For the pruposes of this study, we implemented a single culturing protocol for both neonatal and mature brain tissue. Previous studies, albeit related to hippocampal preparations, have suggested the possible benefits of increasing the oxygenation of dissecting medium as the mature brain is more vulnerable to hypoxic damage. Relatively few studies have attempted to culture adult tissue.