Differential effect of lithium on cell number in the hippocampus and prefrontal cortex in adult mice: a stereological study.

OBJECTIVES: Neuroimaging studies have revealed lithium-related increases in the volume of gray matter in the prefrontal cortex (PFC) and hippocampus. Postmortem human studies have reported alterations in neuronal and glial cell density and size in the PFC of lithium-treated subjects. Rodents treated with lithium exhibit cell proliferation in the dentate gyrus (DG) of the hippocampus. However, it is not known whether hippocampal and PFC volume are also increased in these animals or whether cell number in the PFC is altered. METHODS: Using stereological methods, this study estimated the total numbers of neurons and glia, and the packing density of astrocytes in the DG and PFC of normal adult mice treated with lithium, and evaluated the total volume of these regions and the entire neocortex. RESULTS: Lithium treatment increased the total numbers of neurons and glia in the DG (by 25% and 21%, respectively) and the density of astrocytes but did not alter total numbers in the PFC. However, the volumes of the hippocampus and its subfields, the PFC and its subareas, and the entire neocortex were not altered by lithium. CONCLUSIONS: Both neuronal and glial cells accounted for lithium-induced cell proliferation in the DG. That the numbers of neurons and glia were unchanged in the PFC is consistent with the view that this region is not a neurogenic zone. Further studies are required to clarify the impact of lithium treatment on the PFC under pathological conditions and to investigate the dissociation between increased cell proliferation and unchanged volume in the hippocampus.

Comparison of (stereotactic) parcellations in mouse prefrontal cortex.

This study compares the cytoarchitectonic parcellation of the prefrontal cortex (PFC) in the mouse as presented in publications that are commonly used for identifying brain areas. Agreement was found to be greater for boundaries in the medial PFC than in the lateral PFC and lowest for those in the orbital areas of the PFC. In this review, we explain and illustrate in a selected series of photographs and stereotactic pictures the differences in location and terminology of the different prefrontal cortical areas. The significance of cytoarchitectonic parcellation is discussed.

The rat orbital and agranular insular prefrontal cortical areas: a cytoarchitectonic and chemoarchitectonic study.

Cytoarchitectonic characterization of borders is necessary for stereological studies (e.g., total cell number estimation), in which particular cortical areas have to be defined. In this study, cytoarchitectonic characteristics are described and illustrated for the rat ventral or orbital frontal cortical areas, i.e., the lateral-, ventrolateral-, ventral- and medial-orbital areas; and for the lateral frontal cortical areas, i.e., the agranular insular and the dorsolateral orbital cortical area. Each cytoarchitectonic-defined boundary is corroborated by one or more of the immunocytochemical stainings for dopaminergic fibers, SMI-32 positive neurons, calbindin and parvalbumin positive neurons. Each immunocytochemical staining, however, shows a characteristic subset of the cytoarchitectonical borders. The dorsal agranular insular area (AId) and the dorsolateral orbital area (DLO) have been subdivided into a dorsal and a ventral part based upon differences between these parts in the Nissl and immunocytochemical stainings. The posterior part of VLO has a different structure and is, therefore, indicated as VLOp (VLO, posterior part).