The impact of maternal separation on adult mouse behaviour and on the total neuron number in the mouse hippocampus

The maternal separation paradigm has been applied to C57BL/6J mice as an animal developmental model for understanding structural deficits leading to abnormal behaviour. A maternal separation (MS) model was used on postnatal day (PND) 9, where the pups were removed from their mother for 24 h (MS24). When the pups were 10 weeks old, the level of anxiety and fear was measured with two behavioural tests; an open field test and an elevated plus maze test. The Barnes platform maze was used to test spatial learning, and memory by using acquisition trials followed by reverse trial sessions. The MS24 mice spent more time in the open arms of the elevated plus maze compared to controls, but no other treatment differences were found in the emotional behavioural tests. However, in the reverse trial for the Barnes maze test there was a significant difference in the frequency of visits to the old goal, the number of errors made by the MS24 mice compared to controls and in total distance moved. The mice were subsequently sacrificed and the total number of neurons estimated in the hippocampus using the optical fractionator. We found a significant loss of neurons in the dentate gyrus in MS mice compared to controls. Apparently a single maternal separation can impact the number of neurons in mouse hippocampus either by a decrease of neurogenesis or as an increase in neuron apoptosis. This study is the first to assess the result of maternal separation combining behaviour and stereology

Hippocampal pyramidal cells: the reemergence of cortical lamination

The increasing resolution of tract-tracing studies has led to the definition of segments along the transverse axis of the hippocampal pyramidal cell layer, which may represent functionally defined elements. This review will summarize evidence for a morphological and functional differentiation of pyramidal cells along the radial (deep to superficial) axis of the cell layer. In many species, deep and superficial sublayers can be identified histologically throughout large parts of the septotemporal extent of the hippocampus. Neurons in these sublayers are generated during different periods of development. During development, deep and superficial cells express genes (Sox5, SatB2) that also specify the phenotypes of superficial and deep cells in the neocortex. Deep and superficial cells differ neurochemically (e.g. calbindin and zinc) and in their adult gene expression patterns. These markers also distinguish sublayers in the septal hippocampus, where they are not readily apparent histologically in rat or mouse. Deep and superficial pyramidal cells differ in septal, striatal, and neocortical efferent connections. Distributions of deep and superficial pyramidal cell dendrites and studies in reeler or sparsely GFP-expressing mice indicate that this also applies to afferent pathways. Histological, neurochemical, and connective differences between deep and superficial neurons may correlate with (patho-) physiological phenomena specific to pyramidal cells at different radial locations. We feel that an appreciation of radial subdivisions in the pyramidal cell layer reminiscent of lamination in other cortical areas may be critical in the interpretation of studies of hippocampal anatomy and function

Análise comparativa de cortes de encéfalos humanos com coloração por três técnicas diferentes Comparative analysis of human brain slices with three different staining techniques

O estudo anatômico do encéfalo em cortes é facilitado empregando-se métodos de coloração para substância cinzenta. Os métodos mais freqüentemente empregados são os de Barnard, Robert e Brown, Mulligan e Green. O objetivo deste estudo foi determinar qual dessas técnicas apresenta melhores resultados com relação à diferenciação entre substâncias branca e cinzenta. Trinta cortes coronais de hemisfério cerebral humano foram submetidos às três técnicas, comparados entre si e analisados de acordo com três parâmetros estabelecidos: grau de diferenciação entre as substâncias branca e cinzenta; presença de linha única e contínua separando a substância branca do córtex cerebral; grau de impregnação da coloração em outros locais de substância branca. Atribuíram-se pontuações de 0 a 3 conforme a presença destes parâmetros, cada corte recebendo pontuação total que variava de 0 a 9. Após análise estatística, a técnica de Barnard, Robert e Brown apresentou média 8,33; a de Green 7,93 e a de Mulligan, 7,5, com diferença estatisticamente significativa.<br>Studing neuroanatomy at brain slices with gray matter staining techniques has several advantages. More often, the models described by Barnard, Robert and Brown, Mulligan, and Green are used. The aim of this study was to identify which of them achieves the best results on differentiation between the gray and the white matter. Thirty coronal slices of human brains underwent staining by the three techniques, and thus compared and analysed according this three parameters: degree of differentiation between white and gray matter, presence of a single and uninterrupted line dividing the white matter from the brain cortex; and degree of impregnation of the color staining in the white matter; scores from 0 to 3 have been given for the three parameters, with total score from 0 to 9. After statistic analysis, the Barnard, Robert and Brown model showed the best results, followed by Green's and Mulligan's