Hippocampal neurogenesis and cortical cellular plasticity in Wahlberg's epauletted fruit bat: a qualitative and quantitative study.
ABSTRACT Species-specific characteristics of neuronal plasticity emerging from comparative studies can address the functional relevance of hippocampal or cortical plasticity in the light of ecological adaptation and evolutionary history of a given species. Here, we present a quantitative and qualitative analysis of neurogenesis in young and adult free-living Wahlberg's epauletted fruit bats. Using the markers for proliferating cell nuclear antigen (PCNA), bromodeoxyuridine (BrdU), doublecortin (DCX) and polysialic acid neural cell adhesion molecule (PSA-NCAM), our findings in the hippocampus, olfactory bulb and cortical regions are described and compared to reports in other mammals. Expressed as a percentage of the total number of granule cells, PCNA- and BrdU-positive cells accounted for 0.04 in young to 0.01% in adult animals; DCX-positive cells for 0.05 (young) to 0.01% (adult); PSA-NCAM-positive cells for 0.1 (young) to 0.02% (adult), and pyknotic cells for 0.007 (young) to 0.005% (adult). The numbers were comparable to other long-lived, late-maturing mammals such as primates. A significant increase in the total granule cell number from young to adult animals demonstrated the successful formation and integration of new cells. In adulthood, granule cell number appeared stable and was surprisingly low in comparison to other species. Observations in the olfactory bulb and rostral migratory stream were qualitatively similar to descriptions in other species. In the ventral horn of the lateral ventricle, we noted prominent expression of DCX and PSA-NCAM forming a temporal migratory stream targeting the piriform cortex, possibly reflecting the importance of olfaction to these species. Low, but persistent hippocampal neurogenesis in non-echolocating fruit bats contrasted the findings in echolocating microbats, in which hippocampal neurogenesis was largely absent. Together with the observed intense cortical plasticity in the olfactory system of fruit bats we suggest a differential influence of sensory modalities on hippocampal and cortical plasticity in this mammalian order.
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ABSTRACT: In the adult mammalian brain, two neurogenic regions have been characterized, the subventricular zone (SVZ) of the lateral ventricle (LV) and the subgranular zone (SGZ) of the dentate gyrus (DG). Despite remarkable knowledge in rodents, the detailed arrangement of neurogenic regions in most mammals is poorly understood. In this study, we used immunohistochemistry and cell type-specific antibodies to investigate the organization of two germinal regions in the adult ferret, which belongs to the order Carnivora and is widely used as a model animal with a gyrencephalic brain. From the SVZ to the olfactory bulb, doublecortin-positive cells tended to organize in chain-like clusters, which were surrounded by a meshwork of astrocytes. This structure was homologous to the rostral migratory stream (RMS) described in other species. Different from rodents, the horizontal limb of the RMS emerged directly from the LV, and the anterior region of the LV extended rostrally and reached the olfactory bulb. In the DG, glial fibrillary acidic protein-positive cells with long radial processes as well as doublecortin-positive cells were oriented in the SGZ. In both regions, doublecortin-positive cells showed characteristic morphology and were positive for polysialylated-neural cell adhesion molecule, beta-III tubulin, and lamin B1 (intense staining). Proliferating cells were detected in both regions using antibodies against proliferating cell nuclear antigen and phospho-histone H3. These observations demonstrate that the two neurogenic regions in ferrets have similar cellular composition as those of other mammalian species despite anatomical differences in the brain. J. Comp. Neurol., 2013. © 2013 Wiley Periodicals, Inc.The Journal of Comparative Neurology 11/2013; 522(8). · 3.51 Impact Factor
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ABSTRACT: Neurogenesis, the formation of new neurons, can be observed in the adult brain of many mammalian species, including humans. Despite significant progress in our understanding of adult neurogenesis, we are still missing data about the extent and location of production of neural precursors in the adult mammalian brain. We used 5-ethynyl-2'-deoxyuridine (EdU) to map the location of proliferating cells throughout the entire adult mouse brain and found that neurogenesis occurs at two locations in the mouse brain. The larger one we define as the main proliferative zone (MPZ), and the smaller one corresponds to the subgranular zone of the hippocampus. The MPZ can be divided into three parts. The caudate migratory stream (CMS) occupies the middle part of the MPZ. The cable of proliferating cells emanating from the most anterior part of the CMS toward the olfactory bulbs forms the rostral migratory stream. The thin layer of proliferating cells extending posteriorly from the CMS forms the midlayer. We have not found any additional aggregations of proliferating cells in the adult mouse brain that could suggest the existence of other major neurogenic zones in the adult mouse brain.PLoS ONE 11/2014; 9(11):e111453. · 3.53 Impact Factor
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ABSTRACT: A previous study investigating potential adult hippocampal neurogenesis in microchiropteran bats failed to reveal a strong presence of this neural trait. As microchiropterans have a high field metabolic rate and a small body mass, it is possible that capture/handling stress may lead to a decrease in the detectable presence of adult hippocampal neurogenesis. Here we looked for evidence of adult hippocampal neurogenesis using immunohistochemical techniques for the endogenous marker doublecortin in 10 species of microchiropterans euthanized and perfusion fixed at specific time points following capture. Our results reveal that when euthanized and perfused within 15 minutes of capture, abundant putative adult hippocampal neurogenesis could be detected using doublecortin immunhistochemistry. Between 15 and 30 minutes post-capture, the detectable levels of doublecortin dropped dramatically and after 30 minutes post-capture, immunohistochemistry for doublecortin could not reveal any significant evidence of putative adult hippocampal neurogenesis. Thus, as with all other mammals studied to date apart from cetaceans, bats, including both microchiropterans and megachiropterans, appear to exhibit substantial levels of adult hippocampal neurogenesis. The present study underscores the concept that, as with laboratory experiments, studies conducted on wild-caught animals need to be cognizant of the fact that acute stress (capture/handling) may induce major changes in the appearance of specific neural traits.Neuroscience 08/2014; · 3.33 Impact Factor