0000000000084383
AUTHOR
Gregori Alonso-llosa
NMDA receptor antagonist treatment increases the production of new neurons in the aged rat hippocampus
The production of new neurons declines during adulthood and persists, although at very low levels, in the aged hippocampus. Since neurogenesis in young adults has been related to learning and memory, its reduction may contribute to the age-related impairments in these abilities. Adrenalectomy (ADX) enhances neurogenesis in the aged hippocampus, although it also induces neuronal cell death. Since the administration of an NMDA receptor antagonist enhances neurogenesis in young adult rats without deleterious morphological effects, we have tested whether neurogenesis could be reactivated in aged rats. Our study shows that cell proliferation, cell death, neurogenesis and the number of radial gli…
The lizard cerebral cortex as a model to study neuronal regeneration
The medial cerebral cortex of lizards, an area homologous to the hippocampal fascia dentata, shows delayed postnatal neurogenesis, i.e., cells in the medial cortex ependyma proliferate and give rise to immature neurons, which migrate to the cell layer. There, recruited neurons differentiate and give rise to zinc containing axons directed to the rest of cortical areas, thus resulting in a continuous growth of the medial cortex and its zinc-enriched axonal projection. This happens along the lizard life span, even in adult lizards, thus allowing one of their most important characteristics: neuronal regeneration. Experiments in our laboratory have shown that chemical lesion of the medial cortex…
PSA-NCAM expression in the piriform cortex of the adult rat. Modulation by NMDA receptor antagonist administration.
Administration of NMDA receptor antagonists upregulates the expression of the polysialylated form of the neural cell adhesion molecule (PSA-NCAM) in the adult hippocampus. Since the piriform cortex is also populated by PSA-NCAM immunoreactive neurons during adulthood, we sought to characterize them in detail and to test whether NMDA receptor antagonists also modulate PSA-NCAM in this cortical region. PSA-NCAM immunoreactivity is located mainly in layer II, where many neurogliaform and some pyramidal-semilunar transitional neurons are labeled. Many large neurons in layer III and endopiriform nucleus also express PSA-NCAM. Interestingly, some small labeled cells resembling migratory neuroblas…
Olfactory bulbectomy, but not odor conditioned aversion, induces the differentiation of immature neurons in the adult rat piriform cortex.
International audience; The piriform cortex layer II of young-adult rats presents a population of prenatally generated cells, which express immature neuronal markers, such as the polysialylated form of the neural cell adhesion molecule (PSA-NCAM) or doublecortin (DCX), and display structural characteristics of immature neurons. The number of PSA-NCAM/DCX expressing cells in this region decreases markedly as age progresses, suggesting that these cells differentiate or die. Since the piriform cortex receives a major input from the olfactory bulb and participates in olfactory information processing, it is possible that the immature neurons in layer II are affected by manipulations of the olfac…
Capture of extracellular zinc ions by astrocytes.
Synaptic zinc ions released during synaptic transmission interact with pre- and postsynaptic neuroreceptors, thus modulating neurotransmission. It is likely that they have to be efficiently cleared from the extracellular milieu to assure subsequent synaptic events. Both neurons and glia are assumed to participate in this clearance by mechanisms that are not fully understood. In this study, electron microscopic zinc cytochemistry has shown zinc-electrondense particles associated with hippocampal astrocytic membranes frequently found accumulated in stacked lamellae. In cultured astrocytes, the use of zinc fluorochromes and endocytic markers allowed the simultaneous imaging of the capture of e…
Neurons of the dentate molecular layer in the rabbit hippocampus.
The molecular layer of the dentate gyrus appears as the main entrance gate for information into the hippocampus, i.e., where the perforant path axons from the entorhinal cortex synapse onto the spines and dendrites of granule cells. A few dispersed neuronal somata appear intermingled in between and probably control the flow of information in this area. In rabbits, the number of neurons in the molecular layer increases in the first week of postnatal life and then stabilizes to appear permanent and heterogeneous over the individuals' life span, including old animals. By means of Golgi impregnations, NADPH histochemistry, immunocytochemical stainings and intracellular labelings (lucifer yellow…
NMDA receptor antagonist treatment induces a long-lasting increase in the number of proliferating cells, PSA-NCAM-immunoreactive granule neurons and radial glia in the adult rat dentate gyrus
During adulthood, neural precursors located in the subgranular zone of the dentate gyrus continue to proliferate, leading to the generation of new granule neurons. These recently generated cells transiently express the polysialylated form of the neural cell adhesion molecule, PSA-NCAM, and are supported by radial glia-like cells that are likely to play a role in neuronal migration and differentiation, or even act as their precursors. Previous reports indicate that treatment with NMDA receptor antagonists stimulates adult neurogenesis in the dentate gyrus, and because of the potential therapeutic value of this approach, we were interested in further characterizing the consequences of pharmac…
Divergent impact of the polysialyltransferases ST8SiaII and ST8SiaIV on polysialic acid expression in immature neurons and interneurons of the adult cerebral cortex.
Polysialic acid (PSA) is a negatively charged carbohydrate polymer, which confers antiadhesive properties to the neural cell adhesion molecule NCAM and facilitates cellular plasticity during brain development. In mice, PSA expression decreases drastically during the first postnatal weeks and it gets confined to immature neurons and regions displaying structural plasticity during adulthood. In the brain, PSA is exclusively synthesized by the two polysialyltransferases ST8SiaII and ST8SiaIV. To study their individual contribution to polysialylation in the adult, we analyzed PSA expression in mice deficient for either polysialyltransferase. Focusing on the cerebral cortex, our results indicate…