Neuroscience
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Dissociated cortical neurons from rat embryos cultured onto micro-electrode arrays exhibit characteristic patterns of electrophysiological activity, ranging from isolated spikes in the first days of development to highly synchronized bursts after 3-4 weeks in vitro. In this work we analyzed these features by considering the approach proposed by the self-organized criticality theory: we found that networks of dissociated cortical neurons also generate spontaneous events of spreading activity, previously observed in cortical slices, in the form of neuronal avalanches. Choosing an appropriate time scale of observation to detect such neuronal avalanches, we studied the dynamics by considering the spontaneous activity during acute recordings in mature cultures and following the development of the network. ⋯ Finally, a computational model of neuronal network was developed in order to interpret the experimental results and understand which parameters (e.g. connectivity, excitability) influence the distribution of avalanches. In summary, cortical neurons preserve their capability to self-organize in an effective network even when dissociated and cultured in vitro. The distribution of avalanche features seems to be critical in those cultures displaying medium synchronization among bursts and poor random spiking activity, as confirmed by chemical manipulation experiments and modeling studies.
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The prefrontal cortex is continuously required for working memory processing during wakefulness, but is particularly hypoactivated during sleep and in psychiatric disorders such as schizophrenia. Ammon's horn CA1 hippocampus subfield (CA1) afferents provide a functional modulatory path that is subjected to synaptic plasticity and a prominent monoaminergic influence. However, little is known about the muscarinic cholinergic effects on prefrontal synapses. ⋯ Monoamine levels were specifically altered in the mPFC. We observed a decrease in dopamine, 5-HT, 5-hydroxyindolacetic acid and noradrenaline levels, with no changes in 3,4-hydroxyphenylacetic acid levels. Our data, therefore, suggest that muscarinic activation exerts a boosting effect on mPFC synaptic plasticity and possibly on mPFC-dependent memories, associated to monoaminergic changes.
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The beneficial effects of caffeine on cognition are controversial in humans, whereas its benefit in rodents had been well characterized. However, most studies were performed with acute administration of caffeine and the tasks used to evaluate cognition had aversive components. Here, we evaluated adulthood administration of caffeine up to old age on recognition memory in mice using the object recognition task (ORT) and on brain-derived neurotrophic factor (BNDF) and tyrosine kinase receptor (TrkB) immunocontent in the hippocampus. ⋯ Caffeine also counteracted the age-related increase in BDNF and TrkB immunocontent. Our results corroborate with other studies and reinforce that caffeine consumed in adulthood may prevent recognition memory decline with aging. This preventive effect may involve a decrease in the hippocampal BDNF and TrkB immunocontent.
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The mammalian cerebellum is composed of a highly reproducible array of transverse zones, each of which is subdivided into parasagittal stripes. By using a combination of Purkinje cell antigenic markers and afferent tracing, four transverse zones have been identified: the anterior zone (AZ: approximately lobules I-V), the central zone (CZ: approximately lobules VI-VII), the posterior zone (PZ: approximately lobules VIII-dorsal IX) and the nodular zone (NZ: approximately ventral lobule IX+lobule X). Neurofilament-associated antigen (NAA) is an epitope recognized by a monoclonal antibody, which is expressed strongly in association with neurofilaments. ⋯ The novel restriction boundary at lobule VII/VIII, which is also reflected in the morphology of the external granular layer and aligns with a gap in the developing Purkinje cell layer, precedes the morphological appearance of the posterior superior fissure between lobules VIb and VII. In addition, afferent axons to the CZ terminate in an array of parasagittal stripes that is probably a specific climbing fiber projection. Thus, the transverse zone architecture of the mouse cerebellum is more complex than had previously been appreciated.
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Both mu- and delta-opioid agonists selectively inhibit nociception but have little effect on other sensory modalities. Voltage-activated Ca(2+) channels in the primary sensory neurons are important for the regulation of nociceptive transmission. In this study, we determined the effect of delta-opioid agonists on voltage-activated Ca(2+) channel currents (I(Ca)) in small-diameter rat dorsal root ganglion (DRG) neurons that do and do not bind isolectin B(4) (IB(4)). ⋯ Additionally, DPDPE significantly inhibited high voltage-activated I(Ca) in Tyrode's or N-methyl-d-glucamine solution but not in tetraethylammonium solution. This study provides new information that delta-opioid agonists have a distinct effect on voltage-activated Ca(2+) channels in different phenotypes of primary sensory neurons. High voltage-activated Ca(2+) channels are more sensitive to inhibition by delta-opioid agonists in IB(4)-negative than IB(4)-positive neurons, and this opioid effect is restricted to DRG neurons devoid of functional T-type Ca(2+) currents.