Neuroscience
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The hippocampal formation is involved in navigation, and its neuronal activity exhibits a variety of spatial correlates (e.g., place cells, grid cells). The quantification of the information encoded by spikes has been standard procedure to identify which cells have spatial correlates. For place cells, most of the established metrics derive from Shannon's mutual information (Shannon, 1948), and convey information rate in bits/s or bits/spike (Skaggs et al., 1993, 1996). ⋯ In this work, using simulated and real data, we find that the current information metrics correlate less with the accuracy of spatial decoding than the original mutual information metric. We also find that the top informative cells may differ among metrics, and show a surrogate-based normalization that yields comparable spatial information estimates. Since different information metrics may identify different neuronal populations, we discuss current and alternative definitions of spatially informative cells, which affect the metric choice.
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Selective vulnerability or resilience to mood disorders is related to individual differences or personality. In the present study forced swim test (FST) was used as a tool for division of male rats according to their immobility behavior. The animals were subjected to a chronic unpredictable mild stress (CUS). ⋯ The levels of BDNF ExIX and ExI as well TrkB mRNAs were higher in the hippocampus of HI rats as compared to LI rats. In general, the response of hippocampus to CUS was much more expressed as compared to frontal cortex. Thus, initially different stress coping strategies of rats in the FST (HI, LI) were associated with the development of similar behavioral phenotypes after chronic unpredictable stress; however, these phenotypes were associated with different alterations in neurotrophin systems of the brain.
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The ventral tegmental area (VTA) neuronal population consists of dopaminergic (DAergic) and non-DAergic neurons (mainly GABAergic), the activity of which is intertwined with VTA behavioral functions. Both DAergic and GABAergic neurons in the VTA have been shown to express adrenergic receptors (ARs) and respond to AR stimulation. The aim of the present study was to demonstrate the effects of selective AR agonists on DAergic and non-DAergic neuronal activity in the central and lateral parts of the VTA using in vivo electrophysiological recording combined with microiontophoretic drug application in anaesthetized rats. ⋯ Furthermore, we show that α1-AR activation has contrasting effects on putative DAergic and non-DAergic neurons. We hypothesize that the phenylephrine-induced inhibition of putative DAergic neurons results from activation of GABAergic terminals present at the site of drug application. Such a mechanism is further supported by the observed α1-AR-induced excitation of putative GABAergic VTA neurons.
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Cell-cell communication plays a central role in the guidance of migrating neuronal precursor cells during the development of the cerebral cortex. Endocannabinoids (eCBs) have previously been shown to be one of the central factors regulating neuronal migration. In this study the effects of eCBs on different parameters, expected to affect embryonic cortical neuronal motility have been analyzed in neurosphere-derived neuroblasts using time-lapse microscopy. ⋯ Similar changes occur interfering with the function of the metabotropic glutamate receptor 5 (mGluR5) or its transducer canonical transient receptor potential channel 3 (TRPC3) or the neuregulin receptor ErbB4. Blocking of 2-AG production reverses these effects. The data suggest that eCB-regulated neuronal motility is controlled by mGluR5/TRPC3 activity possibly via NRG/ErbB4 signaling.
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Traumatic brain injuries (TBIs) are a common and costly ongoing public health concern. Injuries that occur during childhood development can have particularly profound and long-lasting effects. One common consequence and potential mediator of negative outcomes of TBI is sleep disruption which occurs in a substantial proportion of TBI patients. ⋯ Sham-injured mice housed in enriched environments exhibited enhanced rapid eye movement (REM) sleep and expression of the REM-promoting peptide pro-melanin-concentrating hormone, an effect that was not apparent in TBI mice housed in enriched environments. Thus, TBI blocked the REM-enhancing effects of EE. This work has important implications for the management and rehabilitation of the TBI patient population.