Neuroscience
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Maternal thyroid hormones (THs) are important in early brain development long before the onset of embryonic TH secretion, but information about the regulation of TH availability in the brain at these early stages is still limited. We therefore investigated in detail the mRNA distribution pattern of the TH activating type 2 and inactivating type 3 deiodinases (D2 and D3) and the TH transporters, organic anion transporting polypeptide 1c1 (Oatp1c1) and monocarboxylate transporter 8 (Mct8), in chicken embryonic brain as well as in retina and inner ear from day 3 to day 10 of development. Oatp1c1, Mct8 and D3 are expressed in the choroid plexus and its precursors allowing selective uptake of THs at the blood-cerebrospinal fluid-barrier with subsequent inactivation of excess hormone. ⋯ Mct8 is widely expressed in gray matter throughout the brain. This is the first comprehensive study on the dynamic distribution pattern of TH-transporters and deiodinases at stages of embryonic brain development when only maternal THs are available. It provides the essential background for further research aimed at understanding early developmental processes depending on maternal THs.
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Accumulating evidence supports the hypothesis of ecstasy and amphetamine exhibiting neurotoxic properties in human recreational users. The extent and exact location of neuronal degeneration might also be associated with a specific profile of cognitive deterioration described in polydrug users. Voxel-based morphometry and cortical thickness analyses constantly gain attention for answering the question of associated neurological sequelae. ⋯ Our data support the hypothesis that massive recreational amphetamine-type stimulant polydrug use is associated with a thinning of cortical grey matter. Disrupted neuronal integrity in frontal regions does fit well into models of addiction and the cognitive deterioration in amphetamine-type stimulant polydrug users. The exact neurotoxic mechanisms of polydrug ecstasy and amphetamine use, however, remain speculative.
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In this study, we investigated whether two brain regions, the bed nucleus of the stria terminalis (BNST) and the basolateral amygdala (BLA), affected male rats' (Rattus norvigicus) ability to innately discriminate between a predator odor (cat urine) and female rat urine. Muscimol, a GABAa receptor agonist, was bilaterally microinjected into either the BNST or BLA of rats through implanted stainless-steel guide cannulas to temporarily inactivate these brain nuclei. ⋯ Furthermore, intra-BNST infusion of muscimol caused rats to be equally attracted to urine from cats and female rats but intra-BLA infusion did not stop rats manifesting fear on exposure to cat urine and exploratory behavior on exposure to female rat urine. We conclude that the BNST plays a more crucial role in modulating innate fear responses in rats than the BLA.
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Delta opioid receptors participate to the control of chronic pain and emotional responses. Recent data also identified their implication in spatial memory and drug-context associations pointing to a critical role of hippocampal delta receptors. We examined the distribution of delta receptor-expressing cells in the hippocampus using fluorescent knock-in mice that express a functional delta receptor fused at its carboxyterminus with the green fluorescent protein in place of the native receptor. ⋯ Fine mapping in the dorsal hippocampus confirmed that delta opioid receptors are mainly present in GABAergic neurons. Indeed, they are mostly expressed in parvalbumin-immunopositive neurons both in the Ammon's horn and dentate gyrus. These receptors, therefore, most likely participate in the dynamic regulation of hippocampal activity.
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To reveal the fundamental processes underlying the different stages of visual object perception, most studies have manipulated relatively complex images, such as photographs, line drawings of natural objects, or perceptual illusions. Here, rather than starting from complex images and working backward to infer simpler processes, we investigated how the visual system parses and integrates information contained in stimuli of the most basic variety. Simple scatterings of a few points of light were manipulated in terms of their numerosity, spatial extent, and organization, and high-density electrophysiological recordings were made from healthy adults engaged in an unrelated task. ⋯ We were guided in our predictions by the "frame-and-fill" model for object perception, whereby fast inputs to the dorsal stream of the visual "where" system first frame the spatial extent of visual objects, which are subsequently "filled-in" by the slower activation of the ventral stream of the visual "what" system. Our findings were consistent with this view, showing a rapidly-onsetting effect of spatial extent in dorsal stream sources, and later-onsetting effects due to dot number and symmetry, which were deemed to be more closely tied to the details of object identity, from ventral stream sources. This collection of observations provides an important baseline from which to understand the spatio-temporal properties of basic visual object perception, and from which to test dysfunction of this system in clinical populations.