Neuroscience
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Hypoxic insults during the perinatal period lead to motor and cognitive impairments that later appear during childhood. In the adult brain, hypoxic events often lead to necrotic neuronal death, depending on the region and intensity of the event. During development an active apoptotic cell death occurs and could be an important variable affecting the hypoxic insult outcome. ⋯ In addition we analyzed the influence of retinal ganglion cells (RGC) in neuronal survival. Transection of RGC fibers at embryonic day (ED) 3 did not induce any change in developmental and HxCD at ED12. In conclusion, our findings demonstrate that a hypoxic insult in the developing brain triggers the same apoptotic pathway as the active developmental death.
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Leptin and somatostatin (SRIF) have opposite effects on food seeking and ingestive behaviors, functions partially regulated by the frontoparietal cortex and hippocampus. Although it is known that the acute suppression of food intake mediated by leptin decreases with time, the counter-regulatory mechanisms remain unclear. Our aims were to analyze the effect of acute central leptin infusion on the SRIF receptor-effector system in these areas and the implication of related intracellular signaling mechanisms in this response. ⋯ These changes in sst2 mRNA levels were concomitant with increased activation of the insulin signaling, c-Jun and cyclic AMP response element-binding protein (CREB); however, activation of signal transducer and activator of transcription 3 was reduced in the cortex and unchanged in the hippocampus and suppressor of cytokine signaling 3 remained unchanged in these areas. In addition, the leptin antagonist L39A/D40A/F41A blocked the leptin-induced changes in SRIF receptors, leptin signaling and CREB activation. In conclusion, increased activation of insulin signaling after leptin infusion is related to acute up-regulation of the SRIF receptor-effector system that may antagonize short-term leptin actions in the rat brain.
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Early blindness results in occipital cortex neurons responding to a wide range of auditory and tactile stimuli. These changes in tuning properties are accompanied by an extensive reorganization of the occipital cortex that includes alterations in anatomical structure, neurochemical and metabolic pathways. ⋯ Here, using (1)H magnetic resonance spectroscopy in nine early blind and normally sighted subjects, we find that early blindness is associated with higher levels of creatine, choline and myo-Inositol and indications of lower levels of GABA within the occipital cortex. These results suggest that the cross-modal responses associated with early blindness may, at least in part, be driven by changes within occipital biochemical pathways.
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The medial perforant path (MPP) and lateral perforant path (LPP) inputs to the hippocampal dentate gyrus form two distinct laminar inputs onto the middle and distal aspects of granule cell dendrites. Previous evidence indicated that paired stimuli reliably produced paired-pulse depression (PPD) in the MPP and paired-pulse facilitation (PPF) in the LPP. Despite this, several years of practical experience in our laboratory questioned the utility of using paired-pulse administration to reliably differentiate the MPP and LPP in vitro. ⋯ PPD was more evident in whole cell voltage clamp recordings but nonetheless was not completely diagnostic as PPD was occasionally observed with LPP stimulation as well. We found the MPP and LPP could be reliably identified using conventional microscopy with hippocampal slices, and that they could be distinguished through the analysis of evoked waveform kinetics. This work refines our knowledge of electrophysiological differences between MPP and LPP projections and will help to facilitate the selective activation of these pathways.
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Pain has sensory-discriminative and emotional-affective dimensions. Recent studies show that the affective component can be assessed with a conditioned place avoidance (CPA) test. We hypothesized that systemic morphine before a post-conditioning test would more potently attenuate the affective aspect compared to the sensory component and that [d-Ala2-N-Me-Phe4, Gly-ol5]-enkephalin (DAMGO), a μ-selective opioid receptor agonist, injected into the central nucleus of the amygdala (CeA) would reduce established CPA. ⋯ I.t. morphine did not inhibit the display of CPA but significantly increased PWL, suppressing hyperalgesia (P<0.05). Intra-CeA DAMGO significantly inhibited the display of CPA compared to saline (P<0.05) but had no effect on PWL. The data demonstrate that morphine attenuates the affective component more powerfully than it does the sensory and suggests that the sensory and the emotional-affective dimensions are underpinned by different mechanisms.