Neuroscience
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Noninvasive neural imaging has become an important tool in both applied and theoretical applications. The hemodynamic properties that are measured in functional magnetic resonance imaging (fMRI), for example, are generally used to infer neuronal characteristics. In an attempt to provide empirical data to connect the hemodynamic measurements with neural function, we have conducted previous studies in which neural activity and tissue oxygen metabolic functions are determined together in co-localized regions of the central visual pathway. ⋯ In this investigation we have used several specific spatial stimulus patterns presented to either the CRF or the surrounding region or to both areas together in order to determine spatial response patterns. Within the CRF, we find that neural and metabolic responses sum in a nonlinear fashion but changes in these two measurements are closely coupled. For stimuli that extend beyond the CRF, neural activity is generally reduced while oxygen response exhibits uncoupled changes.
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Peripherally restricted analgesics are desirable to avoid central nervous system (CNS) side effects of opioids. Nonsteroidal anti-inflammatory drugs produce peripheral analgesia but have significant toxicity. GABA(B) receptors represent peripheral targets for analgesia but selective GABA(B) agonists like baclofen cross the blood-brain barrier. ⋯ In a mouse model of osteoarthritis, isovaline restored performance during forced exercise to baseline values. Immunohistochemical staining of cutaneous layers of the analgesic test site demonstrated co-localization of GABA(B1) and GABA(B2) receptor subunits on fine nerve endings and keratinocytes. Isovaline represents a new class of peripherally restricted analgesics without CNS effects, mediated by cutaneous GABA(B) receptors.
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Although short-term synaptic plasticity (STP) is ubiquitous in neocortical synapses its functional role in neural computations is not well understood. Critical to elucidating the function of STP will be to understand how STP itself changes with development and experience. Previous studies have reported developmental changes in STP using acute slices. ⋯ Importantly, despite the change in the PPR we did not observe changes in the time constant governing STP. Since these experiments were conducted in vitro our results indicate that the shift in STP does not depend on in vivo sensory experience. Although sensory experience may shape STP, we suggest that developmental shifts in STP are at least in part ontogenetically determined.
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It is well known that after cerebral ischemia, brain suffers blood flow changes over time that have been correlated with inflammation, angiogenesis and functional recovery processes. Nevertheless, post-ischemic spatiotemporal changes of brain perfusion have not been fully investigated to date. Here we tested whether PET with [¹³N]ammonia would evidence the perfusion changes presented by different brain regions in an experimental model of brain ischemia. ⋯ [¹³N]ammonia shows hemodynamic changes after stroke involving hyperperfusion that might be related to angiogenesis and functional recovery. Long-term blood hyperperfusion is found both in ischemic and remote areas to infarction. These results may contribute to a better understanding of the evolution of cerebral ischemic lesion in animal models.
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Intermittent social defeat stress exposure augments behavioral response to psychostimulants in a process termed cross-sensitization. Brain-derived neurotrophic factor (BDNF) mediates synaptic plasticity and cellular responses to stress and drugs of abuse. We previously showed that repeated social defeat stress persistently alters BDNF and activates ΔFosB expression in mesocorticolimbic regions. ⋯ Stress exposure increased BDNF immunoreactivity in anterior cingulate, prelimbic and infralimbic regions of the prefrontal cortex (PFC), medial amygdala (AMY), nucleus accumbens (NAc) and VTA; ΔFosB labeling in anterior cingulate cortex (ACG) and nucleus accumbens; and ΔFosB/BDNF co-expression in prelimbic cortex (PL), nucleus accumbens and medial amygdala. Infralimbic ΔFosB-labeling was enhanced by stress in neurons innervating the VTA. Increased ΔFosB/BDNF co-expression and persistent functional activation of corticolimbic neurons after stress may contribute to mechanisms underlying cross-sensitization to psychostimulants.