Neuroscience
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Atlas of the developing brain of the marmoset monkey constructed using magnetic resonance histology.
The developmental anatomy of the brain is largely directed by neural-based cues. Despite this knowledge, the developmental trajectory of the primate brain has not yet been fully characterized. To realize this goal, the advance in noninvasive imaging methods and new brain atlases are essential. ⋯ The data allowed the generation of a multidimensional atlas of brain structures at different developmental stages. Furthermore, in utero MRI techniques were developed to noninvasively monitor brain development during the embryonic and fetal stages. The multidimensional atlas and the MRI tools developed herein are anticipated to further our understanding of the developing primate brain.
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The aim of this study was to comparatively study cyclin-dependent kinase 5 (CDK5) and c-Fos regulation by morphine in the brains of Lewis and Fischer 344 (F344) rats, which are known to differ in their behavioral sensitivities to several drugs of abuse. Two hours after an acute i.p. administration of morphine (10 mg kg(-1)) or saline (control), the animals were perfused and their brains prepared for immunohistochemistry. The number of CDK5 immunoreactive cells was significantly higher in the nucleus accumbens (NAC), the locus coeruleus (LC) and the nucleus tractus solitarius (NTS) of saline-injected F344 rats than in those of the Lewis rats. ⋯ The effect of the opioid was more marked in the NTS of the Lewis rats and the NAC of the F344 rats. Immunostaining of c-Fos was very low or absent in the control animals and was consistently up-regulated by morphine, especially in the LC and NTS of the F344 rats and the NAC of the Lewis rats. We propose that the acute morphine regulation of CDK5 expression in the NAC may predict the rate of drug intake and/or extinction of drug seeking, while the pattern of c-Fos activation may be more related to the differential acquisition of morphine-seeking behaviors.
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d-Cycloserine (DCS), a co-agonist at the N-methyl-D-aspartate (NMDA) receptor, has proven to be an effective adjunct to cognitive behavioral therapies that utilize extinction. This pharmacological-based enhancement of extinction memory has been primarily demonstrated in neuropsychiatric disorders characterized by pathological fear (e.g. posttraumatic stress disorder and various phobias). More recently, there has been an interest in applying such a strategy in the disorders of appetitive learning (e.g. substance abuse and other addictions), but these studies have generated mixed results. ⋯ Next, we sought to enhance extinction memory using the co-agonist DCS (10 μg/side) by infusion directly into infralimbic medial prefrontal cortex, a brain site implicated in extinction memory recall in conditioned fear models. Indeed, infusion of DCS immediately after the first extinction training session effectively enhanced extinction memory recall 24h later. Collectively, these data suggest that the neurobiological mechanisms and the neurocircuitry mediating extinction memory are similar regardless of the valence (aversive or appetitive) of the conditioned behavior, and that similar pharmacological strategies for treatment may be applied to neuropsychiatric disorders characterized by a failure to inhibit pathological emotional memories.
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The naked mole-rat is a subterranean colonial rodent. In each colony, which can grow to as many as 300 individuals, there is only one female and 1-3 males that are reproductive and socially dominant. The remaining animals are reproductively suppressed subordinates that contribute to colony survival through their cooperative behaviors. ⋯ Animals in both opposite- and same-sex pairs showed a decreased oxytocin neuron number compared to subordinates suggesting that status differences may be due to social condition rather than the reproductive activity of the animal per se. The effects of social status appear to be region specific as no group differences were found for oxytocin neuron number in the supraoptic nucleus. Given that subordinate naked mole-rats are kept reproductively suppressed through antagonism by the queen, we speculate that status differences are due either to oxytocin's anxiolytic properties to combat the stress of this antagonism or to its ability to promote the prosocial behaviors of subordinates.
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Early acoustic experience changes tonal frequency tuning in the inferior colliculus (IC) and the primary auditory cortex. The contributions of IC plasticity to cortical frequency map reorganization are not entirely clear. ⋯ We found that while tone exposure caused a long-lasting increase in cortical representations of the exposure frequency, changes to IC neurons were limited to a transient narrowing of tuning bandwidth. These results suggest that previously documented cortical frequency map reorganization does not depend on similar changes in the subcortical auditory nuclei.