Neuroscience
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The capacity to flexibly switch between different task rules has been previously associated with distributed fronto-parietal networks, predominantly in the left hemisphere for phasic switching sub-processes, and in the right hemisphere for more tonic aspects of task-switching, such as rule maintenance and management. It is thus likely that the white matter (WM) connectivity between these regions is critical in sustaining the flexibility required by task-switching. This study examined the relationship between WM microstructure in young adults and task-switching performance in different paradigms: classical shape-color, spatial and grammatical tasks. ⋯ No association was found with behavioral measures obtained in the grammatical task-switching paradigm. The switch costs, a measure of phasic switching processes, were not correlated with WM microstructure in any task. This study shows that a more efficient inter-hemispheric connectivity within the frontal lobes favors sustained task-switching processes, especially with task contexts embedding non-verbal components.
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Kynurenine pathway metabolites (KPM) are thought to be synthesized mainly by non-neuronal cells in the mammalian brain. KPM are of particular interest because several studies demonstrated their implication in various disorders of the nervous system. Among KPM is xanthurenic acid (XA) deriving from the catabolism of 3-hydroxykynurenine. ⋯ Our results also reveal that XA-like immunoreactivity is not expressed by glial cells. To double-check our findings, we have also used another XA antibody obtained from a commercial source to confirm the neuronal expression of XA. Together, our results suggest that, differently to several other KPM produced by glial cells, XA exhibits a neuronal distribution in the mouse brain.
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Amphetamine withdrawal (AW) is accompanied by diminished pleasure and depression which plays a key role in drug relapse and addictive behaviors. There is no efficient treatment for AW-induced depression and underpinning mechanisms were not well determined. Considering both transient receptor potential cation channel, subfamily V, member 1 (TRPV1) and N-Methyl-d-aspartate (NMDA) receptors contribute to pathophysiology of mood and addictive disorders, in this study, we investigated the role of TRPV1 and NMDA receptors in mediating depressive-like behaviors following AW in male mice. ⋯ None of aforementioned treatments had any effect on behavior of control animals. Collectively, our findings showed that activation of TRPV1 and blockade of NMDA receptors produced antidepressant-like effects in male mice following AW, and these receptors are involved in AW-induced depressive-like behaviors. Further, we found that rapid antidepressant-like effects of capsaicin in FST and splash test are partly mediated by NMDA receptors.
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The spinal dorsal horn processes somatosensory information before conveying it to the brain. The neuronal organization of the dorsal horn is still poorly understood, although recent studies have defined several distinct populations among the interneurons, which account for most of its constituent neurons. All primary afferents, and the great majority of neurons in laminae I-III are glutamatergic, and a major factor limiting our understanding of the synaptic circuitry has been the difficulty in identifying glutamatergic synapses with light microscopy. ⋯ We also examined several populations of glutamatergic axons and found that most boutons were in contact with at least one Homer punctum. These results suggest that Homer antibodies can be used to reveal the great majority of glutamatergic synapses without antigen retrieval. This will be of considerable value in tracing synaptic circuits, and also in investigating plasticity of glutamatergic synapses in pain states.
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The bed nucleus of the stria terminalis (BNST), a nucleus defined as part of the extended amygdala, is involved in the expression of anxiety disorders. However, the regulatory mechanisms of BNST inhibitory activity that is involved in anxiety are unknown. Here, we showed that blocking neuregulin 1 (NRG1)-ErbB4 signaling in the BNST of mice, by either neutralizing endogenous NRG1 with ecto-Erbb4 or antagonizing the ErbB4 receptor with its specific inhibitor, produced anxiogenic responses. ⋯ While infusion of the GABAA receptor antagonist bicuculline into the BNST also led to anxiety-related behaviors, it did not worsen the anxiogenic effects produced by blocking NRG1-ErbB4 signaling, suggesting possible involvement of GABAergic neurotransmission. Further, in vitro electrophysiological recordings showed that BNST NRG1-ErbB4 signaling regulated the presynaptic GABA release. Together, these results suggest that NRG1-ErbB4 signaling in the BNST may play an important role in regulating anxiety-like behaviors.