Neuroscience
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The cortical regions surrounding the suprasylvian sulcus have previously been associated with motion processing. Of the six areas originally described by Palmer et al. [J Comp Neurol 177 (1978) 237], the posteromedial lateral suprasylvian (PMLS) cortex has attracted the greatest attention. Very little physiological information is available concerning other suprasylvian visual areas, and in particular, the anteromedial lateral suprasylvian cortex (AMLS). ⋯ Finally, 45% of 20 neurons were direction selective to a radial optic flow stimulus. Overall, these results suggest that AMLS cortex is involved in higher-order analyses of visual motion. It is possible that the AMLS cortex represents a region between PMLS and the anterior ectosylvian visual area in a functional hierarchy of areas involved in motion integration.
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Comparative Study
Increased expression of Ca2+/calmodulin-dependent protein kinase II alpha during chronic morphine exposure.
The chronic administration of morphine and related opioid drugs results in tolerance and dependence which limits the clinical utility of these agents. Neuronal plasticity is probably responsible in large part for tolerance and dependence. Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) plays a crucial role in the neuroplastic events underlying memory formation and other phenomena. ⋯ In addition, the abundance of phosphorylated CaMKIIalpha was increased in spinal cord tissue from morphine-treated mice. We conclude that enhanced CaMKIIalpha expression and activity in spinal cord tissue may contribute to the development of morphine tolerance in mice. The involvement of this enzyme in opioid tolerance suggests other parallels may exist between the neuroplastic events related to memory formation and those related to opioid tolerance or pain.
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Comparative Study
Urocortin expression in the Edinger-Westphal nucleus is down-regulated in transgenic mice over-expressing neuronal corticotropin-releasing factor.
In recent years a large body of evidence has emerged linking chronic stress with increased vulnerability for depression and anxiety disorders. As corticotropin-releasing factor (CRF) is hypersecreted under these psychological conditions, we used our CRF-overexpressing (CRF-OE) mouse line to study underlying brain mechanisms possibly causing these disorders. Urocortin (Ucn), a recently discovered member of the CRF peptide family may play a role in the pathophysiology of stress-induced disorders. ⋯ Our results support this hypothesis as we found weaker immunohistochemical labeling with anti-Ucn and a six times weaker Ucn mRNA signal in E-WN in CRF-OE mice. Moreover, E-WN Ucn-expressing neurons mounted a response to acute challenge in CRF-OE mice too. From these results it is concluded that the CRF and E-WN Ucn neuronal systems work in concert in response to acute challenges, but are inversely regulated in their activities during chronic hyperactivity of the hypothalamo-pituitary-adrenal axis.
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Gap junctions between glial cells in mammalian CNS are known to contain several connexins (Cx), including Cx26, Cx30 and Cx43 at astrocyte-to-astrocyte junctions, and Cx29 and Cx32 on the oligodendrocyte side of astrocyte-to-oligodendrocyte junctions. Recent reports indicating that oligodendrocytes also express Cx47 prompted the present studies of Cx47 localization and relationships to other glial connexins in mouse CNS. In view of the increasing number of connexins reported to interact directly with the scaffolding protein zonula occludens-1 (ZO-1), we investigated ZO-1 expression and Cx47/ZO-1 interaction capabilities in brain, spinal cord and Cx47-transfected HeLa cells. ⋯ ZO-1 was found to co-immunoprecipitate with Cx47, and pull-down assays indicated binding of Cx47 to the second PDZ domain of ZO-1. Our results indicate widespread expression of Cx47 by oligodendrocytes, but with a distribution pattern in relative levels inverse to the abundance of Cx29 in myelin and paucity of Cx29 in oligodendrocyte somata. Further, our findings suggest a scaffolding and/or regulatory role of ZO-1 at the oligodendrocyte side of astrocyte-to-oligodendrocyte gap junctions.
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Although gender differences in the response to stress have been reported, differences in stress-induced changes in feeding behavior have not been well studied. In this report, inhibition of food intake was compared in male and female rats following 1 h of restraint, electric footshock, or emotional stress induced by a communication box. Although the three stressors inhibited food intake in both genders, only emotional stress caused a gender difference, a greater inhibition of food intake in female rats (48%) than in male rats (22%). ⋯ Ovariectomy reduced the inhibition of food intake by emotional stress to the same level as that in male, and replacement with estradiol restored the inhibition to the level of the normal female rats. A corticotropin-releasing factor (CRF) type 1 receptor antagonist prevented emotional stress-induced inhibition of food intake, indicating the involvement of CRF type 1 receptor in emotional stress-induced inhibition of food intake. These results suggest that female rats show a greater inhibition of food intake in response to emotional stress than male rats and that estrogen plays a role in the gender difference.