Neuroscience
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In semantic categorization processes, individuals form a relation between perceived or imagined objects and knowledge about these objects. In the present semantic categorization study, we correlated endogenous 17-β-estradiol levels (E2) with performance as well as amplitude of theta oscillations in young women (age 23.1±3.4 years). The semantic categorization task consisted of nouns representing either living or non-living items. ⋯ RT, accuracy and post-stimulus theta amplitude were not statistically significantly different among early follicular, late follicular or luteal women. In early follicular but not in late follicular or luteal women, we observed (1) a positive correlation between E2 and latency in RT, (2) a negative correlation between E2 and accuracy, and (3) a negative correlation between E2 and post-stimulus theta amplitude. A mosaic of menstrual cycle phase-dependent and -independent associations may indicate that a similar performance in each menstrual cycle phase is related to different modulation of synaptic activity by hormones.
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Under inflammatory conditions, interleukin-1β (IL-1β) modulates neural stem cells at neurogenic niches. Here we show that spinal cord injury in rats increases IL-1β expression in astrocytes located around the spinal cord ependyma, a region that also holds a neurogenic potential. ⋯ At the time of maximal expression, periependymal upregulation of IL-1β extends beyond 5 mm from the epicenter of the lesion both rostral and caudally. Since IL-1β controls proliferation and cell fate of neural stem/precursor cells, its modulation in periependymal astrocytes might create an appropriate environment for cell replacement after injury.
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Connexin26 (Cx26, GJB2) mutations account for >50% of nonsyndromic hearing loss. The deafness is not always congenital. A large group of these patients (∼30%) demonstrate a late-onset hearing loss, starting in childhood. ⋯ The endocochlear potential was reduced in Cx26 conditional knockout (cKO) mice but the reduction was not associated with progressive hearing loss. These data suggest that Cx26 deficiency may impair active cochlear amplification leading to late-onset hearing loss. Our study also helps develop newer protective and therapeutic interventions to this common nonsyndromic hearing loss.
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Nitric oxide (NO) is a key retrograde messenger that regulates synaptic transmission in the cerebral cortex. However, little is known about NO-induced modulatory effects and their mechanisms relative to inhibitory synaptic transmission. The present study aimed to examine the effects of NO on unitary inhibitory postsynaptic currents (uIPSCs) and to postulate the synaptic location of NO action. ⋯ PPR analysis supports the hypothesis that these SNAP-induced effects are mediated by presynaptic mechanisms in FS→FS/non-FS and non-FS→Pyr/FS/non-FS connections. The NO scavenger, 2-phenyl-4,4,5,5-tetramethylimidazolineoxyl-1-oxyl-3-oxide (PTIO), or the inhibitor of guanylate cyclase, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), abolished the SNAP-induced uIPSC modulation. These results suggest that NO regulation of inhibitory synaptic transmission is dependent on presynaptic cell subtypes and that, at least in part, the effects are mediated by presynaptic mechanisms.
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Extracellular matrix (ECM) accumulates around different neuronal compartments of the central nervous system (CNS) or appears in diffuse reticular form throughout the neuropil. In the adult CNS, the perineuronal net (PNN) surrounds the perikarya and dendrites of various neuron types, whereas the axonal coats are aggregations of ECM around the individual synapses, and the nodal ECM is localized at the nodes of Ranvier. Previous studies in our laboratory demonstrated on rats that the heterogeneous distribution and molecular composition of ECM is associated with the variable cytoarchitecture and hodological organization of the vestibular nuclei and may also be related to their specific functions in gaze and posture control as well as in the compensatory mechanisms following vestibular lesion. ⋯ We have observed positive ECM reaction for the hyaluronan, tenascin-R, hyaluronan and proteoglycan link protein 1 (HAPLN1) and various chondroitin sulfate proteoglycans. The staining intensity and distribution of ECM molecules revealed a number of differences between the functionally different subnuclei of IO. We hypothesized that the different molecular composition and intensity differences of ECM reaction is associated with different control mechanisms of gaze and posture control executed by the visuomotor-vestibular, somatosensory and integrative subnuclei of the IO.