Neuroscience
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Activity-dependent hyperpolarization of EGABA is absent in cutaneous DRG neurons from inflamed rats.
A shift in GABA(A) signaling from inhibition to excitation in primary afferent neurons appears to contribute to the inflammation-induced increase in afferent input to the CNS. An activity-dependent depolarization of the GABA(A) current equilibrium potential (E(GABA)) has been described in CNS neurons which drives a shift in GABA(A) signaling from inhibition to excitation. The purpose of the present study was to determine if such an activity-dependent depolarization of E(GABA) occurs in primary afferents and whether the depolarization is amplified with persistent inflammation. ⋯ The shift in E(GABA) was not blocked by 10 μM bumetanide. Furthermore, because activity-dependent hyperpolarization of E(GABA) was fully manifest in the absence of HCO₃⁻ in the bath solution, this shift was not dependent on a change in HCO₃⁻-Cl⁻ exchanger activity, despite evidence of HCO₃⁻-Cl⁻ exchangers in DRG neurons that may contribute to the establishment of E(GABA) in the presence of HCO₃⁻. While the mechanism underlying the activity-dependent hyperpolarization of E(GABA) has yet to be identified, because this mechanism appears to function as a form of feedback inhibition, facilitating GABA-mediated inhibition of afferent activity, it may serve as a novel target for the treatment of inflammatory pain.
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Exercising during pregnancy has been shown to improve spatial learning and short-term memory, as well as increase brain-derived neurotrophic factor mRNA levels and hippocampal cell survival in juvenile offspring. However, it remains unknown if these effects endure into adulthood. In addition, few studies have considered how maternal exercise can impact cognitive functions that do not rely on the hippocampus. ⋯ The offspring of exercising mothers had more c-FOS expression in the PER than the offspring of non-exercising mothers. By comparison, c-FOS levels in the adjacent auditory cortex did not differ between groups. These results indicate that maternal exercise during pregnancy can improve object recognition memory in adult male offspring and increase c-FOS expression in the PER; suggesting that exercise during the gestational period may enhance brain function of the offspring.
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Light stimulates specialized retinal ganglion cells to release glutamate (Glu) onto circadian clock neurons of the suprachiasmatic nucleus (SCN). Glu resets the phase of the SCN circadian clock by activating N-methyl-d-aspartate receptors (NMDAR) causing either delays or advances in the clock phase, depending on early- or late-night stimulation, respectively. In addition, these Glu-induced phase shifts require tropomyosin receptor kinase B (TrkB) receptor activity. ⋯ TrkB inhibition blocks Cu-induced phase delays but not phase advances. Thus, increasing and decreasing Cu availability appear to shift the SCN clock phase through different mechanisms, at least at the receptor level. We propose that Cu plays a role in the SCN circadian clock by modulating Glu signaling.