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Na+/Ca2+ exchangers (NCXs) are mainly expressed in the plasma membrane and exchange one Ca2+ for three Na+, depending on the electrochemical gradients across the plasma membrane. NCXs have three isoforms, NCX1–3, encoded by distinct genes in mammals. Here, we report that heterozygous mice lacking NCX1 (NCX1+/−) exhibit impaired amygdala-dependent cued fear memory. NCX1+/− mice showed significant impairment in fear-related behaviors measured with the elevated-plus maze, light-dark, open-field, and marble-burying tasks. In addition, NCX1+/− mice showed abnormality in cued fear memory but not in contextual fear memory in a fear-conditioning task. In immunohistochemical analyses, NCX1+/− mice had significantly increased number of c-Fos-positive cells in the lateral amygdala (LA) but not in the central amygdala following fear-related tone stimuli. c-Fos expression peaked at 1 h. In concordance with the aberrant fear-related behaviors in NCX1+/− mice, enhanced long-term potentiation was also observed in the LA of these mice. Furthermore, enhancement of CaMKII or CaMKIV activity in the LA was observed in NCX1+/− mice by immunoblot analyses. In contrast, CaMKII+/− but not CaMKIV−/− mice insufficiently exhibited tone-induced cued fear memory and there was no increase in the number of c-Fos-positive cells in the LA. Altogether, the increased CaMKII activity and consequent c-Fos expression likely account for the dysregulation of amygdala-dependent cued fear memory in NCX1+/− mice. [ABSTRACT FROM AUTHOR]

Both reduced nicotinamide adenine dinucleotide phosphate (NADPH) and β-nicotinamide adenine dinucleotide hydrate (NAD+) have been reported to have potent neuroprotective effects against ischemic neuronal injury. Both NADPH and NAD+ are essential cofactors for anti-oxidation and cellular energy metabolism. We investigated if combined NADPH and NAD+ could offer better neuroprotective effects on cellular and animal models of ischemic stroke. In vitro studies with primary cultured neurons demonstrated that NAD+ was effective in protecting neurons against oxygen-glucose deprivation/reoxygenation (OGD/R) injury when given during the early time period of reoxygenation. In vivo studies in mice also suggested that NAD+ was effective for ameliorating ischemic brain damage when administered within 2 h after reperfusion. The combination of NADPH and NAD+ provided not only greater beneficial effects but also larger therapeutic window in both cellular and animal models of stroke. The combination of NADPH and NAD+ significantly increased the levels of adenosine triphosphate (ATP) and reduced the levels of reactive oxygen species (ROS) and oxidative damage of macromolecules. Furthermore, the combined medication significantly reduced long-term mortality, improved the functional recovery, and inhibited signaling pathways involved in apoptosis and necroptosis after ischemic stroke. The present study indicates that the combination of NAD+ and NADPH can produce greater therapeutic effects with smaller dose of NADPH; on the other hand, NADPH can significantly prolong the therapeutic window of NAD+. The current results suggest that the combination of NADPH and NAD+ may provide a novel effective therapy for ischemic stroke. [ABSTRACT FROM AUTHOR]