No abstract

Brain energy metabolism actively regulates synaptic transmission and activity. We have previously shown that acute footshock (FS)-stress induces fast and long-lasting functional and morphological changes at excitatory synapses in prefrontal cortex (PFC). Here, we asked whether FS-stress increased energy metabolism in PFC, and modified related cognitive functions. Using positron emission tomography (PET), we found that FS-stress induced a redistribution of glucose metabolism in the brain, with relative decrease of [18F]FDG uptake in ventro-caudal regions and increase in dorso-rostral ones. Absolute [18F]FDG uptake was inversely correlated with serum corticosterone. Increased specific hexokinase activity was also measured in purified PFC synaptosomes (but not in total extract) of FS-stressed rats, which positively correlated with 2-Deoxy [3H] glucose uptake by synaptosomes. In line with increased synaptic energy demand, using an electron microscopy-based stereological approach, we found that acute stress induced a redistribution of mitochondria at excitatory synapses, together with an increase in their volume. The fast functional and metabolic activation of PFC induced by acute stress, was accompanied by rapid and sustained alterations of working memory performance in delayed response to T-maze test. Taken together, the present data suggest that acute stress increases energy consumption at PFC synaptic terminals and alters working memory.

No abstract

The increasing flow of immigrants into Europe over the last decade has generated a range of considerations in the policy agenda of many receiving countries. One of the main considerations for policymakers and public opinion alike is whether immigrants contribute their 'fair' share to their host country's tax and welfare system. In this paper, we assess the net fiscal impact of intra-EU and extra-EU migration in 27 European Union (EU) Member States. We find that migrants in the EU, on average, contribute more than natives to welfare states. However, when we take an age-specific lifecycle perspective, we find that natives generally show a higher net fiscal contribution than both groups of migrants. Among migrants, extra-EU migrants contribute less than intra-EU migrants. We then use a demographic microsimulation model to project the potential net fiscal impact of migration in the EU into the future. We show that despite the fact that intra-EU migration contributes to reduce the strong negative impact of population ageing, its contribution is not sufficient to offset the negative fiscal consequences.

No abstract