Modulation of synaptic plasticity in the cortex needs to understand all the players

The prefrontal cortex (PFC) is involved in cognitive tasks such as working memory, decision making, risk assessment and regulation of attention. These functions performed by the PFC are supposed to rely on rhythmic electrical activity generated by neuronal network oscillations determined by a precise balance between excitation and inhibition balance (E/I balance) resulting from the coordinated activities of recurrent excitation and feedback and feedforward inhibition. Functional alterations in PFC functions have been associated with cognitive deficits in several pathologies such as major depression, anxiety and schizophrenia. These pathological situations are correlated with alterations of different neurotransmitter systems (i.e., serotonin (5-HT), dopamine (DA), acetylcholine...) that result in alterations of the E/I balance. The aim of this review article is to cover the basic aspects of the regulation of the E/I balance as well as to highlight the importance of the complementarity role of several neurotransmitters in the modulation of the plasticity of excitatory and inhibitory synapses. We illustrate our purpose by recent findings that demonstrate that 5-HT and DA cooperate to regulate the plasticity of excitatory and inhibitory synapses targeting layer 5 pyramidal neurons (L5PyNs) of the PFC and to fine tune the E/I balance. Using a method based on the decomposition of the synaptic conductance into its excitatory and inhibitory components, we show that concomitant activation of D1-like receptors (D1Rs) and 5-HT1ARs, through a modulation of NMDA receptors, favors long term potentiation (LTP) of both excitation and inhibition and consequently does not modify the E/I balance. We also demonstrate that activation of D2-receptors requires functional 5-HT1ARs to shift the E-I balance towards more inhibition and to favor long term depression (LTD) of excitatory synapses through the activation of glycogen synthase kinase 3β (GSK3β). This cooperation between different neurotransmitters is particularly relevant in view of pathological situations in which alterations of one neurotransmitter system will also have consequences on the regulation of synaptic efficacy by other neurotransmitters. This opens up new perspectives in the development of therapeutic strategies for the pharmacological treatment of neuronal disorders

Horizons marins, itinéraires spirituels (Ve-XVIIIe siècles). Volume II.

Les 26 contributions réunies dans ce volume renouvellent quelques-uns des secteurs de l'histoire maritime, en attirant l'attention sur la méthodologie, les recherches récentes, les problématiques nouvelles, la recherche interdisciplinaire, l'archéologie, l'iconographie et le roman. On suit pendant deux millénaires quelques-uns des nombreux changements qui ont affecté les façades océaniques des cinq continents, en Amérique latine comme à Madagascar et dans l'Océan Indien, sur les rivages de la Méditerranée comme dans le commerce eurasien. Quelques thèmes demeurent privilégiés, les navires et la navigation, les marines de guerre et les politiques navales des États, l'exploitation des littoraux et les installations portuaires, les marchandises et les frets, les tonnages et les mesures, les assurances maritimes. Les marins, voyageurs, pèlerins, missionnaires, marchands, tous ces gens de mer occupent une grande place dans cet ouvrage, qui traite de la famille, de la formation et des apprentissages, de la santé et des maladies professionnelles, des croyances et des genres de vie. Ce volume qui fait toute sa place à l'histoire des mentalités s'honore de multiples contributions internationales et de la collaboration de quelques spécialistes, médecin, architecte naval..., issus des gens de mer