Etude expérimentale des effets d'une consommation modérée d'alcool sur l'altération des fonctions cognitives associée à l'âge (analyse comportementale et neurobiologique chez la souris)

Basé sur les résultats de certaines études épidémiologiques récentes montrant un lien entre une consommation modérée d'alcool et une moindre incidence de l'apparition de démences séniles de type Alzheimer chez le sujet humainvieillissant, notre travail expérimental avait pour principal objectif de comparer chez la souris jeune- adulte et âgée, les effets d'une consommation modérée d'alcool sur les fonctions cognitives et sur certains marqueurs neurobiologiques associés du fonctionnement cérébral. Une première série d'expériences avait pour objectif d'évaluer les performances mnésiques des animaux en utilisant des épreuves permettant de dissocier la mémoire relationnelle/déclarative (affectée par le vieillissement) de la mémoire procédurale (non modifiée). Les résultats obtenus ont essentiellement montré q'une consommation modérée d'alcool produisait un effet bi-directionnel dépendant de l'âge et sélectif de la mémoire relationnelle/déclarative. Plus précisément, l'alcoolisation modérée améliorait la mémoire relationnelle des sujets âgés mais perturbait celle des sujets jeunes-adultes. Chez les sujets âgés, l'alcoolisation produisait également un ralentissement de l'oubli à long-terme.Ces résultats comportementaux nous ont conduit, dans la seconde partie de ce travail, à examiner d'une part si l'expression génique de certains marqueurs neurobiologiques de plasticité synaptique (Neurogranine, Adenylyl cyclase Ca 2+ calmoduline- dépendante, Synaptophysine I et MAP2) était altérée par l'âge et, d'autre part, si la consommation modérée d'alcool prévenait ou atténuait ces altérations. Les résultats obtenus en combinant hybridation in situ et immunohistochimie ont conforté nos données comportementales. Ils montraient en effet que la diminution de l'expression génique de ces marqueurs de plasticité chez l'animal vieillissant était sélectivement rétablie à un niveau présénescent par la consommation modérée d'alcool.La dernière partie de ce travail a été consacrée à une étudefonctionnelled'activation à l'aide de l'imagerie Fos. L'objectif était de déterminer si les modifications âge-dépendantes des performances induites par la consommation d'alcool étaient associées à des modifications d'activation de certains circuits cérébraux lors de la réalisation d'une épreuve d'apprentissage. Les résultats obtenus ont montré que la consommation modérée d'alcool exerce un effet bi-directionnel +-âge-dépendanta sur le fonctionnement du système septo- hippocampique sans modifications notables sur d'autres systèmes (e.g. mamillo-thalamique).Les données obtenues dans le cadre de ce travail représentent les tous premiers résultats expérimentaux plaidant en faveur d'un effet protecteur +-âge- dépendanta d'une consommation modérée d'alcool sur l'altération des fonctions cognitives associée à l'âge.BORDEAUX1-BU Sciences-Talence (335222101) / SudocSudocFranceF

Data from: Pharmacological characterisation of S 47445, a novel positive allosteric modulator of AMPA receptors

S 47445 is a novel positive allosteric modulator of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors (AMPA-PAM). S 47445 enhanced glutamate’s action at AMPA receptors on human and rat receptors and was inactive at NMDA and kainate receptors. Potentiation did not differ among the different AMPA receptors subtypes (GluA1/2/4 flip and flop variants) (EC50 between 2.5–5.4 μM), except a higher EC50 value for GluA4 flop (0.7 μM) and a greater amount of potentiation on GluA1 flop. A low concentration of S 47445 (0.1 μM) decreased receptor response decay time of GluA1flop/GluA2flip AMPA receptors and increased the sensitivity to glutamate. Furthermore, S 47445 (0.1 and 0.3 μM) in presence of repetitive glutamate pulses induced a progressive potentiation of the glutamate-evoked currents from the second pulse of glutamate confirming a rapid-enhancing effect of S 47445 at low concentrations. The potentiating effect of S 47445 (1 μM) was concentration-dependently reversed by the selective AMPA receptor antagonist GYKI52466 demonstrating the selective modulatory effect of S 47445 on AMPA receptors. Using an AMPA-kainate chimera approach, it was confirmed that S 47445 binds to the common binding pocket of AMPA-PAMs. S 47445 did not demonstrate neurotoxic effect against glutamate-mediated excitotoxicity in vitro, in contrast significantly protected rat cortical neurons at 10 μM. S 47445 was shown to improve both episodic and spatial working memory in adult rodents at 0.3 mg/kg, as measured in the natural forgetting condition of object recognition and T-maze tasks. Finally, no deleterious effect on spontaneous locomotion and general behavior was observed up to 1000 mg/kg of S 47445 given acutely in rodents, neither occurrence of convulsion or tremors. Collectively, these results indicate that S 47445 is a potent and selective AMPA-PAM presenting procognitive and potential neuroprotective properties. This drug is currently evaluated in clinical phase 2 studies in Alzheimer’s disease and in Major Depressive Disorder

Pharmacological characterisation of S 47445, a novel positive allosteric modulator of AMPA receptors.

S 47445 is a novel positive allosteric modulator of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors (AMPA-PAM). S 47445 enhanced glutamate's action at AMPA receptors on human and rat receptors and was inactive at NMDA and kainate receptors. Potentiation did not differ among the different AMPA receptors subtypes (GluA1/2/4 flip and flop variants) (EC50 between 2.5-5.4 μM), except a higher EC50 value for GluA4 flop (0.7 μM) and a greater amount of potentiation on GluA1 flop. A low concentration of S 47445 (0.1 μM) decreased receptor response decay time of GluA1flop/GluA2flip AMPA receptors and increased the sensitivity to glutamate. Furthermore, S 47445 (0.1 and 0.3 μM) in presence of repetitive glutamate pulses induced a progressive potentiation of the glutamate-evoked currents from the second pulse of glutamate confirming a rapid-enhancing effect of S 47445 at low concentrations. The potentiating effect of S 47445 (1 μM) was concentration-dependently reversed by the selective AMPA receptor antagonist GYKI52466 demonstrating the selective modulatory effect of S 47445 on AMPA receptors. Using an AMPA-kainate chimera approach, it was confirmed that S 47445 binds to the common binding pocket of AMPA-PAMs. S 47445 did not demonstrate neurotoxic effect against glutamate-mediated excitotoxicity in vitro, in contrast significantly protected rat cortical neurons at 10 μM. S 47445 was shown to improve both episodic and spatial working memory in adult rodents at 0.3 mg/kg, as measured in the natural forgetting condition of object recognition and T-maze tasks. Finally, no deleterious effect on spontaneous locomotion and general behavior was observed up to 1000 mg/kg of S 47445 given acutely in rodents, neither occurrence of convulsion or tremors. Collectively, these results indicate that S 47445 is a potent and selective AMPA-PAM presenting procognitive and potential neuroprotective properties. This drug is currently evaluated in clinical phase 2 studies in Alzheimer's disease and in Major Depressive Disorder

GluA1, GluA2 and GluA4 subunits and splice variants selectivity of S 47445 at human AMPA receptors.

<p>(A) Typical examples of glutamate-evoked currents in absence and presence of 100 μM S 47445 obtained on the same oocyte expressing either GluA1 flip (GluA1i, n = 5) or flop (GluA1o, n = 3) variants. (B) Concentration response curves for S 47445 obtained in oocytes injected with GluA1i and GluA1o receptors. (C) Maximal fold potentiation (E_max) induced by S 47445 on homomeric GluA1 flip (GluA1i), GluA1 flop (GluA1o), GluA4 flip (GluA4i), GluA4 flop (GluA4o) and heteromeric GluA1/GluA2 or GluA4/GluA2 receptors. E_max is given as the amplitude of current evoked in the presence of S 47445 normalized to unity versus the control current evoked by glutamate alone on the same oocytes. n is indicated in brackets. ** p≤0.01 GluA1o versus GluA1i, unpaired T-test. # p≤0.05 GluA1 flop/ GluA2 flip (GluA1o/2i) versus GluA1 flip/ GluA2 flip (GluA1i/2i), Tukey’s test following significant one-way ANOVA performed on GluA1/GluA2 heterodimers. In (A), (B) and (C), cells were held at -80 mV. Values are mean ± SEM.</p

Detailed data of the article

in vitro and in vivo dat

Effects of GYKI52466 attenuates the potentiation caused by S 47445 but not the sensitivity.

<p>Determination of the potentiation caused by a series of S 47445 on the response evoked by 10 μM glutamate conducted in absence or presence of GYKI52466. Typical currents evoked by a 10 μM glutamate test pulse recorded in the same cell are illustrated in the inset. Currents were normalized to unity for the maximal value recorded in presence of 30 μM glutamate alone on the same oocytes (n = 3). Note that exposure to GYKI52466 caused a significant reduction of the magnitude of the potentiation but does not alter the sensitivity to S 47445.</p

EC₅₀, EC_2X and maximal potentiation values obtained with S 47445 and other positive allosteric modulators at rat or human AMPA receptors on oocytes injected with poly(A+) mRNA.

<p>EC₅₀, EC_2X and maximal potentiation values obtained with S 47445 and other positive allosteric modulators at rat or human AMPA receptors on oocytes injected with poly(A+) mRNA.</p

Effects of S 47445 on native rat and human AMPA, NMDA or kainate receptors.

<p>(A) Typical currents evoked by AMPA, kainate or NMDA on oocytes injected with rat cortex or human hippocampal poly(A+) mRNA in absence or presence of 100 μM S 47445 recorded in the same cell. (B) Concentration-activity curves obtained with S 47445 on AMPA-, kainate- or NMDA-evoked current on oocytes injected with rat cortex poly(A+) mRNA (n = 3, 3 and 4, respectively). (C) Comparative effects of S 47445 on AMPA-evoked current on oocytes injected with either human hippocampal or rat cortex poly(A+) mRNA (n = 5 and 3, respectively). In (A), (B) and (C), cells were held at -60 mV. The amplitude of current evoked in the presence of S 47445 was normalized to unity versus the control current evoked by the agonist alone on the same oocytes (either 10 μM AMPA, 1 mM kainate or 300 μM NMDA/30 μM glycine). Results are expressed as mean ± SEM.</p

Effect of S 47445 on spontaneous locomotor activity in rats and mice.

<p>(A) Effect of S 47445 (10, 30 and 100 mg/kg, p.o.) on spontaneous locomotor activity recorded for 30 min, 1 hour after acute administration in Wistar rats (n = 9). Covered distance (cm) was expressed as means + SEM over 3 successive periods of 10 min (0–10, 10–20 and 20–30 min) and overall (0–30 min). Result indicated in brackets represents the percentage of variation as compared to vehicle. (B and C) Effect of S 47445 (10, 30 and 100 mg/kg, p.o.) on spontaneous locomotor activity recorded for 30 min, 1 hour after acute administration in NMRI mice (n = 12). Global activity (B) was expressed as mean ± SEM and number of rearing (C) as median and interquartile range over 6 successive periods of 10 min (0–10, 10–20, 20–30, 30–40, 40–50 and 50–60 min).</p

Effect of S 47445 at chimeric AMPA/kainate receptors.

<p>Typical examples of glutamate-evoked currents in absence and presence of 100 μM S 47445 obtained from the same oocyte expressing either GluA1flop (GluA1o) AMPA R receptors, GluK2 kainate Q editing form receptors or chimeric of AMPA/kainate receptors, GluA1(K2S1) or GluA1(K2NTD). Cells were held at -80 mV.</p