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Background:Binge drinking is common in adolescents, but the impact of only a few binges on learning and memory appears underestimated. Many studies have tested the effects of long and intermittent ethanol exposure on long-term synaptic potentiation, and whether long-term synaptic depression is affected remains unknown.Methods:We studied the effects of one (3g/kg, i.p.; blood ethanol content of 197.5±19mg/dL) or 2 alcohol intoxications (given 9 hours apart) on adolescent rat’s memory and synaptic plasticity in hippocampus slice after different delay.Results:Animals treated with 2 ethanol intoxications 48 hours before training phase in the novel object recognition task failed during test phase. As learning is related to NMDA-dependent mechanisms, we tested ketamine and found the same effect as ethanol, whereas D-serine prevented learning deficit. In hippocampus slice, NMDA-dependent long-term synaptic depression was abolished 48 hours after ethanol or ketamine but prevented after D-serine or in a low-Mg2+ recording medium. Long-term synaptic depression abolition was not observed 8 days after treatment. An i.p. treatment with MK-801, tetrahydroisoxazolopyridine, or muscimol was ineffective, and long-term synaptic potentiation, intrinsic excitability, and glutamate release remained unaffected. The input/ouput curve for NMDA-fEPSPs was shifted to the left 48 hours after the binges with a stronger contribution of GluN2B subunit, leading to a leftward shift of the Bienenstock-Cooper-Munro relationship. Interestingly, there were no cellular effects after only one ethanol injection.Conclusion:Two ethanol “binges” in adolescent rats are sufficient to reversibly abolish long-term synaptic depression and to evoke cognitive deficits via a short-lasting, repeated blockade of NMDA receptors only, inducing a change in the receptor subunit composition. Furthermore, ethanol effects developed over a 48-hour period of abstinence, indicating an important role of intermittence during a repeated long-duration binge behavior.

Ciliary neurotrophic factor (CNTF) is a potent neuroprotective cytokine in different animal models of glutamate-induced excitotoxicity, although its action mechanisms are still poorly characterized. We tested the hypothesis that an increased function of glial glutamate transporters (GTs) could underlie CNTF-mediated neuroprotection. We show that neuronal loss induced by in vivo striatal injection of the excitotoxin quinolinic acid (QA) was significantly reduced (by ∼75%) in CNTF-treated animals. In striatal slices, acute QA application dramatically inhibited corticostriatal field potentials (FPs), whose recovery was significantly higher in CNTF rats compared to controls (∼40% vs. ∼7%), confirming an enhanced resistance to excitotoxicity. The GT inhibitor dl-threo-β-benzyloxyaspartate greatly reduced FP recovery in CNTF rats, supporting the role of GT in CNTF-mediated neuroprotection. Whole-cell patch-clamp recordings from striatal medium spiny neurons showed no alteration of basic properties of striatal glutamatergic transmission in CNTF animals, but the increased effect of a low-affinity competitive glutamate receptor antagonist (γ-d-glutamylglycine) also suggested an enhanced GT function. These data strongly support our hypothesis that CNTF is neuroprotective via an increased function of glial GTs, and further confirms the therapeutic potential of CNTF for the clinical treatment of progressive neurodegenerative diseases involving glutamate overflow.