The frequency of binge-like ethanol exposure bidirectionally regulates hippocampal mGlu-LTD via synaptic mechanisms and this effect is reversed by minocycline.

Alcohol addiction may begin in young adults through binge drinking (BD) with its frequency as key criterion. In rodents, BD impairs memory and hippocampal synaptic plasticity on the short term and induced neuroinflammation. Memory impairments may persist into adulthood, whereas long-lasting disturbances in hippocampus synaptic plasticity have not been documented. Moreover, the impact of BD frequency on such disturbances and the potential of anti-inflammatory agents to reverse BD-induced alterations remain unclear. Using hippocampal slices from male rats subjected to eight binge-like episodes delivered at high (HF) or low (LF) frequency during adolescence, we found that alterations in group I metabotropic long-term depression (mGlu1/5-LTD) were related to binge-like exposure frequency, with HF reducing mGlu1/5-LTD and intriguingly, LF increasing it. Inhibiting mTORC1 with rapamycin partially corrected LF and HF effects, without alteration of ribosomal protein S6 phosphorylation, a protein downstream of mTORC1, after LF and, a decrease of rp-S6235/236 after HF. Moreover, LF decreased presynaptic GABA vesicular transporter and bicuculline replicated the increased mGlu1/5-LTD after LF. Additionally, N-methyl-D-aspartate receptor-dependent LTD was transiently reduced after HF or LF and rescued with a GluN2B antagonist. Finally, the anti-inflammatory agent, minocycline, administered after the ethanol exposure, reversed all synaptic plasticity alterations. We concluded that bidirectional alteration in mGlu1/5-LTD is a hallmark of ethanol binge exposure frequency, involving pre- and postsynaptic mechanisms. Targeting GluN2B and using anti-inflammatory agents offers promising therapeutic strategies to mitigate the synaptic effects of BD. Our findings highlight the frequency of ethanol exposure as a key determinant of neuronal impact.