Pharmacological depletion of microglia protects against alcohol-induced corticolimbic neurodegeneration during intoxication in male rats

Excessive alcohol use damages the brain, especially corticolimbic regions such as the hippocampus and rhinal cortices, leading to learning and memory problems. While neuroimmune reactivity is hypothesized to underly alcohol-induced damage, direct evidence of the causative role of microglia, brain-resident immune cells, in this process is lacking. Here, we depleted microglia using PLX5622 (PLX), a CSF1R inhibitor commonly used in mice, but rarely in rats, and assessed cell death following binge-like alcohol exposure in male rats. Eleven days of PLX treatment depleted microglia >90%. Further, PLX treatment prevented alcohol-induced neuronal death in the hippocampus and rhinal cortices, as the number of FluoroJade-B-positive cells (dying neurons) was reduced to control diet levels. This study provides direct evidence that alcohol-induced microglial reactivity is neurotoxic in male rats. Improved understanding of alcohol-microglia interactions is essential for developing therapeutics that suppress pro-cytotoxic and/or amplify protective microglia activity to relieve alcohol-related damage.