Abstinence from cocaine self-administration promotes microglial pruning of astrocytes, which drives cocaine-seeking behavior.

Rodent drug self-administration leads to a compromised ability of nucleus accumbens astrocytes to maintain glutamate homeostasis as well as to reductions in surface area, volume, and synaptic colocalization of astrocyte membranes. However, the mechanisms driving astrocyte responses to drug administration are unknown. Here, we report that long-access rat cocaine self-administration followed by prolonged home cage abstinence results in decreased branching complexity of nucleus accumbens astrocytes, characterized by the loss of peripheral processes. Using a combination of confocal fluorescence microscopy and immunoelectron microscopy, we show that these alterations in astrocyte structural features are driven by microglial phagocytosis, as virally labeled astrocyte membranes are found within microglial phagolysosomes. Inhibition of complement C3-mediated phagocytosis using the neutrophil inhibitory peptide (NIF) rescued astrocyte structure and decreased cocaine-seeking behavior following cocaine self-administration and abstinence. Collectively, these results provide evidence for microglial pruning of nucleus accumbens astrocytes across cocaine abstinence, which mediates cocaine craving.