BEHAVIORAL AND MOLECULAR CONSEQUENCES OF MICROGLIAL Csf3r GENE DELETION

Abstract

Among substance use disorders (SUD), cocaine use disorder (CUD) remains one of the most prevalent in the United States, yet no FDA-approved pharmacotherapy exists. This gap is driven in part by incomplete understanding of the disease's pathophysiology. Recent studies have highlighted neuroimmune signaling as a key factor in cocaine motivation, with granulocyte colony-stimulating factor (G-CSF) shown to be sufficient to drive cocaine-seeking behavior. Given the positive correlation between G-CSF levels and drug intake, further investigation into cell-type specificity was warranted. This work characterized a genetic mouse line using Cre recombinase inducible by an estrogen receptor (CreERT2) to achieve microglial-specific Csf3r knockout. The aims were to establish baseline behavioral and molecular consequences of this knockout to clarify the role of microglial G-CSF signaling in cocaine motivation. Behavioral assessments included locomotor activity, behavioral flexibility, conditioned place preference, and anxiety-like behavior. Molecular analyses examined transcription factors, cytokine production, neuroinflammatory markers, and microglial density. We found that microglial Csf3r knockout does not alter learning capacity, baseline locomotor activity, anxiety-like behavior, or conditioned place preference. Molecularly, Csf3r knockout did not affect microglial density, pro-inflammatory cytokine levels, peripheral serum G-CSF, or cocaine-induced Fosb transcription. These findings suggest that microglial Csf3r signaling alone is not sufficient to modulate cocaine motivation.