G protein-dependent dopamine D2 receptor signaling mediates cocaine-primed reinstatement.

The high relapse rate of drugs is currently a therapeutic dilemma in the treatment of substance use disorder (SUD). Emerging evidence from preclinical animal models demonstrates that pretreatment with selective dopamine D2 receptor (D2R) antagonists prevents reinstatement of drug-seeking. However, the role of D2R downstream signaling in regulating relapse behavior remains unclear. In this study, we investigated the roles of Gαi-protein- and β-arrestin-dependent D2R signaling pathways in cocaine-primed reinstatement using cocaine self-administration (SA) mouse model treated with biased ligands. We found that treatment of D2R Gαi-protein antagonists, but not β-arrestin antagonists, significantly attenuated cocaine-primed reinstatement of drug seeking without affecting locomotor activity or anxiety levels. Administration of D2R Gαi-protein antagonists, but not β-arrestin antagonists, increased cyclic adenosine monophosphate (cAMP) levels in the nucleus accumbens (NAc). Furthermore, treatment of D2R Gαi-protein antagonists, but not β-arrestin antagonists, suppressed cocaine-induced neuronal activation in the NAc. Our results demonstrate that Gαi-protein-dependent D2R signaling plays a crucial role in cocaine-primed reinstatement and suggest that D2R Gαi-protein-biased ligands may be promising pharmacotherapeutic targets for SUD treatment.