adaptation in D1R versus D2R signaling pathways with repeated drug administration is likely to underlie neuroplastic changes in addiction. Overall in animal studies, the increases in D1R signaling are associated with sensitized responses to drugs, and the decreases in D2R signaling with compulsive drug intake (7, 8). Neuroplastic changes in D1R- and D2R-modulated pathways are driven in part by modification in the expression of AMPA and NMDA receptors in glutamatergic synapses (9).
