DRD1 and neoplasm: As in the stimulation of Gs-coupled dopamine D1-receptors or Gi-coupled D2-receptors by endogenous dopamine, we investigated whether specific stimulation of dopamine D1-receptor-expressing neurons or inhibition of dopamine D2-receptor-expressing neurons in the nucleus accumbens could produce anti-tumor effects and improve the immune system in transgenic mice using pharmacogenetic techniques.