Single-Photon-Emission Computed Tomography Studies with Dopamine and Serotonin Transporters in Opioid Users

Opioid dependence is harmful to individuals and society as a whole. Dopamine has been proposed to be involved in the mechanism associated with opioid dependence. Meanwhile, another monoamine neurotransmitter, serotonin, might also play a role. In this chapter, we review the findings from neuroimaging studies that used single-photon-emission computed tomography. In agreement with the dopamine hypothesis of addiction, the findings indicated a 10-30% reduction in dopamine transporter availability among those with opioid dependence. The evidence also implied a certain level of recovery after treatment. A similar effect was also found for serotonin; however, evidence is very scarce. The association between serotonergic activity and treatment outcome is controversial. We discuss the theoretical and clinical implications at the end of this chapter.