As with any disease, vulnerability to addiction differs from person to person. In general, the more environmental and genetic risk factors an individual has, the greater the chance that taking drugs will lead to abuse and addiction. We are interested in determining the role of the following vulnerability factors:
- Identifying the genetic contributions to opioid use disorder. Our lab is using a genetic approach in inbred rats to identify genetic contributions to various opioid-related behaviors, including several aspects directly relevant to the human condition (analgesia, tolerance, acquisition, and escalation of oxycodone self-administration). We are currently performing analyses to determine the inter-relatedness of these measures and calculating an “addiction index” in several inbred rat strains to determine the rat strains that are prone or resistant to the behavioral effects of opioid administration. We will be combining our behavioral findings with existing genomic data to identify genes that are associated with phenotypic variation.
- Assessing how caffeine consumption during adolescence impacts the transition to psychostimulant use (reward, self-administration, and relapse). Our data suggests that adolescent caffeine exposure enhances the stimulant and rewarding properties of cocaine and that these enhancements may be due to caffeine-induced increases in the sensitivity of the dopamine receptors. We are currently exploring the persistent neurobiological changes in the mesocorticolimbic system and the resulting behavioral adaptations that occur from chronic caffeine exposure in adolescents.
- Investigating how dopamine D2 receptor sensitivity may predict addiction vulnerability. Studies show that drug addicts tend to have a reduced availability of dopamine D2 receptors, however, it is unclear whether reduced availability of dopamine D2 receptors is a vulnerability factor or a consequence of repeated drug intake. It was recently suggested that non-abusers with low levels of dopamine D2 receptors report more pleasant experiences when taking drugs of abuse. Thus, dopamine D2 receptor levels and/or sensitivity may predict future drug use. We have been investigating this idea by exploiting individual differences in the behavioral locomotor effects resulting from dopamine D2 receptor stimulation. Early studies suggest that increased dopamine D2 receptor sensitivity predicts enhanced stimulant and rewarding properties of psychostimulants.