As I discussed in this essay last year, the levels of dopamine at D2 receptors may mediate parts of the u-shaped response curve to psycho stimulants. One of the key pieces of evidence for this is that suboptimal baseline activity at D2 receptors in certain brain regions is related to more impulsive responding.
Recently, Lee et al showed that impulsivity, as measured by self-reports (the BIS-11), is negatively correlated with striatal D2/D3 receptor availability as measured by PET. However, the significant correlation was primarily restricted to methamphetamine-dependent individuals (A) as opposed to non-meth-dependent individuals (B), as you can see:
One interesting twist could be to directly test for impulsivity via an individual’s propensity to discount delays in reward and correlate that with striatal D2-receptor like dopamine availability. As Amy Odom (here) discussed today at SQAB, the correlation between self-report and delay discounting isn’t always all that strong.
Lee B et al, 2009. Striatal Dopamine D2/D3 Receptor Availability Is Reduced in Methamphetamine Dependence and Is Linked to Impulsivity. Link here.