Figure 2.

The effects of VTA ionotropic glutamate receptor blockade on response rates (a) and glutamate (b) and dopamine (c) levels during a single initial extinction test that followed 2 weeks of self-administration training. Insertion of the response lever was at time=0, marked by the dashed vertical gray lines. Three independent groups were tested: two receiving the ionotropic glutamate receptor blocker kynurenic acid (Kyn: 0.1 or 1.0 mM by reverse dialysis), and one receiving only the Kyn vehicle (aCSF). The response lever was inserted at t=0, indicated by dashed vertical gray lines. Kyn significantly attenuated responding and dopamine but not glutamate levels during extinction.