Inhibition of mast cell degranulation decreased the number of lever presses (i.e., sign-tracking behavior), but not the number of magazine entries (i.e., goal-tracking behavior), during late stages of PCA training (Sessions 4–5) when PCA behavior fully expresses and rats are normally characterized. Cromolyn (n = 6), a mast cell inhibitor, or saline vehicle (n = 7) was infused (i.c.v.) immediately before each PCA training session. Data are presented as mean and S.E.M. ** - p < 0.01.