Fig 2.

Session blocks of stable remifentanil choice for each choice condition and its reversal in each of three monkeys (CJ82, DJ9J, and R02050). The ordinate represents percent choice for the conditions associated with responding on the left and right levers (solid circles and open circles, respectively). For each monkey, adjacent panels separated by solid lines represent various salvinorin A dose conditions (mg/kg/inj). Hatched lines within these panels represent reversals for the lever response contingencies within each condition. For each reversal within a condition, the lever on which responding results in the delivery of remifentanil (0.1 μg/kg/inj) mixed with salvinorin A is indicated by a “+” sign. Alternatively, the “−” sign indicates that responding on the indicated lever results in an injection of remifentanil alone (0.1 μg/kg/inj). SVA = salvinorin A; L = left lever; R = right lever