Figure 4.
Effects of the D1 antagonist SCH 23390 on response induced by the discriminative stimulus for cocaine (S+). SCH 23390 dose-dependently reversed the effects of the S+. For comparison, the figure also shows the average number of responses during the last 3 days of the self-administration (SA) and extinction (EXT) phases, as well as responses in the presence of the stimulus associated with nonreward (S−). *, P < 0.05, significant linear trend over dose levels; +, P < 0.05, different from the EXT and S− conditions; &, P < 0.01, different from cocaine-reinforced responses (SA).