Figure 8.

Effects of D2- and D4-specific antagonists on sound sequence discrimination learning. (A) D2 antagonist raclopride (1 mg/kg, i.p.) had a slight but nonsignificant effect on sound sequence discrimination learning. (B) D4 antagonist clozapine (5 mg/kg, i.p.) had a slight but nonsignificant effect. Simultaneous application of raclopride plus clozapine significantly attenuated sound sequence discrimination (*P < 0.05). (C,D,E) Licking behavior was not significantly suppressed by raclopride alone (C), clozapine alone (D), or simultaneous application of both agents (E).