Figure 6

Octopamine and dopamine receptor antagonists impair appetitive and aversive second-order conditioning. (A-C) Three groups of animals were each injected with 3 μl of saline containing 1 μM epinastine at 30 min before the first conditioning stage (A), before the second conditioning stage (B), or before the final test (C) in appetitive second-order conditioning. One control group received no injection (B, intact), and two other groups were each injected with saline at 30 min before the second conditioning stage (B, saline), or before the final test (C, saline). (D-F) Three groups were each injected with 3 μl of saline containing 500 μM fluphenazine at 30 min before the first conditioning stage (D), before the second conditioning stage (E), or before the final test (F) in aversive second-order conditioning. Animals received four first-stage trials and then four second-stage trials for appetitive second-order conditioning, and six first-stage trials and then four second-stage trials for aversive second-order conditioning. One control group received no injection (E, intact), and two other groups were each injected with saline at 30 min before the second conditioning stage (E, saline) or before the final test (F, saline). Preference indexes for the CS2 (in the case of appetitive second-order conditioning) or the control pattern (in the case of aversive second-order conditioning) before (white bars) and after (black bars) conditioning are shown with means + SEM. The results of statistical comparison are shown as asterisks (* P < 0.05; ** P < 0.01; *** P < 0.001; NS P > 0.05).