Octopamine and dopamine receptor antagonists impair appetitive and aversive olfactory memory recall, respectively. (A, B) Effects of octopamine (OA) (A) or dopamine (DA) (B) receptor antagonists on olfactory memory recall were studied. Twelve groups of animals were each subjected to two-trial appetitive (left) or six-trial aversive (right) olfactory conditioning trials. On the next day, each group was injected with 3 μl of saline or saline containing 1 μM epinastine, 1 μM mianserin, 500 μM fluphenazine, 500 μM chlorpromazine or 500 μM spiperone at 30 min before the final test. Preference indexes for rewarded odor (in the case of appetitive conditioning) or unpunished control odor (in the case of aversive conditioning) before (white bars) and after (black bars) conditioning are shown with means + SEM. The number of animals is shown at each data point in this and in all subsequent Figures. The results of statistical comparison before and after conditioning (Wilcoxon's test) and between experimental and saline-injected control groups (Mann-Whitney test) are shown as asterisks (*P < 0.05; ** P < 0.01; ***P < 0.001; NS P > 0.05).