In mammals, drugs of abuse, including ethanol, amplify dopaminergic responses to natural rewards and reward-related environmental cues1,14. Consequently, reward-related cues become associated with the reinforcing effects induced by dopamine release in specific brain regions. To test whether activity of dopaminergic neurons was required during acquisition of conditioned preference, we used UAS-shits to impair transmission of TH-expressing neurons with temporal specificity. We shifted the temperature such that neural activity was silenced only during training, when ethanol was presented simultaneously with the odor cue (Fig. 4a). Intriguingly, we found that this manipulation had no effect on the development of conditioned preference (Fig. 4a). This result suggested that dopaminergic neurons might be recruited into the relevant neural circuit during the processes of memory consolidation and/or retrieval. We therefore suppressed neurotransmission in the 24 hrs between training and testing (presumed consolidation phase) or during preference testing (retrieval phase). While activity of dopaminergic neurons during consolidation was dispensable for conditioned preference to form (Fig. 4b), their activity was essential for expression of the memory (Fig. 4c).
