Dopamine (DA) is a key regulator of associative learning and memory in both vertebrates and invertebrates, and it is widely believed that DA plays a key role in aversive conditioning in invertebrates. However, the idea that DA is involved only in aversive conditioning has been challenged in recent studies on the fruit fly (), ants and crabs, suggesting diverse functions of DA modulation on associative plasticity. Here, we present the results of DA modulation in aversive olfactory conditioning with DEET punishment and appetitive olfactory conditioning with sucrose reward in the oriental fruit fly, . Injection of DA receptor antagonist fluphenazine or chlorpromazine into these flies led to impaired aversive learning, but had no effect on the appetitive learning. DA receptor antagonists impaired both aversive and appetitive long-term memory retention. Interestingly, the impairment on appetitive memory was rescued not only by DA but also by octopamine (OA). Blocking the OA receptors also impaired the appetitive memory retention, but this impairment could only be rescued by OA, not by DA. Thus, we conclude that in , OA and DA pathways mediate independently the appetitive and aversive learning, respectively. These two pathways, however, are organized in series in mediating appetitive memory retrieval with DA pathway being at upstream. Thus, OA and DA play dual roles in associative learning and memory retrieval, but their pathways are organized differently in these two cognitive processes - parallel organization for learning acquisition and serial organization for memory retrieval.

中文翻译：

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多巴胺能通路在东方果蝇（橘小实蝇）嗅觉学习和记忆中的双重作用

多巴胺 (DA) 是脊椎动物和无脊椎动物联想学习和记忆的关键调节剂，人们普遍认为 DA 在无脊椎动物的厌恶调节中发挥着关键作用。然而，最近对果蝇、蚂蚁和螃蟹的研究对 DA 只参与厌恶性条件反射的观点提出了挑战，这表明 DA 对联想可塑性的调节具有多种功能。在这里，我们展示了东方果蝇中 DA 在避蚊胺惩罚的厌恶性嗅觉调节和蔗糖奖励的食欲性嗅觉调节中的结果。向这些果蝇注射DA受体拮抗剂氟奋乃静或氯丙嗪会导致厌恶性学习受损，但对食欲性学习没有影响。 DA 受体拮抗剂会损害厌恶性和食欲性长期记忆保留。有趣的是，食欲记忆受损不仅可以通过 DA 来缓解，还可以通过章鱼胺 (OA) 来缓解。阻断 OA 受体也会损害食欲记忆保留，但这种损害只能通过 OA 来挽救，而不能通过 DA 来挽救。因此，我们得出的结论是，OA 和 DA 途径分别独立介导食欲和厌恶学习。然而，这两条途径在介导食欲记忆检索中串联组织，DA 途径位于上游。因此，OA和DA在联想学习和记忆检索中发挥着双重作用，但它们在这两种认知过程中的组织方式不同——学习习得的并行组织和记忆检索的串行组织。