Downregulation of the dopamine D2-like receptor in corpus allatum affects juvenile hormone synthesis in Drosophila melanogaster females

In Drosophila, juvenile hormone (JH) is synthesized de novo in the specialized endocrine gland, corpus allatum (CA). Dopamine (DA) controls JH levels by either stimulating or inhibiting its synthesis and degradation depending on the developmental stage. The present study focuses on the role of D2-like receptors in the regulation of JH synthesis by dopamine. We show that D2-like receptors (DD2R) are expressed in CA cells of Drosophila melanogaster females. In addition, the level of JH production was analyzed in D. melanogaster females with decreased DD2R expression in CA (vs. corresponding control flies) by assessing multiple indices of JH synthesis (JH-hydrolyzing activity and stress reactivity of the system of JH metabolism, activity and stress reactivity of the alkaline phosphatase, activity and stress reactivity of the tyrosine decarboxylase). The differential value obtained for each index suggests increased JH production in female flies that downregulate DD2R. Based on these findings, we postulate that the DA inhibiting effect on the JH synthesis in D. melanogaster is mediated at least in part via D2-like receptors.