Molecular and pharmacological characterization of the dopamine receptors in the oriental fruit fly, Bactrocera dorsalis

Dopamine (DA) is a critical molecule within the insect nervous system, known to regulate a myriad of physiological functions and instigate behavioral shifts in insects. It exerts its effects by interacting with specific dopamine receptors (DARs). In this study, three DARs cDNAs from Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) (BdDOP1, BdDOP2 and BdDOP3) were cloned using molecular biology techniques. These receptors exhibited high sequence identity with their orthologous DARs, and phylogenetic analyses also clustered these receptors within their respective receptor subtype. Additionally, the high expression levels of these DARs in the head suggest their prominent role in the central nervous system of B. dorsalis. To investigate the pharmacological properties of these receptors, expression vectors for BdDOP1, BdDOP2 and BdDOP3 were constructed and expressed in HEK-293T cells. Our results demonstrated that DA and synthetic agonists activated these receptors in a dose-dependent manner, and DA activation can be competitively inhibited by various antagonists, exhibiting distinct potencies for each dopamine receptor type. Among the tested antagonists, SCH-23390, methiothepin, and metoclopramide were identified as the most potent inhibitors of BdDOP1, BdDOP2 and BdDOP3, respectively. This study provides valuable insights into the molecular and pharmacological characteristics of DARs in B. dorsalis, offering a theoretical foundation for the development of novel behavioral modulators targeting these receptors. The findings also serve as a reference for the functional analyses of DARs in other insect species.