Tissue-specific Serotonin Receptors in Rhodnius prolixus: Potential Roles in Key Vector Processes.

Rhodnius prolixus is a hematophagous insect and the primary vector of Trypanosoma cruzi, the causative agent of Chagas disease. Blood gorging represents an epidemiologically critical event because it is a requirement for development throughout the life cycle and for successful vector reproduction, contributing to population spread. Blood gorging also triggers diuresis, a physiological process that can expel parasites from the hindgut onto the host's skin, thereby facilitating transmission. Serotonin, a biogenic amine, acts through five G-protein-coupled receptors (5-HT1aR, 5-HT1bR, 5-HT2aR, 5-HT2bR, 5-HT7R) to coordinate post-feeding physiological changes in R. prolixus. In this work, serotonin receptor expression was analyzed by re-examining transcriptome data and performing RT-qPCR to evaluate their potential roles in feeding-related physiological events, such as reproduction and diuresis. Thus, in adults, receptor expression was examined in tissues involved in the neuroendocrine and endocrine regulation of reproduction, whereas in fifth instars the focus was on tissues associated with post-prandial diuresis. The expression patterns were tissue-dependent, suggesting that serotonin receptors have tissue-specific functions that vary across developmental stages. Moreover, RNAi experiments provided initial functional insights into serotonin signaling during post-prandial diuresis. Preliminary observations identified 5-HT7R as a potential candidate receptor involved in cuticle plasticization and suggested that compensatory diuretic pathways may help maintain fluid elimination following 5-HT2bR transcript knockdown. Overall, our findings reveal distinct spatial and developmental patterns of serotonin receptor expression, supporting specialized physiological roles for individual receptor subtypes and providing a framework for future studies on the neuroendocrine regulation of feeding-induced processes in R. prolixus.