Modulation of Different Salinity Conditions on Transcriptional Signature of Metabotropic Serotonin and Dopamine Receptors in Nile Tilapia (Oreochromis niloticus)

Abstract

As freshwater resources become increasingly limited, exploiting brackish and marine waters for aquaculture is viewed as a promising alternative. Nile tilapia (Oreochromis niloticus), although considered euryhaline, shows relatively restricted tolerance to salinity compared with other tilapia species, making it an ideal model to study adaptive responses to osmotic stress. Serotonin (5-HT) and dopamine (DA) are key modulators of stress responses through their activation of metabotropic G protein-coupled receptors (GPCRs). In this study, we investigated the transcriptional profiles of metabotropic serotonin and dopamine receptors across the brain, intestine, and liver of Nile tilapia reared in different salinity conditions (0 ppt, 16 ppt, 30 ppt). The results showed both dopamine and serotonin metabotropic receptors were duplicated with potential neofunctionalization, contributing to osmoregulatory capacity. Nile tilapia showed altered brain drd1, htr1 and htr7 subtypes in response to salt change. Meanwhile, the drd3 subtype showed pronounced alterations in the intestine and liver under elevated salinity. Notable transcriptional alterations in htr4 subtypes were observed in both brain and liver, suggesting their potential involvement in modulating energy balance and stress adaptation. Correlation network analyses further demonstrated coordinated regulation among receptor paralogues in the brain. These findings provide potential targets, such as ligand analog additives or genetic enhancement, for future functional validation and for improving salinity tolerance in Nile tilapia culture.

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