The Hidden Roles of Dopamine and Serotonin: Scientists Solve Monoamine Mystery

Pictured is an optical section of planarian testes, showing mRNAs expressed at different stages of spermatogenesis, including early spermatogonia (magenta) and spermatocytes (yellow-to-red). DNA staining (cyan) highlights changes in testis cell nuclei throughout spermatogenesis. Melanie Issigonis et al. found that the enzyme AADC in reproductive niche cells helps the enzyme NRPS produce the dipeptide β-alanyl-tryptamine (BATT). Inhibition of the gene for either enzyme in planarians led to the loss of female reproductive organs and accumulation of spermatogonial stem cells in testes. The defects were reversed by administering synthetic BATT. According to the authors, monoamine-derived compounds, such as BATT, can trigger development in reproductive niche cells. Credit: Melanie Issigonis, Katherine Browder, and Phillip Newmark, Morgridge Institute for Research

Researchers have discovered a new role for biogenic monoamines, such as dopamine and serotonin, in the reproductive development of planarian flatworms, suggesting these neurotransmitters also serve as critical signaling molecules beyond brain functions in various species.

Biogenic monoamines, such as dopamine and serotonin, are well-known for their functions in the brain as regulators of mood, learning and memory, stress responses, and the body’s fight-or-flight reactions.

But these neurotransmitters existed in nature long before brains popped up in the evolutionary tree. They’re prevalent in plants, bacteria, and single-cell organisms as well, but their functions there are far less understood.