The dopaminergic system of Caenorhabditis elegans

Dopamine is a highly conserved neurotransmitter that plays a pivotal role in regulating a wide array of behaviours. In vertebrates, it is best known for its involvement in motor control, motivation, reward processing and learning. Dysregulation of dopaminergic signalling is implicated in several human neurological and psychiatric disorders, most notably Parkinson's disease. The fundamental importance of dopamine has driven researchers to study it across a range of model organisms. Among these, the nematode Caenorhabditis elegans has proven particularly valuable. With a compact and fully mapped nervous system, genetic tractability and transparent body, C. elegans provides a powerful system to unravel the mechanisms of dopamine synthesis, signalling, receptor function and behavioural modulation. Like in mammals, dopamine is produced by a small number of neurons, yet it governs complex behaviours including locomotion, learning and responses to environmental cues. In this review, we explore the breadth of research on dopaminergic signalling in C. elegans, focusing on its synthesis, receptor signalling and downstream effects on behaviour. By integrating findings across molecular, cellular and circuit levels, we aim to highlight both the conserved features of dopamine signalling and the unique insights gained from studying it in this model organism.