Serotonergic neurons make the neurotransmitter serotonin, which helps regulate mood, appetite, breathing rate, body temperature and more.
Previously scientists defined a subgroup of serotonergic neurons in mice by showing that those cells specifically, among all serotonergic neurons, were responsible for increasing the breathing rate when too much carbon dioxide builds up in the body.
Now they systematically characterized serotonergic neurons at the molecular level and defining a full set of subtypes, again in mice.
The researchers report in Neuron that serotonergic neurons come in at least six major molecular subtypes defined by distinct expression patterns of hundreds of genes. In many cases, the subtypes modulate different behaviors in the body.
By conducting a cross-disciplinary series of experiments, the researchers found that the subtypes also vary in their developmental lineage, anatomical distribution, combinations of receptors on the cell surface and electrical firing properties.
The team also showed that a serotonergic neuron's gene expression and function depend not only on its location in the adult brain stem, but also on its cellular ancestor in the developing brain.
While the work was done in mice, authors are optimistic that it will be replicated in humans because the serotonergic neuronal system is in a highly conserved region of the brain, meaning it tends to remain consistent across vertebrate species.