(November 7, 2015) It
used to be enough to call a serotonergic neuron a serotonergic neuron.
These brain cells make the neurotransmitter serotonin, which
helps regulate mood, appetite, breathing rate, body temperature and more.
Recently, however, scientists have begun to learn that these
neurons differ from one another—and that the differences likely matter in
dysfunction and disease.
Last year, a team led by Harvard Medical School genetics
professor Susan Dymecki 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, Dymecki and colleagues have taken a first stab at
systematically characterizing 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.