For the first time ever, researchers from the University of Wisconsin-Madison have used stem cells to create specialized nerve cells that produce serotonin, a neurotransmitter in the human brain that among other roles is responsible for mood and appetite regulation.

"Serotonin essentially modulates every aspect of brain function, including movement," Su-Chun Zhang, who headed the research, said in a press release.

Serotonin is created by a small number of localized neurons in the back area of the brain, exerting its broad influence to almost every part of the brain through the neurons that synthesize it.

The researchers began with stem cells derived from embryos and those derived from adult cells. Using these cells, they recreated the chemical environment that is found in the brain as it develops in the uterus.

"That sounds reasonably simple, and we have made so many different types of neural cells," Zhang said. "Here, we had to instruct the stem cells to develop into one specific fate, using a custom-designed sequence of molecules at exact concentrations. That's especially difficult if you consider that the conditions needed to make serotonin neurons are scarce, existing in one small location in the brain during development."

The resulting cells showed expected responses to electrical stimulation and produced serotonin. In addition, they also responded to FDA-approved drugs that regulate anxiety and depression by acting on the serotonin pathway.

The results gained from the study could help in the treatment of psychiatric disorders such as depression.

The findings were published in the Dec. 14 issue of Nature Biotechnology.