Serotonin is one of the chemical messengers that nerve cells in the brain use to communicate. Modifying serotonin levels is one way that antidepressant and anti-anxiety medications are thought to work and help people feel better. But the precise nature of serotonin’s role in the brain is largely unknown.
That’s why Anne Andrews set out in the mid-1990s as a fellow at NIH’s National Institute of Mental Health to explore changes in serotonin levels in the brains of anxious mice. But she quickly realized it wasn’t possible. The tools available for measuring serotonin—and most other neurochemicals in the brain—couldn’t offer the needed precision to conduct her studies.
Instead of giving up, Andrews did something about it. In the late 1990s, she began formulating an idea for a neural probe to make direct and precise measurements of brain chemistry. Her progress was initially slow, partly because the probe she envisioned was technologically ahead of its time. Now at the University of California, Los Angeles (UCLA) more than 15 years later, she’s nearly there. Buoyed by recent scientific breakthroughs, the right team to get the job done, and the support of a 2017 NIH Director’s Transformative Research Award, Andrews expects to have the first fully functional devices ready within the next two years.
Neurotransmitters are often present in extremely low concentrations in the spaces outside of neurons, where communication takes place. That has made designing a neural probe sensitive enough to detect them with the needed specificity a huge challenge. Andrews’ team—including Milan Stojanović, Columbia University, New York City, along with UCLA’s Paul Weiss, Harold Monbouquette, and Yang Yang—found a solution in molecules known as aptamers. They are single stranded nucleic acids that are selected for their unique ability to bind a chemical structure of interest.
Andrews’ team now has aptamers that recognize a number of essential nerve messengers, including serotonin and dopamine, with many more in development. Andrews reports that these aptamers are selective and sensitive enough to differentiate between chemicals that are very similar in structure.