Dr. Barbara Juarez
Assistant Professor University of Maryland, Baltimore
Postdoctoral Researcher University of Washington
PhD Icahn School of Medicine at Mount Sinai
When Dr. Barbara Juarez was an undergraduate, she did not know what research was, much less that it could be a career. However, an innate sense of curiosity mixed with a touch of serendipity led her to neuroscience research. A biological psychology class at Florida International University (FIU) first inspired an interest in animal behavior and the neural regulation of that behavior. Around the same time, a TA casually mentioned that undergraduates could volunteer in research labs. Barbara looked for neuroscience labs at her university where she might be able to combine her newfound interest in the brain with a budding curiosity about research. There was just one at the time, a lab that focused on neuroanatomy. Barbara began working there, and this was the first in a series of experiences that would culminate in her choosing a career in research and starting her own lab. Today, Barbara is an Assistant Professor at the University of Maryland, Baltimore where her lab studies the neurological basis of substance-use disorders.
As she was nearing the end of her undergraduate studies, Barbara was awarded a spot in FIU’s NIH-funded Minority Biomedical Research Support - Research Training Initiative for Scientific Enhancement (MBRS-RISE) program, which gave her the funding to spend an extra year doing research at FIU after graduating. After this additional year of experience, she applied to postbac programs, ultimately landing a position in the Post-Baccalaureate Research Education Program (PREP) at Icahn School of Medicine at Mount Sinai in New York City. Moving from Florida to New York City was a big transition for Barbara, as was working in a lab associated with a hospital—research at Mount Sinai had a clear translational focus unlike the research she had been doing previously. This emphasis on human health led Barbara to think more about disease states, how they arise, and how they are modulated.
During her two-year postbac in Dr. Ming-Hu Han’s lab at Mount Sinai, Barbara used mouse models to study susceptibility versus resilience to stress and the ways in which brain circuits are altered by stressful experiences. She also began to think about other diseases and their associated brain circuitry. Deciding to stay in the Han lab for a PhD, Barbara shifted her focus from stress to alcohol use disorder. Interestingly, although C57BL/6 mice—an inbred, widely used strain of laboratory mice—tend to exhibit high drinking behaviors when exposed to alcohol, a subset of them appear to be resistant to developing this behavior. In many studies, these “low drinkers” are excluded from experimental cohorts as anomalies, but Barbara wanted to study them and how they might be different from their “high drinker” littermates. Specifically, she wanted to test whether dopaminergic signaling—typically associated with reward-related behavior-—might underlie the individual differences in drinking behaviors. Using electrophysiology to probe neuronal activity, Barbara discovered that, after alcohol exposure, the low drinkers had higher levels of dopaminergic neuronal firing in a region called the ventral tegmental area (VTA). In contrast, the high drinkers exhibited no such increase. She hypothesized that this discrepancy could underlie their different drinking behaviors after alcohol exposure. Remarkably, when Barbara stimulated dopaminergic neurons of high drinking mice to mimic the brain activity of the low drinkers, the mice drank less alcohol. These results highlight the importance of dopamine in determining individual drinking behavior, and this work left Barbara with a persistent interest in the neural correlates of reward-related behavior.
Having become an expert in electrophysiology during graduate school, Barbara was eager to expand her work to include new techniques and approaches. She therefore chose to do her postdoc in Dr. Larry Zweifel’s lab at the University of Washington. The Zweifel lab also focuses on dopamine but from a more molecular angle. Further, they were on the forefront of using CRISPR/Cas9 gene editing technology to probe which specific receptors were important for certain behaviors. Barbara became interested in the balance between phasic firing (when neurons fire many action potentials in a short amount of time) and tonic firing (the baseline level of firing) patterns in dopaminergic neurons. The timing of this transition is important for linking a reward with a certain behavior, and Barbara wanted to better understand how this transition is regulated. Using CRISPR/Cas9 methods to knock out specific ion channel subunits, Barbara found that loss of the potassium channel BKCa1.1 caused an increase in neurons’ phasic, bursting activity and made it harder for them to transition back to tonic firing after presentation of a reward. In contrast, knocking out Kv4.3, a different potassium channel, increased tonic firing. Interestingly, these different firing patterns translated to distinct behaviors. The BKCa1.1 knockout mice could form an association between an action and a reward more quickly, while the Kv4.3 knockout mice were better able to perform a task once they learned it. Together, this work helped to dissect not only how dopaminergic brain circuitry is regulated but also how distinct dopaminergic firing patterns relate to behaviors.
While Barbara’s postdoc was ultimately a fruitful one, it was not without its difficulties. Accustomed to the electrophysiology she had done in graduate school, when she first started her postdoc, Barbara found molecular biology jarring. It felt like molecular techniques revolved around “pipetting clear liquids into clear tubes and just hoping that when you put it into a machine, everything works!” After a string of many failures trying to clone her receptors of interest, Barbara’s project got back on track when a new postdoctoral fellow with extensive cloning experience joined the lab and helped her work through the difficulties. In the end, Barbara not only built up a molecular skillset but also reinforced the power of collaboration. “For me, being able to find colleagues I can do science with has really helped fuel my interest in science and has helped me come up with creative ways to do science.”
Motivated by this love of collaborative science, Barbara started her own lab at the University of Maryland, School of Medicine in Baltimore in 2023. The lab’s mission is to understand how cellular regulators of specific firing patterns in the brain regulate the transition into substance abuse disorders. Currently, she is investigating the role of two different circuits in opioid use disorders, as well as how chronic opioid use affects gene expression. Her lab has recently discovered that a certain cell population in the parabrachial nucleus is activated during opioid withdrawal, and they are hoping that inhibition of these cells might be able to reduce withdrawal symptoms.
As she looks back on her career thus far, Barbara is especially grateful for programs focused on providing research experience and resources to minoritized groups in science. The MBRS-RISE and PREP programs were instrumental in jumpstarting her love for research and helped her feel as if she belonged in research spaces. She also received an NIAAA F31-Diversity fellowship during graduate school and the MOSAIC K99/R00. Now as a PI, Barbara is eager to pay it forward. She is committed to being a mentor for those in training programs like RISE and PREP and to creating DEI programs where they don’t exist. For instance, she recently founded the Promoting Belonging in Neurobiology committee in her department to create an environment that fosters inclusivity and cultural awareness. Undoubtedly, those getting their start in science with Barbara as a mentor, as well as members of the communities she has created, will benefit from having her shining example as inspiration for their own career journeys.
Find out more about Barbara and her lab’s research here.
Listen to Nancy’s full interview with Barbara on April 9, 2024 below!
