By Stacy Pitcairn
Neuroscience labs don’t often look like mad science labs. Typically, you see graduate students analyzing data on computers, postdoctoral fellows pipetting at the bench, or conducting various other mundane laboratory tasks. Some days, though, it feels like you’ve stepped into the lab of Dr. Frankenstein himself. Picture it—a brain removed from the skull, sliced and kept alive in a bubbling beaker over a heated bath. This is what the lab looks like when a scientist is doing patch clamp electrophysiology, a technique that is used to study how neurons communicate with each other. In addiction research, this method is used to explore cutting-edge questions about how drugs and alcohol affect the brain. Researchers at Wake Forest School of Medicine have recently examined the effects of alcohol on a largely unexplored region of the brain that could be a treatment target for alcohol use disorder (Bach et al., 2021). But how does this technique work to uncover potential treatment targets?
Often, neurobiological techniques require brain tissue that has been frozen or “fixed” with chemicals that stiffen the gelatinous brain... Electrophysiology, on the other hand, observes the living neuron in real time.
Often, neurobiological techniques require brain tissue that has been frozen or “fixed” with chemicals that stiffen the gelatinous brain. The neurons themselves are long dead, but scientists get a snapshot of what the brain looked like while it was alive. Electrophysiology, on the other hand, observes the living neuron in real time. Neurons communicate through electrical signals. Similar to Morse code, the message is embedded within the pattern of the electrical signals, where one neuron is the sender of the message and another neuron is the receiver. Electrophysiologists work as a sort of “wire tapper” that can listen in on the conversations between these neurons and see what type of message is being sent.
For example, neurons can either activate a neuron they’re connected to, or they can inhibit their partner neuron. These “go” or “stop” messages are expressed through patterns that look distinctly different on the recording equipment. Scientists who study the effects of alcohol on the brain often want to examine how alcohol changes these messages. But neurons need to be alive in order to see that in real time. That’s where the mad science comes in.
To study how alcohol changes the brain, you need boozy brains. This is done using rodents, some of which have had alcohol exposure. Another set of rodents make up the control group — experiencing the same experimental events but without alcohol. Following alcohol exposure, brain tissue is collected and immediately placed into solutions that keep it alive—no bolt of lightning required! One of these is a solution of salts that electrophysiologists mix up to mimic naturally-occurring cerebrospinal fluid, a clear fluid that surrounds our brains and spinal cords. Large metal gas canisters connect to tubing that runs into the fluid and bubbles oxygen and carbon dioxide into the bath. Then, the brain is sliced into thin sections, and placed onto an electrophysiology setup, called a rig, in a bath of artificial cerebrospinal fluid that continues to be bubbled with oxygen. Now, the neurons are ready to be recorded from.
Figure 1. A typical rig includes a microscope and camera in order to magnify the neurons. A tiny electrode is moved using a device called a micromanipulator that allows the researcher to move in microscopic distances. Through extensive training, the electrophysiologist can create a seal between the electrode and the membrane of the neuron. Then, they add suction that ruptures the neuronal membrane, allowing for electrical current to flow from the inside of the neuron to the electrode. The changes recorded by the electrode can be observed on a computer screen.
A study led by Dr. Eva Bach at Wake Forest School of Medicine used this technique to see what the electrical message looks like between a group of rats that received alcohol and a control group. By doing this, they can get a picture of how alcohol exposure could lead to distortions of this electrical message. They recorded electrical current from neurons in two connected brain regions that are involved with negative emotions related to alcohol withdrawal, such as anxiety. They found that the normal balance between excitation (“go messages”) and inhibition (“stop messages”) in these regions was disrupted in rats that received chronic alcohol (Bach et al., 2021). This disrupted balance led the neurons in one of the regions to be “hyperexcitable”, meaning that it is more likely that the neurons will activate, similar to an itchy trigger finger. They also found that withdrawal from chronic alcohol strengthens the connection between these brain regions. Given that activity in this connection promotes anxiety, and chronic alcohol strengthens it, this finding indicates that the neurons here could be a potential treatment target for anxiety associated with alcohol withdrawal.
They recorded electrical current from neurons in two connected brain regions that are involved with negative emotions related to alcohol withdrawal, such as anxiety
Other researchers have used this technique to examine the effects of different drugs, such as opioids, on brain regions involved in substance use disorders. One study from the lab of Dr. Marvin Diaz at Binghamton University used electrophysiology to uncover what occurs in the hippocampus, a brain region involved in memory, in fetal rats that are exposed to the opioid methadone during gestation. When they recorded from a specific type of hippocampal neuron, they saw that female rats who had been prenatally exposed to methadone had greater inhibition (“stop messages”) and decreased excitability (“go messages”) compared to controls (Gamble et al., 2022). In addition to changes in the neuronal firing, they also saw that these females performed worse on a memory task than the rats who had no methadone exposure (Gamble et al., 2022). By understanding how the neurons are communicating with each other, researchers are better able to understand what happens in the brain as a result of drug and alcohol exposure and develop better treatment approaches for people with substance use disorders.
Despite using a technique that seems straight out of classic science fiction movies, electrophysiologists are not mad scientists. Their research provides understanding of which brain regions may be involved in various disorders and that could respond to new treatments. Although it appears that they study the “living dead”, the recorded neurons start to die off by the end of the work day. The results of their work, however, can go on to benefit real, living human patients.
Written by Stacy Pitcairn
Illustrated by Nadia Penkofflidbeck
Edited by Paige Nicklas, Daniel Janko, and Zoë Dobler
Bach, E. C., Ewin, S. E., Baldassaro, A. D., Carlson, H. N., & Weiner, J. L. (2021). Chronic intermittent ethanol promotes ventral subiculum hyperexcitability via increases in extrinsic basolateral amygdala input and local network activity. Scientific Reports, 11(1), 8749. https://doi.org/10.1038/s41598-021-87899-0
Gamble, M. E., Marfatia, R., & Diaz, M. R. (2022). Prenatal methadone exposure leads to long-term memory impairments and disruptions of dentate granule cell function in a sex-dependent manner. Addiction Biology, 27(5), e13215. https://doi.org/10.1111/adb.13215