Studying scared rats can reveal secrets of human health

Holly Herman

Some people go to haunted houses to experience fear for fun, but UT researchers are using fear in a different way. 

Daniel Johnston, UT neuroscience professor and director of the Center for Learning and Memory, has been inducing fear in rats to prove the link between major depressive disorder and epilepsy.

Different psychological studies have found that depression and fear-induced anxiety often occur together. One study by John Tiller of the University of Melbourne found that 85 percent of patients with major depressive disorder were also diagnosed with generalized anxiety disorder, and 35 percent had symptoms of panic disorder.

Johnston said he and the researchers in his lab have been interested in epilepsy for many years and only recently began using rats in this way. 

“We can make a rat have epilepsy, and we can also make a model for depression by making the rat have some of the symptoms of major depressive disorder,” Johnston said.

Giving a rat depression-like symptoms is done by placing it in stressful situations, such as a near-drowning experience. Once the rat has depression-like symptoms, Johnston and his team measure the electricity in the rat’s neurons to determine where signals might be blocked from reaching the ion channels in the brain that help regulate emotions and memory. 

The results of the experiment are embedded in the electrical activity of neurons caused by proteins in ion channels. The membranes of single neurons conduct electricity, which is conducted by common ions found in salts. 

“We’ve discovered an ion channel in particular that has a common defect in both epilepsy and depression,” he said.

“It’s well-known that there’s a strong [correlation] between epilepsy and depression, so what I mean by that is that patients who have very severe depression are more likely to have epilepsy,” said Johnston. “But it’s not known as well if there’s any underlying neurobiological mechanisms that are similar in the two diseases.”

Scientists often study animal models, such as rats and mice, to research different medical conditions and diseases. 

“It’s hard to study a disease unless there are animal models,” Johnston said. “It’s been one of the problems with some of the psychiatric disorders. Concerning the ethics of using rats, I would say that it’s much more preferable to use them in place of humans.”

Johnston said he hopes his research is something that will interest people inside and outside the field of neuroscience. He said being able to test the effects of major depressive disorders and anxiety, and how the two overlap in causing epilepsy, is important because it may lead scientists to better target treatments for one or both of the diseases.

“A lot of people are very frustrated as to why we can’t solve diseases more quickly than we do,” Johnson said. “The problem is that biology, in particular neurobiology, is very complicated — we don’t have answers to a lot of questions unless there are people like basic scientists, myself and many others, doing research to try and answer some of these questions.”