Paving the way for eating disorder treatments
A team of researchers led by Robarts scientists Vania Prado, PhD, and Marco Prado, PhD, uncovered a new neural mechanism that may explain how our ability to develop habits can contribute to dysfunctional eating.
The study, published in the Journal of Clinical Investigation, demonstrates the essential role of a neurotransmitter called acetylcholine in a part of the brain responsible for habitual behaviour – the striatum.
“The work illustrates how decreased acetylcholine, which also interferes with another important neurochemical known as dopamine, can facilitate the development of habits, leading to changes in eating behaviours in response to stress,” explained Marco Prado.
Researchers found, using touchscreen tests in mice, that changes in acetylcholine in the striatum affect the capacity of mutant mice to change their behaviour in response to changed cues. For example, the mutant mice repeatedly touched the screen with their noses even after they stopped receiving the strawberry milkshake reward, whereas normal mice will only respond when given a reward. Favier then discovered that the mutant mice formed habitual behaviours much faster and easier than normal mice and, surprisingly, these mutant mice were prone to altered eating behaviours, mirroring anorexia and binge-eating patterns observed in humans.
Different parts of the striatum are known to regulate how we acquire habits. When we are set to perform a task, we weigh the benefits with the effort. At first, this requires maximum concentration. When an action is repeated several times, another part of the striatum takes control and this activity becomes automatic. Habits and automation can be good because they make us more efficient and require less effort. However, sometimes habits can take control of our lives and cause problems.
In the study, mutant mice with acetylcholine deficits in the striatum behave and feed normally under non-stressful conditions. On the other hand, when they were under stress, by restricting the amount of food available, they developed different types of maladaptive eating. Depending on the type of stress, the mutant mice would binge eat or, alternatively, reduce the amount of food intake, reproducing some of the features of anorexia. These observations show how the influence of the environment and unbalanced brain chemistry can lead to changes in eating behaviour.
There’s even more good news – researchers also found that low acetylcholine levels can be compensated by administering a drug commonly used for Alzheimer’s disease treatment. This drug leads to improved eating behaviour in the mutant mice. Interestingly, using sophisticated statistical analysis, the researchers found that mice prone to developing more habitual behaviours were more vulnerable to maladaptive eating. They also found that a subgroup of patients with eating disorders seem to have more habitual behaviours as well.
