Stress that continues for a long time can really affect how we act. It can make us sad, stop us from having fun with the things we used to enjoy, and in some cases lead to PTSD (a disorder where bad memories stay with you).
Recent scientific research has revealed that stress can make certain cells in the brain very active. These POMC neurons are located in a curved area of the brain, and when they become too active, it causes problems with people’s behaviour. But if we can decrease their activity then this should help to improve peoples’ behaviours.
Scientists from the Medical College of Georgia at Augusta University did some research on how stress affects a certain kind of nerve cells in our brain, called the POMC neurons. To do this experiment, they put animals through 10 days of harsh stress, like restraining them and leaving them alone in wet cages. This was done to see how chronic unpredictable stress impacts these nerve cells.
Researchers examined mice and found that stressful experiences caused the POMC neurons to fire more frequently in males and females. This is according to Dr. Xin-Yun Lu, a Professor at the Neuroscience and Regenerative Medicine Department of MCG who studies neuroscience as part of a special research program.
When scientists directly changed the neurons instead of worrying, it caused people to lose pleasure and show signs of depression. In humans this might look like not hanging out with your close friends or not wanting to do any romantic things. Similarly, when tested in mice, they don’t care in same way for sugar water and male mice don’t get excited by sniffing female urine anymore.
When researchers shut off certain brain cells, it took away this kind of stress-related behaviour for both males and females. This suggests that these POMC neurons are important in order for someone to feel stressed out and to change the way they act because of it. It looks like reducing the amount of inhibitory input on POMC neurons is how a person can become more prone to depression due to stress.
The POMC neurons are located in a special part of the brain called arcuate nucleus (ARC). This area is already known for its involvement with stress-related behaviors.
Nearby the same area, you can also find another group of neurons called AgRP and these are very important when it comes to resilience during stressful conditions or depression. This discovery was reported by a scientist called Lu in Molecular Psychiatry early this year 2021.
Lu’s lab noticed that when people suffer from chronic stress, they start to behave differently – such as becoming less interested in activities, which is called anhedonia. Her team then wanted to research what chronic stress does to neurons called POMC neurons.
AgRP neurons (which help us find food when we’re hungry) have a special relationship with POMC neurons – when AgRP activation increases, the activation of POMC goes down.
When scientists stimulate the AgRP neurons, it can cause us to feel really hungry and make us eat quickly. Also, when we are starving or deprived of food, these same neurons will give off messages telling the POMC neurons to stop blocking our urge to eat.
Research uncovered that continuous stress messes up the balance between two types of brain cells. It appears that having a lot of AgRP (one type of brain cell) interacting with POMC (the other type of brain cell) is really important for their activities, but the main reason why POMC cells are so active during times of chronic stress is because of an intrinsic mechanism in them.
In our bodies, a special kind of neuron called POMC relies on potassium – a type of mineral – to not go too active. Researchers think that stress might affect the movement of potassium and make the neurons fire out-of-control. Therefore, medicines that open up channels for this potassium to move through could be developed in order to control the POMC neurons better.
Sometimes neurons can get overactive and cause seizures. Doctors give medicine called anticonvulsants that open potassium channels up to lower the amount of firing from these neurons. Evidence exists that these medicines might be able to treat depression and anhedonia, which is when you don’t feel happy or excited about the things in your life. The Lu Lab is studying this so we better understand why it works.
Lu hasn’t looked yet, but she wants to study these channels further in order to learn how stress impacts them and POMC neurons. If her research shows that they’re important to the function of these neurons then she wants to be able to target them accordingly.
Stress affects our whole body. Muscles might tense up to protect us from pain and injury. With serious stress, you may have trouble breathing, especially if you already have an illness like asthma. Over time, stress can lead to bigger problems like high blood pressure, heart attack, and stroke. Plus, it can also change the bacteria in our stomach that helps us digest food.
This research was funded by the National Institutes of Health and was written by a group of scientists. The title is “Increased intrinsic and synaptic excitability of hypothalamic POMC neurons underlies chronic stress-induced behavioural deficits”. This study was published in December 2022 and can be found in the journal Molecular Psychiatry with a DOI of 10.1038/s41380-022-01872-5.
