Fear is a natural emotion that people feel when we detect any type of threat. Conditioned fear is what occurs when an individual returns to a situation or environment that has previously caused stress. However, there is also the so-called generalized fear, which arises in the absence of tangible dangers and manifests itself in the form of excessive anxiety, nightmares or uncontrollable thoughts. These symptoms are common among those who have experienced episodes of severe stress and can lead to post-traumatic stress disorder (PTSD).
Neurobiologists from the University of California in San Diego have prepared a study recently published by Science magazine to explain the mechanisms that induce generalized fear. Researchers have identified in mice the changes in brain biochemistry and neural circuits that cause feelings of panic, even when there is no real threat. Likewise, the results of this study open the possibility of using gene therapy to prevent the development of post-traumatic stress disorders.
The research team discovered that episodes of acute stress caused a change in the secretion of neurotransmitters in the midbrain of the mice. Specifically, their neurons stopped releasing glutamate, an exciting substance, to produce GABA, which functions as an inhibitor for the neuronal network. This change induced symptoms of generalized fear in the rodents.
To confirm the hypothesis, when the neurobiologists prevented the segregation of GABA, the mice stopped showing fear. Following this discovery, researchers analyzed post-mortem human brains from people who had been diagnosed with post-traumatic stress disorder. In this way, they observed a similar modification of glutamate by GABA.
The experts also administered fluoxetine, an antidepressant known by the trade name Prozac, after subjecting them to a stressful situation. In this way, the change in neurotransmitter was avoided and, therefore, generalized fear was prevented. Furthermore, the precision at the molecular level of this assay allowed the scientists to observe that the neurons that switched transmitters are connected to regions of the brain that had not previously been linked to the generation of panic responses, namely the central amygdala and hypothalamus. side.
Now that the core mechanism by which generalized fear occurs is known, researchers believe that specific interventions could be carried out among patients who suffer from it. However, further research is needed to determine whether fluoxetine is an effective treatment for people who have had episodes of acute stress.
