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Scientists discover for the first time the effects of growth hormone on "anxiety neurons" (28 notícias)

Publicado em 10 de janeiro de 2024

Depression, anxiety and post-traumatic stress disorder (PTSD) affect millions of people around the world. Although the exact mechanisms of these diseases are not fully understood, there is growing evidence that hormones may influence a person's susceptibility to these diseases. Researchers have identified specific neurons responsible for controlling how growth hormone affects the production of anxiety and fear memories, a hallmark of post-traumatic stress disorder. The discovery could lead to a new class of anti-anxiety drugs.

A new study by researchers at the University of São Paulo (USP) in Brazil provides a better understanding of the role of a hormone - growth hormone (GH) - in anxiety disorders, identifying for the first time the role of growth hormone in regulating anxiety, Neurons affected by neuropsychiatric disorders such as depression and post-traumatic stress disorder.

José Donato Júnior, corresponding author of the study, said: "We discovered the mechanism of anxiolytic (anxiety-reducing) action of GH, which provides a possible solution for these diseases. There are simply chemical explanations for why patients who secrete more or less GH are more or less likely to develop these diseases."

The somatotropic cells of the pituitary gland secrete adrenocorticotropic hormone, which is mainly controlled by growth hormone-releasing hormone (GHRH), somatostatin (SST) and gastrin. The former is secreted by the hypothalamus to stimulate the release of adrenocorticotropic hormone. The latter is secreted by various tissues throughout the body to inhibit the release of adrenocorticotropic hormone.

Fear-related disorders, such as panic disorder, phobias, and post-traumatic stress disorder, are characterized by pathological fear responses resulting from exposure to intense fear-inducing events, resulting in the formation of "fear memories" in the hippocampus and amygdala . Gastrin plays a role in this.

"The role of gastrin in the post-traumatic stress response has been studied for some time," Donato said. "Studies have shown that under chronic stress, gastrin-induced increases in GH secretion are beneficial to fear memory and memory in the animal brain." The development of post-traumatic stress."

The same goes for SST. Although studies have shown that SST-expressing neurons in the amygdala are associated with changes in anxiety and fear memory, it is currently unknown whether these neurons respond to and mediate the effects of GH in regulating anxiety and fear memory. That's exactly what the researchers wanted to investigate.

They found that in mice, about 60% of SST-expressing neurons in the amygdala responded directly to GH. In adult male and female mice in which the GH receptor gene was knocked out in SST-expressing neurons, male mice showed more anxiety-like behavior, while female mice showed no change in anxiety. In the absence of GH receptors, fear memory was significantly reduced in both male and female mice.

The study did not give a reason for the gender differences.

"We think this may be related to sexual dimorphism," Donato said. "We know that the areas of the brain that contain the neurons we studied are somewhat different in men and women. Some neurological diseases are also different in men and women." , but probably not because of the change."

The findings suggest that anxiety, post-traumatic stress and fear memories are different aspects of the same brain circuit.

"All of this happens in the same population of neurons that express GH receptors," Donato said. "In our experiments, when we turned off GH receptors, the mice had less fear memory. This It means that the ability to form fear memories is impaired. It may be that GH causes the occurrence of post-traumatic stress reaction."

The researchers say the knowledge gained from the study could be used to develop a new class of anti-anxiety drugs. Furthermore, since GH secretion decreases with age, further studies should investigate potential links between GH, SST neurons, and neuropsychiatric disorders during aging. However, the next step for the researchers is to study the role of GH during pregnancy.

"We know that one of the peaks in GH secretion occurs during pregnancy," Donato said. "We also know that the incidence of depression increases during this period due to postpartum depression. Of course, these diseases also reflect social, economic and other aspects of stress, but we cannot forget that increased hormone secretion during pregnancy and postpartum can cause brain dysfunction and lead to these types of mental illnesses.