Science reveals a new neuroloop DP/DTT-DMH with a faster heartbeat at chronic stress.

We don't know if you have any experience like this. When driving in subject 2 or 3 of driving test, you are nervous, and your back is sweating and your brain is blank. I went through such psychological stress.there are many definitions of psychological stress (also known as psychological stress). In a simple way, in the impending danger (examination, disease, and other events), the mental stress of discomfort will be produced, and various physiological reactions will be triggered. Psychological stress of certain intensity is beneficial to the body, but continuous chronic stress is harmful.in humans, intense and persistent psychological stress usually leads to abnormal sympathetic symptoms such as hyperthermia, increased heart rate and high blood pressure.the dorsal medial hypothalamic nucleus (DMH) plays a key role in stress-induced cardiovascular and neuroendocrine responses, and participates in physiological processes such as thermoregulation, energy consumption, food intake and heart rate.more specifically, DMH neurons expressing bombesin like receptor subtype-3 (BRS-3, a G protein coupled receptor) regulate body temperature, energy consumption and heart rate, while neurons expressing TrkB (tyrosine kinase receptor B) control food intake.in 2014, Kazuhiro, Kyoto University, Japan, also explained the phenomenon of body temperature rise after stress from the level of neural circuit Nakamura's team found that light activated the neural circuit in the raphe medulla (RMR) - dorsal medial hypothalamic nucleus (DMH) can simulate stress-induced temperature rise. In this paper, we revealed that the glutamatergic neural circuit in the raphe medulla is mainly dependent on brown adipose tissue in mediating sympathetic heat production driven by psychological stress.March 6, 2020, based on the above study Kazuhiro Professor Nakamura's research team (now working in the medical department of Nagoya University, Japan) published an article in science magazine and found an important and previously unknown neural circuit: DP / DTT → DMH drives sympathetic and behavioral responses by connecting the subcortical emotional system to the hypothalamic motor control system.researchers used retrograde tracing technology to find mPFC in the upstream brain area of DMH. The medial prefrontal cortex (mPFC) is an important part of limbic system, and its functional and structural abnormalities may be an important cause of depression, anxiety, cognitive impairment, etc.in general, mPFC can be divided into anterior marginal cortex (PRL), inferior border of frontal cortex (IL) and cingulate cortex. However, mPFC was subdivided into PRL, IL, DP (dorsal tegmental cortex) and DTT (dorsal tectal zone). After chronic stress, the number of neurons activated by DMH retrogradely projecting to the four subpopulations of mPFC increased, which indicated that the mPFC → DMH neural loop might be involved in stress response.in the process of selecting the target brain area, the researchers made a trick.there are many studies on the function of PRL and IL, but there are few studies on DP and DTT.based on this consideration, the researchers focused on DP and DTT brain regions. However, due to the small size and close proximity of these two sub regions, it is not easy to distinguish them. Therefore, the overall study here is called DP / DTT.the researchers did find that the central temperature, heart rate and mean arterial pressure of rats after chronic stress were increased, and these sympathetic symptoms disappeared after inhibiting the activity of DP / DTT neurons.by injecting AAV anterograde virus into the DP / DTT brain area, a large number of projection fibers (DP / DTT → DMH) from DP / DTT were observed in the DMH brain area; retrograde tracer dye was injected into the RMR brain area, and neurons from the RMR projection (DMH → RMR) were observed in the DMH brain area, and the axons of DP / DTT → DMH formed excitatory glutamatergic synapses with the projection neurons of DMH → RMR, and then through pharmacology By blocking these synapses, it was found that the sympathetic symptoms induced by chronic stress could be significantly inhibited.in addition, the use of photogenetic techniques to activate DP / DTT → DMH can simulate sympathetic symptoms. These results indicate that the glutamatergic synapses of DMH are involved in the sympathetic symptoms induced by stress.is the DP / DTT → DMH neural loop really so important in the stress-induced body temperature rise? After using CRE dependent specific destruction of DP / DTT → DMH, even under chronic stress conditions, the researchers could not cause body temperature rise and heart rate increase (this technique is very clever, we can learn from it).photoinhibition of this neural circuit produces a similar inhibitory effect.based on this, it is confirmed that the DP / DTT → DMH neural loop plays a key role in the sympathetic symptoms induced by stress from multiple perspectives, and the evidence is sufficient.in the study of neural circuits, we will pay close attention to whether it is related to a specific behavior.in this paper, the chronic stress model adopted by the research team is a kind of social frustration stress model. In a simple way, a strong aggressive Long Evans rat attacks the ordinary rats, and the ordinary rats will show evasive behavior.however, after photoinhibition of the DP / DTT → DMH pathway, the challenged mice did not show evasive behavior.previous research team found that DMH → RMR was involved in stress-induced hyperthermia. In fact, in this study, researchers also found that DMH → RMR pathway needs to be activated when DMH neurons mediate stress-induced sympathetic symptoms.in conclusion, we found that the new loop DMH → RMR regulates the peripheral sympathetic nervous system symptoms caused by chronic stress through virus tracing and immunofluorescence technology, which is helpful to treat such diseases as fear memory and post-traumatic stress disorder.in addition, we found that mPFC in the upstream of DMH and RMR in the downstream brain region previously found can constitute a complete and multi-level neural pathway DP / DTT → DMH → RMR.References: 1. TrkB expressing nerves in the dorsomedial hypothalamus are necessary and sufficient to suppress homeostatic feeding2. GABAergic inputs to POMC nerves originating from the dorsomedial hypothalamus are regulated by energy state3.brs3 nerves in the mouse mesopotalamus regulated body temperature, energy expenditure, and heart rate, but not food intake4.Psychological Stress Activates a Dorsomedial Hypothalamus–Medullary Raphe Circuit Driving Brown Adipose Tissue Thermogenesis and Hyperthermia5.A central master driver of psychosocial stress responses in the rat