Conditions related to mental health such as anxiety and depression can negatively alter normal physiological reactions, even resulting in fever. Scientists have discovered a neural pathway that prompts a heat reaction during periods of psychological stress.
Our body’s flight or fight response activates our sympathetic nervous system to initiate physiological reactions to certain situations. Moments of anxiety are interpreted physically as excessive sweating, accelerated heartbeat, and rapid breathing.
In addition to all these changes, your body temperature also rises. According to a study, a similar physiological response can be seen in rodents as well.
Our body stores fatty acids in two forms, white adipose tissue, and brown adipose tissue. Brown fat can be used by the body to generate heat energy. β3-adrenergic receptor proteins are found in large quantities in brown fat, due to which the tissue is able to respond to neurotransmitters and induce hyperthermia.
Researchers introduced viral RNA detectors into the brown adipose tissue in rats, which traveled through nerve cells. This enabled the study to detect regions within the brain that is connected to the fatty cells.
The study led to the finding of an area named rostral medullary raphe (rMR). This area was found to be associated with brown adipose tissue in the rodents. The researchers also went on to pinpoint the dorsomedial hypothalamus (DMH) to be the main brain area leading to the rMR. Artificial stimulation of the DMH-to-rMR pathway resulted in an upsurge in the activity of the neurons leading to the production of heat by the brown adipose tissues.
Surprisingly, artificial stimulation of the DMH-to-rMR simultaneously accelerated heart rate and blood pressure, signifying the role of DMH–rMR in multiple physiological stress responses.
However in humans, physiological response to psychological stress has a more complex pathway, that may need commands from the brain’s cortex known to play a major role in cognition.
The researchers next aimed to locate the regions in the brain cortex that sends specific commands to the DMH. Similar to their study on rodents, the researchers utilized RNA detectors and introduced them into the DMH to find the neurons associated with heat generation. Their study found a single, little-known, area of the cortex to be prominent with the tracers. In order to assess the importance of the cortical area, researchers blocked the connection of this area with the DMH. Blocking of the cortical region resulted in reduced hyperthermia during psychological stress.
According to philosopher and psychologist William James, Fear is an interpretation of physiological responses to threat, instead of the other way around. So considering James is right, fear can be eradicated from rats by simply blocking the physiological responses to a threat.
Apart from mental stresses, physical pain, stage fright, problem anticipation can also result in increased stress-induced heat production through the DP/DTT pathway. Further research employing electrophysiological data recordings of the DP/DTT cells will be essential to understand how varying types of stress affect the DP/DTT pathway and lead to heat production. With continued research, the DP/PTT pathway may hold a cure for chronic psychological conditions including depression and anxiety