On May 5, Beijing time, according to foreign media reports, hugging, holding hands and caressing help us maintain a healthy psychology and are crucial to the healthy development of emotions, but we didn't know why we get spiritual pleasure from such a touch before At present, researchers have found that there is a neural pathway in the brain of experimental mice, which can transmit the feeling called "pleasant touch" from the skin to the brain
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The results of this mouse based experiment help scientists better understand and treat diseases characterized by avoiding contact and damaging the development of human society, including autism spectrum disorders.
"Pleasant touch" is very important for all mammals. Raising a baby is also a way for parents to give the baby a sense of security through touching. Holding the hand of a dying person is also a very powerful and comforting force. Monkeys and other animals comb each other's hair. Human hugging and shaking hands will give each other a pleasant sense of closeness, massage Therapy can reduce pain and stress and is very beneficial to patients with mental illness.
A key neuropeptide and an inherent neural pathway that produces pleasure were found in mouse experiments. In addition to neural pathways, the researchers found that this neuropeptide, prokinecticin 2 (prok2), can transmit the feeling of "pleasant touch". It is reported that neuropeptide is a chemical messenger that transmits signals between nerve cells.
The team found that when they fed mice without prok2 neuropeptide, they did not perceive pleasant touch signals, but still responded normally to itching and other stimuli. Now that it is known which neuropeptides and receptors only transmit pleasant touch sensation, it is possible to enhance the touch signal of pleasant sensation without interfering with other neural pathways. This conclusion is crucial because pleasant touch can promote the brain to produce several hormones, which is essential for social and mental health.
In addition, the team found that experimental rats lacking neuropeptide prok2 (in the case of artificial interference) avoided touch behaviors such as combing their peers' hair and showed signs of stress that other normal mice did not have.
At the same time, the researchers found that compared with mice whose pleasant touch response was blocked in adulthood, mice lacking pleasant touch at birth had severe stress response and showed more group communication avoidance behavior. The findings show that maternal touch is important for the development of offspring. Female rats like to lick their newborn mice. Adult mice often comb their peers' hair. This very normal behavior is helpful for emotional connection, sleep and stress relief. However, rats lacking neuropeptide prok2 in their body will deliberately avoid this behavior. Even if their peers in the cage try to comb their hair, they will try their best to break free, He is very lonely and likes to be alone.
One of the challenges of this study is to figure out how to allow mice to be touched and whether they are touched to produce a sense of pleasure. If an animal doesn't know you, it usually avoids any touch behavior because it will think it is a threat. Our experimental task is difficult. It is a designed experiment to help animals get rid of their instinctive avoidance of touch.
In order to let the mice successfully complete the experiment, the researchers separated the experimental mice from their companions in the cage for a period of time, and then found that the experimental mice prefer to be stroked by a soft brush, just as pets are stroked and groomed.
After several days of hair grooming, the experimental mouse was placed in an environment with two compartments. In one compartment, it was often groomed, and the other compartment did not have any touch stimulation. When it was allowed to choose again after experiencing such compartment life, it would take the initiative to choose the compartment that was often groomed.
Next, the researchers began to identify neuropeptides stimulated by pleasant touch behavior. They found that neuropeptide prok2 in sensory neurons and Prokr2, a receptor expressed in spinal cord neural pathway, transmit pleasant touch signals to brain tissue.
In subsequent experiments, they found that the neuropeptide prok2 was not involved in transmitting other sensory signals, such as itching stimulation. At present, it is the first time to find that the pain and itch stimulation signal is transmitted to the brain through a "special channel", which is different from the transmission of pleasant touch feeling. This latest research report was published in the recently published journal Science.