Itching and pain are sensations that are difficult to coexist with each other; when you feel a strong pain, the sensation of itching decreases, but when you feel a strong itch, the sensation of pain decreases. However, little is known about the neural control mechanisms in the brain that influence the interaction between itch and pain.

　In this research, we used an optogenetic method that can manipulate the activity of specific nerve cells in the brain and acute itch/pain model mice to demonstrate that orexin-producing neurons (orexin neurons) in the hypothalamus suppress pain It was revealed that the nerves control these two sensations in opposite directions, on the one hand, and on the other hand, on the other hand, promote itching.

　Orexin neurons were known to be responsible for a variety of functions by projecting from the hypothalamus to various areas of the brain and forming neural circuits. The current study found that the neural circuit that projects from the hypothalamus to the aqueductal gray matter is particularly important for the reciprocal control of itch and pain.

　Furthermore, through experiments using a mouse model of chronic itch that reflects the pathological itch seen in clinical practice, we revealed that orexin nerves also contribute to the deterioration of the pathological condition of chronic itch. These results suggest that hypothalamic orexin neurons may become a new target for the development of treatments for chronic pruritus.

　This research has clarified part of the neural control mechanism that is responsible for answering the question of why itching and pain have a mysterious interaction that cancels each other out. It is hoped that this will lead to research and development of new analgesics and antipruritics from a new perspective.

Paper information:[Communications Biology] Orexin neurons play contrasting roles in itch and pain neural processing via projecting to the periaqueductal gray