Involvement of substance P/NK1 receptor system in central sensitization in chronic pain.

Chronic pain has become a serious health issue, affecting more than 30% of people worldwide. One of the main mechanisms of chronic pain is central sensitization. It is well known that substance P (SP) and its receptor, Neurokinin 1 receptor (NK1R), play an important role in transmission of nociceptive signals. However, whether SP/NK1R system is involved in central sensitization in chronic pain remains controversial. In the present study, we adopted spared nerve injury (SNI) mouse model to induce neuropathic pain and assessed the role of SP/NK1R system in the development of hyperalgesia and central sensitization. We observed that hyperalgesia occurred in non-injured body part of SNI mice in tail withdrawal test. We also demonstrated hyperexcitability of S1 apical dendrites in SNI mice. Notably, the hyperalgesia behavior and hyperactivity of S1 apical dendrites were alleviated by NK1R antagonist L-703606. These results indicate that SP/NK1R system is involved in central sensitization in chronic pain.