Neurotropin alleviates rat osteocarcinoma pain via P 2 X 3 receptor activation in the midbrain periaqueductal gray

• Published in: Iranian journal of basic medical sciences 2021-10, Vol.24 (10), p.1395
• Main Authors: Liu, Xingfeng, He, Jingxin, Xiao, Zhi
• Format: Article
• Language: English
• ISSN: 2008-3866

Clinically effective analgesia treatment for patients afflicted with osteocarcinoma lessens the intensity of pain. The midbrain periaqueductal gray (PAG) plays a critical role in pain modulation, and activation of P X receptors in this region mediates pain processing. Neurotropin is a small molecule drug used for analgesic treatment of a number of chronic pain conditions. The present study aims at determining whether P X receptor activation in PAG is responsible for the analgesic effect of neurotropin in rats with osteocarcinoma pain. The tibia of female Sprague-Dawley rats was inoculated with breast carcinoma cells to establish the osteocarcinoma pain model. The effects of intraperitoneal injection of 6, 12, and 18 neurotropin units (NU)/kg on pain threshold and receptor expression of P X in the ventrolateral PAG (vlPAG) were assessed. The P X receptor antagonist A-317491 (1.5 nmol/0.3 µl) was administered into vlPAG with a high-dose neurotropin (18 NU/kg) to determine the role of this receptor in the analgesic effect. The pain thresholds of the rats with osteocarcinoma pain continuously decreased, whereas P X receptor expression in vlPAG only slightly increased after osteocarcinoma cell inoculation. Neurotropin substantially elevated the pain threshold and P X receptor expression in vlPAG in a dose-dependent manner. A-317491 microinjection into vlPAG significantly reduced the analgesic effects of neurotropin in the rats with osteocarcinoma pain. Through these findings, it is shown that vlPAG P X receptor activation participates in neurotropin-mediated analgesia mechanism in osteocarcinoma pain.