Rehmanniae Radix Preparata (RRP) improves pain sensitization and suppresses PI3K/Akt/TRPV1 signaling pathway in estrogen deficient rats

Abstract

Rehmanniae Radix Preparata (RRP) has been used to management of osteoporotic pain in traditional Chinese medicine trials. However, how RRP exhibits the anti-nociceptive effect remains largely unknown. To this end, estrogen-deficient rats were orally gavaged with aqueous RRP extracts for 12 weeks. The tail flick latency, Von-Frey and formalin assays were employed to evaluate pain sensitization. The administration of RRP alleviates allodynia and hyperalgesia in estrogen-deficient rats. These alterations were associated with a decrease in the expression of substance P (SP), neurokinin-1 receptor (NK-1R), phospho (p)-PI3K, p-protein kinase B (Akt), and transient receptor potential cation channel subfamily V member 1 (TRPV1) in the spinal cord. In addition, RRP improves bone quality in the rats. These results suggest RRP could attenuate pain sensitization and improve bone quality through regulation of PI3K/Akt/TRPV1 signaling pathway during menopause stages. And RRP is considered a novel source of anti-osteoporotic pain drug candidates.

Keywords

• Rehmanniae Radix Preparata
• Estrogen-deficient rats
• Pain sensitivity
• PI3K/Akt/TRPV1
• Bone quality