Oxysophocarpine induces anti-nociception and increases the expression of GABAAα1 receptors in mice.

Oxysophocarpine (OSC) is an alkaloid extracted from Siphocampylus verticillatus. The aim of this study was to investigate the anti-nociceptive effects of OSC through systemic and intracerebroventricular administration in mice. Moreover, to evaluate its effectiveness and mechanism of action, this study investigated whether OSC altered the expression of γ-aminobutyric acid type A α1 (GABAAα1) receptors in the central nervous system. Thermal and chemical behavioral models of nociception were used to assess the anti‑nociceptive action of OSC. The warm water tail-flick test, the hot‑plate test, acetic acid-induced abdominal constriction and formalin‑induced pain were used in mice. OSC was administered intraperitoneally (i.p.) or intracerebroventricularly (i.c.v.). Results showed that OSC (80 mg/kg, i.p.) significantly increased the tail withdrawal threshold with a peak effect of 25.46% maximal possible effect (MPE) at 60 min (P﹤0.01). Additionally, OSC (80 mg/kg) increased the positive staining of GABAAα1 receptors in cells. In conclusion, OSC administration is suggested to have anti-nociceptive effects on the central and peripheral nervous systems. The involvement of GABAA receptors in the anti-nociceptive activity of OSC is currently being investigated.