Harpagophytum procumbens (H. procumbens), also known as Devil's Claw, has been used to treat a wide range of pathological conditions, including
pain,
arthritis and
inflammation. Inflammatory mediators, released at the site of injury, can sensitize nociceptive terminals and are responsible for
allodynia and
hyperalgesia.
Carbon monoxide (CO), produced in a reaction catalyzed by the
enzyme heme oxygenase (HO), may play a role in nociceptive processing and has also been recognized to act as a
neurotransmitter or
neuromodulator in the nervous system. This study was designed to investigate whether the HO/CO pathway is involved in the
analgesic response of H. procumbens in
carrageenan-induced
hyperalgesia in rats.
Mechanical allodynia and
thermal hyperalgesia were evaluated by using von Frey filaments and the plantar test, respectively. The results of our experiments showed that pretreatment with the HO inhibitor
ZnPP IX significantly decreased the antihyperalgesic effect produced by H. procumbens (800 mg/kg, i.p.) in
carrageenan-injected rats. Consistently, the pretreatment with
hemin, a HO-1 substrate, or CORM-3, a CO releasing molecule, before a low dose of H. procumbens (300 mg/kg, i.p.) induced a clear antiallodynic response in
carrageenan injected rats. These results suggest the involvement of HO-1/CO system in the antiallodynic and antihyperalgesic effect of H. procumbens in
carrageenan-induced inflammatory
pain.