Antinoceptive effect of triterpenoid alpha,beta-amyrin in rats on orofacial pain induced by formalin and capsaicin.

Abstract

The effects of alpha,beta-amyrin, a pentacyclic triterpene isolated from Protium heptaphylum was investigated on rat model of orofacial pain induced by formalin or capsaicin. Rats were pretreated with alpha,beta-amyrin (10, 30, and 100mg/kg, i.p.), morphine (5mg/kg, s.c.) or vehicle (3% Tween 80), before formalin (20 microl, 1.5%) or capsaicin (20 microl, 1.5 microg) injection into the right vibrissa. In vehicle-treated controls, formalin induced a biphasic nociceptive face-rubbing behavioral response with an early first phase (0-5 min) and a late second phase (10-20 min) appearance, whereas capsaicin produced an immediate face-rubbing (grooming) behavior that was maximal at 10-20 min. Treatment with alpha,beta-amyrin or morphine significantly inhibited the face-rubbing response in both test models. While morphine produced significant antinociception in both phases of formalin test, alpha,beta-amyrin inhibited only the second phase response, more prominently at 30 mg/kg, in a naloxone-sensitive manner. In contrast, alpha,beta-amyrin produced much greater antinociceptive effect at 100mg/kg in the capsaicin test, which was also naloxone-sensitive. These results provide first time evidence to show that alpha,beta-amyrin attenuates orofacial pain at least, in part, through a peripheral opioid mechanism but warrants further detailed study for its utility in painful orofacial pathologies.

• Authors: S A Holanda Pinto, L M S Pinto, M A Guedes, G M A Cunha, M H Chaves, F A Santos, V S Rao
• Journal: Phytomedicine : international journal of phytotherapy and phytopharmacology (Phytomedicine) Vol. 15 Issue 8 Pg. 630-4 (Aug 2008) ISSN: 1618-095X [Electronic] Germany
• PMID: 18164607 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Analgesics
• Formaldehyde
• Oleanolic Acid
• beta-amyrin
• Capsaicin

Topics

• Analgesics (administration & dosage, chemistry, therapeutic use)
• Animals
• Burseraceae (chemistry)
• Capsaicin (toxicity)
• Dose-Response Relationship, Drug
• Drug Administration Schedule
• Facial Pain (chemically induced, prevention & control)
• Formaldehyde (toxicity)
• Male
• Molecular Structure
• Oleanolic Acid (administration & dosage, analogs & derivatives, chemistry, therapeutic use)
• Phytotherapy
• Rats
• Rats, Wistar