Abstract

Background Kahweol is a diterpene present in the oil derived from coffee beans. Although several pharmacological activities of kahweol are already well described in the literature, no study was done in order to assess the analgesic activity of this substance. Thus, the aim of this study was to investigate the possible peripheral antinociceptive effect of kahweol. Considering that the opioid peptides have been implicated in peripheral antinociception induced by non-opioidergic compounds, the present study also evaluated the endogenous opioids involvement in this effect.

Methods The rat paw pressure test was used, and hyperalgesia was induced by intraplantar injection of prostaglandin E 2 (2 μg/paw). All drugs were administered subcutaneously in the hindpaws of male Wistar rats. The expression of β-endorphin was examined by immunohistochemistry in the skin tissue samples of the plantar surface of rat right hindpaws.

Results Intraplantar injection of kahweol (40 and 80 μg) induced significant peripheral antinociception. The antinociceptive effect of kahweol was due to a local peripheral action because the higher dose (80 μg/paw) did not produce any effect in the contralateral paw. The opioid receptor antagonist naloxone (50 and 100 μg/paw) prevented action of kahweol (80 μg/paw) and the aminopeptidases inhibitor bestatin (400 μg/paw) potentiated the antinociceptive effect of kahweol (40 μg/paw). Furthermore, kahweol treatment increased the intensity of β-endorphin immunoreactivity in the epithelium of rat paws.