Evidence for a role of 5-HT 1A receptor on antinociceptive action from Geissospermum vellosii

Abstract

Ethnopharmacological relevance Geissospermum vellosii is a tree widely found throughout the Amazonic forest and frequently used by the native population for painful disorders. Aim of the study The present study examined the antinociceptive effects of Geissospermum vellosii in behavioral models of nociception. Materials, methods and results Oral administration of crude extract of Geissospermum vellosii or its dichloromethane fraction (1–100 mg/kg) inhibited formalin-induced inflammatory nociception and acetic acid-induced visceral nociception. The antinociceptive effect of Geissospermum vellosii was unrelated with motor dysfunctions. Furthermore, the alkaloid 12-metoxy-1-methyl-aspidospermidine (0.001–1 mg/kg), isolated from the dichloromethane fraction, also produced antinociception. The antinociception caused by the dichloromethane fraction was significantly attenuated by pre-treatment of mice with p-chlorophenylalanine methyl ester (PCPA, an inhibitor of serotonin synthesis, 100 mg/kg once a day for 4 consecutive days) and WAY-100635 (a 5-HT 1A receptor antagonist, 0.3 mg/kg). In contrast, dichloromethane fraction antinociception was not affected by pre-treatment of animals with ketanserin (a 5-HT 2 receptor antagonist, 0.3 mg/kg) or ondansetron (a 5-HT 3 receptor antagonist, 0.5 mg/kg). Conclusions Together, these results indicate that Geissospermum vellosii produces antinociception through an interaction with 5-HT 1A receptors. Furthermore, the alkaloid 12-metoxy-1-methyl-aspidospermidine contributes to the antinociceptive properties reported for Geissospermum vellosii.