RESUMEN
OBJECTIVES: Copaiba oil oleoresin exuded from Copaifera reticulata Ducke (CRD) is commonly used in anti-inflammatory, healing and anti-tumoral folk medicines. The purpose of this study was to investigate the putative anxiolytic effect of acute administration of CRD. METHODS: CRD was administered (100, 400 and 800 mg/kg, p.o.) to male Wistar rats submitted to the elevated plus-maze model of anxiety using an ethopharmacological analysis. KEY FINDINGS: In comparison with control rats, CRD increased the percentage of entries in the open arms over the entire dose range tested (vehicle, 33.6 +/- 4.5; CRD 100 mg/kg, 44.67 +/- 3.68; CRD 400 mg/kg, 47.2 +/- 2.3; CRD 800 mg/kg, 50.7 +/- 2.2) and the percentage of time spent in the open arms of the elevated plus-maze at the highest dose (800 mg/kg) (vehicle, 26.4 +/- 5.7; CRD 800 mg/kg, 52.0 +/- 2.7). A standard anxiolytic, diazepam (3 mg/kg, p.o.), was used as a positive control. In a similar way, diazepam increased the percentage of entries and time spent in the open arms when compared with vehicle (% open entries: vehicle, 45.4 +/- 1.3; diazepam, 50.7 +/- 1.9; % time spent in open arms: vehicle, 28.2 +/- 0.9; diazepam, 38.9 +/- 1.2). Regarding ethological measures, CRD at the highest dose (800 mg/kg) reduced peeping out (anxiety-related behaviour) (vehicle, 3.1 +/- 0.6; CRD, 0.9 +/- 0.2) and increased end-arm activity (vehicle, 0.2 +/- 0.2; CRD, 2.0 +/- 0.4), indicating an enhanced tendency of the rats to explore actively the potentially dangerous areas of the maze. Diazepam decreased peeping out (vehicle, 3.3 +/- 0.3; diazepam, 1.0 +/- 0.2) and flat-back approach (vehicle, 0.8 +/- 0.2; diazepam, 0.2 +/- 0.1) and increased end-arm activity (vehicle, 0.3 +/- 0.1; diazepam, 2.5 +/- 0.3) and head-dipping (vehicle, 8.2 +/- 0.4; diazepam, 12.0 +/- 0.5). CONCLUSIONS: These data showed, for the first time, that acute treatment with CRD copaiba oil produced a dose-dependent anxiolytic-like effect over the dose range tested, on conventional and ethological parameters, without adversely affecting general activity levels.