Antianxiety effects of a passion flower extract (Passiflora incarnata L.) in animal models of anxiety

Abstract

This study aimed to characterize the putative anxiolytic-like activity of a dried standardised ethanolic extract (PF) prepared from passiflora (Passiflora incarnata L.) using the elevated plus-maze (EPM) and the stress-induced hyperthermia (SIH) mouse models. Male BL6/C57J mice received oral PF or diazepam 1h before behavioral evaluation in the EPM and statistical analysis employed ANOVA with Student-Newman-Keuls post-hoc test. A single oral dose of PF markedly increased the percentage time spent on (p<0.001) and the number of entries (p<0.05) into the open arms of the EPM at a dose of 375mg/kg. The effect was comparable to that of the benzodiazepine diazepam (1.5mg/kg). Emotional- or stress-induced hyperthermia is the rise of body temperature following exposure to psychological stress and occurs across species. Here, exposure to an open field (OF) was the inescapable stressor and significantly increased body temperature (ΔT=1.8±0.13°C, p<0.05) of the mice. SIH is the difference (ΔT=T2-T1) between the basal body temperature (T1) and that after 10min exposure to an OF (T2). Oral PF significantly (p<0.05) reduced ΔT at a dose of 250mg/kg whereas doses of 500 and 125mg/kg) SIH, indicating a U-shaped dose response curve. Additional studies, with EPM, demonstrated that activation of GABA neurotransmission is specifically involved in PF pharmacology and that following chronic treatment with PF similar anxiolytic effects are seen but at lower doses. In conclusion, the selected Passiflora incarnata extract exhibits anxiolytic pharmacological effects in both the EPM and SIH mouse models.