Neuropharmacological Properties of Pelargonium roseum, Possible Involvement of 5-HT_1A Serotonin Receptor Subtypes

Pelargonium roseum (Geraniaceae) is locally named “GoleAtr”and because of a strong pleasant rose-like scent is widely grown as ornamental plant. Several bioactivities including analgesic, antioxidant and anti-inflammatory effects were attributed to P.roseum. The present study aimed to evaluate neuropharmacological properties of P. roseumessential oil and the possible mechanism of action in murine animal model. Essential oil (EO) was obtained by hydrodistillation from fresh leaves and Gas Chromatography (GC) analysis was performed to reveal chemical constituents of the EO. After acute intraperitoneal treatment with EO at doses of 10, 20 and 40mg/kg behavioral models of open field and elevated plusmaze for investigating anxiolytic activity and forced swimming test for antidepressant activity were utilized. Flumazenil, a competitive antagonist of benzodiazepine binding and the selective5-HT_1A receptor antagonist WAY100635 was used in experimental procedures to determine the action mechanism of EO. GC analysis revealed β- citronellol (35.9%) and geraniol (13.6%) as major component of the EO. EO was effective in increasing the total number of entries and time spent in the open arms of the elevated plus maze while number of crossing and rearing in the open field test were decreased in comparison to control. In the forced swimming test immobility time was decreased in the EO treated mice. The present study found the most effective anxiolytic activity of the EO at the dose of 20mg/ kg (P 0.01). Pretreatment with WAY100635, but not Flumazenil, was able to reverse the effect of the EO in the elevated plus maze, indicating that the EO activity occurs via the 5-HT_1A receptor binding site and serotonergic system but not GABAergic transmission. These results support the use of Pelargonium roseum as a calming agent and suggest the involvement of 5-HT_1A receptors in its anxiolytic activity.