Effects of Phragmanthera capitata (Loranthaceae) on a model of anxiety-like behaviours induced by chronic immobilization stress in mice

This work aims to evaluate the anxiolytic-like effects of Phragmanthera capitata in a model of chronic immobilization stress in mice. Groups of mice were treated in ten consecutive days as follows: a normal control group (NaCl 0.9% per os), a negative control group (chronic immobilization stress + NaCl 0.9% per os), three test groups that were submitted to chronic immobilization stress (CIS) and received three doses of the plant (25, 125, and 250 mg/kg, p.o), and a positive control group (chronic immobilization stress + diazepam 2 mg/kg, i.p). Open field and dark/light tests were used for the evaluation of anxiolytic effects. Antioxidant activities and the involvement of gabaergic neurotransmission were determined by measuring the levels of malondialdehyde (MDA), reduced glutathione (GSH), catalase (CAT), gamma amino butyric acid (GABA), and GABA-transaminase (GABA-T) in the brain. Our results show that the highest dose of Phragmanthera capitata induced a significant increase (p < 0.001) of time spent in the centre, number of crossing and number of grooming in the open field test and a significant increase (p < 0.001) of time spent in the light compartment and the latency of the first escape in the light compartment of the dak/light test. The level of MDA and the activity of GABA-T were significantly decreased by the Phragmanthera capitata while reduced GSH, CAT and GABA, levels were increased. These results suggest that Phragmanthera capitata possesses anxiolytic-like effects that may be supported by its antioxidant activities and or the GABA neurotransmission.