We investigated the effect of acute oral treatment with a water-alcohol extract of the inflorescence of Erythrina mulungu (EM, LeguminosaePapilionaceae) (100, 200 and 400 mg/kg) on rats submitted to different anxiety models: the elevated T-maze (for inhibitory avoidance and escape measurements), the light/dark transition, and the cat odor test. These models were selected for their presumed capacity to demonstrate specific subtypes of anxiety disorders as recognized in clinical practice. Treatment with 200 mg/kg EM impaired avoidance latencies (avoidance 1 -200 mg/kg EM: 18 ± 7 s, control group: 40 ± 9 s; avoidance 2 -200 mg/kg EM: 15 ± 4 s, control group: 110.33 ± 38 s) in a way similar to the reference drug diazepam (avoidance 1: 3 ± 0.79 s; avoidance 2: 3 ± 0.76 s), without altering escape. Additionally, the same treatments increased the number of transitions (200 mg/kg EM: 6.33 ± 0.90, diazepam: 10 ± 1.54, control group: 2.78 ± 0.60) between the two compartments and the time spent in the lighted compartment in the light/dark transition model (200 mg/kg EM: 39 ± 7 s; diazepam: 61 ± 9 s; control group: 14 ± 4 s). The dose of 400 mg/kg EM also increased this last measurement (38 ± 8 s). These results were not due to motor alterations since no significant effects were detected in the number of crossings or rearings in the arena. Furthermore, neither EM nor diazepam altered the behavioral responses of rats to a cloth impregnated with cat odor. These observations suggest that EM exerts anxiolytic-like effects on a specific subset of defensive behaviors, particularly those that have been shown to be sensitive to low doses of benzodiazepines.

There are more than 100 known species of Erythrina in the tropics. From those, approximately half have been studied.1) Erythrina plants are known to produce alkaloids, flavonoids, and terpenes.1-3) Several species of Erythrina are used in folk medicine due to their tranquilizer effects.4) Alkaloid fractions from Erythrina americana have been shown to possess anticonvulsant, hypotensive, hypnotic, and analgesic effects.5) The tranquilizer effects of crude alkaloid fractions from Erythrina americana were investigated in a model that provokes aggressiveness by visual isolation.4) The alkaloids diminished aggressive behavior in a way similar to the benzodiazepine (BZD) diazepam (DZP), used as a control. Potential therapeutic activity has also been reported for other species of Erythrina. Thus antiviral and antibacterial activity has been shown for Erythrina glauca 3) and Erythrina lysistemon 6) and analgesic and antiinflammatory effects were reported for an aqueous extract from Erythrina senegalensis. 7)Erythrina mulungu (EM) (Leguminosae-Papilionaceae), popularly known as mulungu, is a medium-sized wellbranched tree native to Southern Brazil.8) It produces a profusion of reddish flowers at the end of its branches. Since its flowers are the same color as coral, the plant is sometimes also called "coral tree." In herbal medicine, a leaf or bark decoction or tincture from mulungu is considered to calm agitation and other disorders of the nervous system, including insomnia and depression. 9) As with other species of Erythrina, alkaloids appear to be one of the main constituents of EM. 2)Recently, the supposed therapeutic properties of EM have begun to be evaluated in preclinical studies. Thus, in a previous study performed in our laboratory, 10) the effects of acute treatment with a water-alcohol extract from the inflorescence of EM were investigated in rats submitted to models specifically related to different types of anxiety disorder: the elevated T-maze (ETM), the light/dark transition, and the cat odor test. Results showed that acute treatment with EM altered both inhibitory avoidance latencies in the ETM and the behavior of rats in the light/dark transition model, in a way similar to DZP. Since previous pharmacologic studies pointed to a relationship between these two anxiety-related tasks and generalized anxiety disorder in humans, [11][12][13][14][15][16] these results suggest that acute administration of EM exerts anxiolytic-like effects in a specific subset of defensive behaviors, particularly those related to generalized anxiety.Taking the above evidence into account, the purpose of the present study was to extend the investigation of the anxiolytic potential of EM. It is important to emphasize that in the clinical setting antidepressant compounds have shown therapeutic efficacy in some subtypes of anxiety disorder, i.e., panic, only after chronic treatment.17) Since, aside from its tranquilizer effect, EM has also been popularly used to treat depression, in the present study the effects of repeated administ...

Erythrina velutina (EV) and Erythrina mulungu (EM), popularly used in Brazil as tranquilizing agents, were studied. The effects of acute and chronic oral treatment with a water:alcohol extract of EV (7:3, plant grounded stem bark; acute = 100, 200, 400 mg/kg; chronic = 50, 100, 200 mg/kg) were evaluated in rats (N = 11-12) submitted to the elevated T-maze (for avoidance and escape measurements) model of anxiety. This model was selected for its presumed capacity to elicit specific subtypes of anxiety disorders recognized in clinical practice: avoidance has been related to generalized anxiety and escape to panic. Additionally, animals were treated with the same doses of EV and EM (water:alcohol 7:3, inflorescence extract) and submitted to the forced swim test for the evaluation of antidepressant activity (N = 7-10). Both treatment regimens with EV impaired elevated T-maze avoidance latencies, without altering escape, in a way similar to the reference drug diazepam (avoidance 1, mean ± SEM, acute study: 131.1 ± 45.5 (control), 9.0 ± 3.3 (diazepam), 12.7 ± 2.9 (200 mg/kg), 28.8 ± 15.3 (400 mg/kg); chronic study: 131.7 ± 46.9 (control), 35.8 ± 29.7 (diazepam), 24.4 ± 10.4 (50 mg/kg), 29.7 ± 11.5 (200 mg/kg)). Neither EV nor EM altered measurements performed in the forced swim test, in contrast to the reference drug imipramine that significantly decreased immobility time after chronic treatment. These results were not due to motor alterations since no significant effects were detected in an open field. These observations suggest that EV exerts anxiolytic-like effects on a specific subset of defensive behaviors which have been associated with generalized anxiety disorder.

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