Anti-aggressive activity of methyl jasmonate and the probable mechanism of its action in mice.

This study examines the anti-aggressive activity of methyl jasmonate (MJ) and its probable mechanism of action in mice. Male mice that showed aggression after housing individually with female counterparts for 3 weeks or kept in isolation for 4 weeks were treated with MJ, vehicle or haloperidol (HP) 60 min before the test for aggression. Effects of p-chlorophenylalanine (PCPA) or fluoxetine (FL) given alone or in combination with MJ were also investigated. In the interaction studies, PCPA or FL was given to the animals 30 min after MJ injection and aggression testing was carried out 30 min later. Parameters assessed in the study were latency to attack, frequency of attacks, aggressive postures, lateral threats, tail rattling and pursuit frequency. MJ (1, 5, 10 mg/kg) produced a significant dose-dependent decrease in offensive aggressive behaviors. MJ did not impair the defensive mechanisms of the animals and its anti-aggressive effect was not accompanied by sedation or catalepsy. PCPA (50 mg/kg), an inhibitor of 5-hydroxytryptamine (5-HT) biosynthesis, produced a significant increase in aggressive responses and reversed the anti-aggressive effect of MJ. Additionally, FL (10 mg/kg), a 5-HT reuptake inhibitor, produced a significant suppression of aggressive behaviors and also enhanced the antiaggressive effect of MJ. Taken together, these findings suggest that methyl jasmonate exhibits specific anti-offensive aggressive activity and may be relevant in the treatment of reactive aggression in humans. Although, it appears that MJ may be affecting 5-HT(1B) receptors, additional data are needed to clearly define the mechanism(s) by which MJ exhibit antiaggressive activity.

Psychopharmacological properties of an aqueous extract of Tetracarpidium conophorum Hutch. & Dalziel in mice.

The extract of the nut of Tetracarpidium conophorum (TC), commonly known as African walnut, is widely used to relieve pain, increase sperm count, enhance sexual performance in males and as a nerve tonic in ethnomedicine. This study describes the psychopharmacological properties of the aqueous extract of the nut of TC in mice. The spectrum of activities studied were the effects of TC on the duration of immobility in the forced swim test of the behavioural despair model of depression; prolongation of the duration of sleep produced by thiopentone; amphetamine-induced stereotyped behaviour; and on pain episodes produced by acetic acid and by formalin. Orally administered TC (50-200 mg/kg) produced a significant and dose-related decrease in the duration of immobility in the forced swim test in mice. TC also exhibited analgesic property, as shown by its ability to reduce the frequency of abdominal constrictions induced by acetic acid and to inhibit the nociceptive responses produced by formalin. However, at the tested oral doses of 50-200 mg/kg, TC did not prolong the duration of sleep produced by thiopentone nor alter the pattern of the stereotyped behaviour induced by amphetamine. This investigation provides evidence that may support the ethnomedicinal applications of the extract of the nut of TC in the treatment of pain. The study also revealed that TC seems to demonstrate antidepressant-like activity, as evidenced by its ability to shorten the period of immobility in the forced swim test; however, further studies are necessary to clearly define the role of TC in depression.

Antidepressant activity of methyl jasmonate, a plant stress hormone in mice.

Methyl jasmonate (MJ) is a hormone released by plants in response to external stress, injury or pathogenic invasions. This present investigation evaluated the antidepressant effect of intraperitoneal doses of MJ in mice. Mice were given MJ in the doses of 10, 25 and 50 mg/kg daily for 7 days and then subjected to forced swim test (FST), tail suspension test (TST) and yohimbine lethality test (YLT). The results showed that MJ produced a significant decrease in the period of immobility in the FST and TST, indicating antidepressant activity. MJ potentiated the toxic effect of yohimbine in the YLT, which further suggests antidepressant property and also indicates facilitatory effect on both serotonergic and noradrenergic systems respectively. However, MJ did not significantly alter the spontaneous motor activity of the animals, which indicates a lack of central nervous system stimulant effect. Taken together, these findings suggest that MJ has antidepressant activity and the mechanisms underlying this effect may involve serotonergic and noradrenergic systems.