Effect of beta-myrcene on pentobarbital sleeping time

Evidence that beta-myrcene (MYR) interferes with the metabolic activation of premutagens has been provided by in vitro studies. In order to determine whether MYR also interferes with the in vivo metabolism of xenobiotics, thereby modifying pharmacological responses to drugs, we investigated the effects of this monoterpene on pentobarbital (PT) sleeping time in rats. Two experiments were carried out. In the first, a single dose of MYR (0.25, 0.5 or 1.0 g/kg po) was given 1 h before PT (40 mg/kg ip). No effect was observed with the two lowest doses, but the highest MYR dose given 1 h before PT increased the PT-induced sleeping time (131 +/- 15 min vs 64 +/- 15 min for controls, mean +/- SD). In the second experiment, male rats were treated with MYR (1.0 g/kg po once a day) for 14 days and injected with PT (40 mg/kg ip) 24 h after the last dose of MYR. Repeated treatment with MYR markedly reduced PT sleeping time compared to the vehicle-treated control group (21 +/- 13 min vs 35 +/- 19 min for controls, mean +/- SD). These results indicate that MYR interferes with the in vivo barbiturate metabolism and support the view that MYR induces the phenobarbital-inducible cytochrome P-450 (P-450 2B subfamily) enzymes in the rat

Neurobehavioral study of the effect of beta-myrcene on rodents

Tea prepared from lemongrass (Cymbopogon citratus) is used for its supposed anxiolytic, hypnotic and analgesic properties in Brazilian folk medicine. beta-Myrcene, a major constituent of lemongrass, produces analgesia in rodents but there is some controversy about whether this actions is central or peripheral or both. Rats and mice received beta-myrcene, 1 g/Kg po in corn oil alone 1 h before being evaluated for a series of responses which included exploratory and emotional behavior, anxiolytic activity in a plus maze and inhibition of conditioned avoidance. No evidence was demonstrable for an effect of beta-myrcene on any f these behaviors. Similarly, beta-myrcene had no protective effect on pentylenetetrazol (PTZ)-induced seizures in mice. These data suggest that beta-myrcene has no benzodiazepine-like anxiolytic activity and that an activity on the central nervous system (antidepressive or antipsychotic) is unlikely. Despite the negative results of this study, folk use of lemongrass tea may still be justified by its analgesic properties

Toxicological study of the molluscicidal latex of Euphorbia splendens: irritant action on skin and eye

Aqueous solutions of the molluscicidal latex of Euphorbia splendens are irritant to the rabbit eye in concentrations higher than 0.35% and to the rabbit skin in concentrations higher than 0.5%. Although this irritant potential does not proclude its use as a molluscicide, special precautions are recommended for hanbdling and application of the product and the hazard of skin tumor-promoting potencial should be carefully investigated before its use for schistosomiasis vector control.

Comparison of five methods for the determination of lethal dose in acute toxicity studies

The aim of the prsent study was to compare the realibility of LD50 determination using the traditional Litchfield and Wilcoxon method with that obtained by forur alternative tests requiring smaller numbers of animals, for the purpose of classifyng chemicals according to their acute toxicity. Acute lethal dose determinations were carried out in mice for oral and intraperitoneal administration of hexachlorophene, lidocaine, methanol, phenobarbital and physostigmine. The Molinengo method proved not to be as reliable as suggested by its author. Determination of LD50 using the Thompson and Weil method or, alternatively, the maximal non-lethal dose and the approximate lethal dose permitted the classification of the chemicals in essentially the same order. The approximate lethal dose method, in particular, seems to be a very suitable alternative method to the classical LD50 test since it requires only about 6 animals, provides enough information to order chemicals according to their toxicities, and provides useful information for planning subsequent repeated-dose studies