The leaf essential oil of Psidium guyanensis offers protection against pentylenetetrazole-induced seizures.

The essential oil obtained from the leaves of Psidium guyanensis Pers. (Myrtaceae) was studied against lethal seizures induced by intraperitoneal injection of pentylenetetrazole (80 mg/kg), picroptoxin (6 mg/kg), and strychnine (2 mg/kg) in mice. At oral doses of 100, 200, and 400 mg/kg, the essential oil attenuated the severity of pentylenetetrazole-induced seizures and offered a dose-related protection but it was found to be ineffective against convulsions induced by picrotoxin and strychnine. The blockade of its protective effect on pentylenetetrazole lethal seizures by caffeine (10 and 50 mg/kg, i.p.) suggests a probable participation of endogenous adenosine in its mechanism. Furthermore, a peripheral mechanism also appears to be involved as the essential oil (5-20 micrograms/ml) was able to block selectively the acetylcholine (1.65 x 10(-6) M) induced contractions but not those evoked by high potassium (80 mM) or caffeine (2 x 10(-3) M) on isolated toad rectus abdominis muscle.