Abstracts

RATIONALE: Palmitone is a phytodrug with antiepileptic effects, isolated from the leaves of Annona diversifolia (Annonaceae). Although its mechanisms of action are not known yet, our previous experiments suggested a facilitation of inhibitory systems. The present study was carried out to evaluate the effects of single and repetitive administration of palmitone in the levels of benzodiazepine (BDZ) and delta opioid receptors in the mice brain, using an in vitro autoradiography procedure. METHODS: Taconic (SW) male mice (25-30 g)were used. Control group (n=6) received a vehicle injection (saline solution in Tween 80, i.p., 0.1 ml/10 g). The experimental groups were treated with palmitone (5 mg/kg, i.p.)as follows: a single (n=5) or repetitive administration (n=5)(one daily injection during 7 days). Animals were sacrified by decapitation 24 h after the last injection. Coronal brain frozen sections (20 mm) were obtained and used for autoradiography experiments carried out to label BDZ ( 3H -Flunitrazepam 2 nm) and delta opioid ( 3H -DPDPE, 10 nm) receptor binding. RESULTS: Concerning BDZ receptors, animals treated with palmitone (single and repetitive administration) showed decreased levels of receptor binding in cortex (42% and 41%), caudate putamen (53% and 35%), amygdala (30% and 33%) and hippocampus (40% and 35%). About delta receptors, a significant diminution in the levels of receptor binding was detected following repetitive administration of palmitone in cortex(54%), caudate putamen (49%), amygdala (45%) and hippocampus (48%). CONCLUSIONS: The decreased BDZ receptor binding detected in our experiments supports that palmitone may have a modulatory effect on the GABAergic system. On the other hand, the reduced delta receptor binding after repetitive palmitone administration could be the result of an opioid-GABA interaction. Partially supported by Instituto Mexicano de Psiquiatria 3280 and CONACyT 31702-M and fellowship #115173).