South African traditional medicine inhibits the spontaneous epileptiform discharges in slices of the mouse cerebral cortex

Searsia dentata and Searsia pyroides (Anacardiaceae) are used in traditional South African medicine to treat convulsions and epilepsy. Previous studies have demonstrated that extracts of these plants comprise compounds that bind to the flumazenil-sensitive site on the GABA_A receptor [1]. However, their use as anticonvulsant medicinal plants cannot be adequately explained by these findings. The aim of this study was to examine the possible involvement of the glutamatergic system of extracts from the plants. The mouse cortical wedge preparation was used for functional characterization of the extracts. The affinity towards the NMDA and the AMPA receptor was investigated using classical [³H]GCP39653 and [³H]AMPA binding assays, respectively. The extracts of S. dentata and S. pyroides inhibited the spontaneous epileptiform discharges in mouse cerebral cortical slices with ED₅₀ of 0.62 and 1.67mg dry extract/ml, respectively. Both extracts displaced [³H]CGP39653 binding and significantly inhibited the NMDA-induced response during co-administration in cortical slices. In this study, we have demonstrated the effect on spontaneous epileptiform discharges of these two South African medicinal plants and shown the presence of NMDA receptor antagonists in the crude ethanolic extracts.

References: 1 Svenningsen et al., (2006) Journal of Ethnopharmacology 103:276–280.