BICUCULLINE-INDUCED EPILEPTIFORM ACTIVITY IN RAT HIPPOCAMPAL SLICES -SUPPRESSION BY ACONITUM ALKALOIDS

Alkaloids of Aconitum spec. (Ranunculaceae) are employed in traditiona l Chinese folk medicine as analgesics. The present study was designed in order to investigate the effects of the structurally related alkalo ids aconitine, lappaconitine, and 6-benzoylheteratisine on experimenta lly induced epileptiform activity. Experiments were performed as extra cellular recordings of stimulus evoked population spikes in rat hippoc ampal slices. Epileptiform activity was induced by bicuculline. All th ree alkaloids exerted an inhibitory action on excitability of hippocam pal pyramidal cells in a frequency-dependent manner. The onset of inhi bition was accelerated by increasing the frequency of electrical stimu lation. Aconitine (1 mu M) evoked a complete suppression of both norma l and epileptiform activity, whereas lappaconitine (10 mu M) and 6-ben zoylheteratisine (10 mu M) selectively diminished the epileptiform aft erdischarges and the duration of the bursts, but spared the normal act ivity. The present findings suggest that the structurally related Acon itum alkaloids aconitine, lappaconitine, and 6-benzoylheteratisine pos sess an anticonvulsive potential. The predominant effect of these alka loids is to suppress the spread of seizure activity, and they may ther efore tend to distort epileptic events. However, despite their similar structure, they exert qualitatively and quantitatively different inhi bitory effects.