[The effect of a magnesium-free solution on neuronal activity in the snail]

This investigation has revealed that application of magnesium-free medium to snail brain preparations results in the development of paroxysmal depolarization shifts (PDSs) and depolarizing afterpotentials in some neurons. The neurons studied were classified by their responses to low extracellular magnesium as active or passive. In the active neurons, typical PDSs observed were characterized by plateau potential with complete inactivation of the spike generating mechanism. In the passive neurons the magnitude of PDSs was sufficient to inactivate the mechanism of spike generation. The PDSs were synchronized in synaptically unconnected neurons. The results show that the snail brain preparation immersed to the magnesium-free solution is a suitable model of experimental epilepsy, since Helix nerve cells are easy to identify.