Inhibitory effect of phenytoin on intracellular cyclic nucleotide and calcium changes during pentylenetetrazole-induced bursting activity in snail neurons.

Effects of phenytoin (PHT) on the intracellular calcium reservoir, lysosome-like granules (LLG), and calcium-related intracellular events during pentylenetetrazole (PTZ)-induced bursting activity in the neurons of the Japanese land snail, Euhadra peliomphala, were examined. PTZ-induced morphological change of LLG was inhibited by PHT. Calcium release from LLG was inhibited by PHT. PHT also inhibited the cyclic AMP increase by PTZ. PHT inhibited the increase in calcium-dependent protein kinase activity during PTZ-induced bursting activity. These findings suggest that PHT inhibits, as a first step, cyclic AMP increase which is one of the trigger factors of bursting activity as well as subsequent calcium-related intracellular pathological changes during seizure activity.