關於PDS (paroxysmal depolarizing shift)為什麼會引起seizure 的機制做個補充說明 摘自google~~ The paroxysmal depolarizing shift (PDS) remains the best cellular marker of an epileptic event, corresponding to the interictal spike of the EEG. The PDS represents a sustained movement of the neuronal resting potential above threshold for 10--15 times the duration of a normal action potential. Positive charge is initially carried in through Na+ channels, but Ca++ channels open within a few ms. The Ca++ that enters the cell during the PDS is rapidly bound to calcium binding proteins and sequestered in mitochondria. This prevents the intracellular free Ca++ concentration from becoming excessive and triggering a cascade of cytotoxic events. Below this toxic threshold, Ca++ entry produces a proportional degree of K+ channel opening, which serves to terminate the PDS and induces a prolonged after-hyperpolarization. Failure of this Ca++-dependent K+ current appears to be crucial to the transition from interictal spike to seizure. Why this failure occurs is the subject of current work. --

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