Clinical and experimental studies have shown that SE evolves through an initiation phase to a maintenance phase. In the initiation phase the triggering stimuli evoke discrete seizures that tend to abate as soon as the stimulus is removed. In the subsequent maintenance phase discrete seizures coalesce together into a continuum, with triggering stimuli no longer required to sustain a train of seizures. The intensity and duration of the stimulation has a direct influence on the transition from the initiation phase to the maintenance phase. A variety of signaling molecules such as GABA-A (γ-aminobutyric acid) antagonists, glutamate agonists, cholinergic (muscarinic) agonists, tachykinins, galanin antagonists, and opiate k antagonists have been found to be involved in the initiation phase. In contrast to this, much less is known about the maintenance phase. In fact only a limited number of molecules have been found that block the maintenance phase (e.g., NMDA (N-methyl-D aspartate) antagonists, substance P antagonist, galanin, and dynorphin).