Relevant to neuronal activity, AMPKmediated changes in long-term potentiation are mTOR-dependent. Differences in acute seizure test profiles between three different treatments that affect AMPK activity support the hypothesis that downstream effects of neuronal mTOR inhibition likely depend on additional factors specific to each intervention. Rapamycin is known to bind FKBP12 to specifically inhibit mTORC1activity. Evidence that rapamycin acts similarly in vivo is shown by the ability of rapamycin and its derivatives to decrease recurrent seizures in animals and patients where TORC1 activity is abnormally high. Thus, it generally is LY294002 154447-36-6 assumed that rapamycin exerts its antiseizure actions by decreasing TORC1 activity. Protection in drug-induced chronic seizure models raises the possibility that mTOR inhibitors reverse a seizureinduced increase in the mTOR pathway. Specifically, after kainic acid-induced status epilepticus, increases in mTOR activity are noted 1-6 h after seizure onset, then decrease to baseline values, only to increase again 3 days after onset. Both of these increases are reversed by administration of rapamycin. However, the connection between mTOR activity and excessive neuronal activity during seizures is not clear. mTOR activity is required in dendrites for arbor and spine morphogenesis in some studies, raising the possibility that these changes in neuronal morphology may impact seizures and/or epilepsy. Rapamycin also inhibits mossy fiber sprouting in a Fingolimod number of models of status epilepticus. However, the importance of inhibiting mossy fiber sprouting is unclear because rapamycin can prevent mossy fiber sprouting without protecting against seizures after pilocarpine-induced status epilepticus. Electrophysiologically, mTOR is necessary for long-term potentiation and long-term depression.The effect of rapamycin on synaptic transmission may be mediated via decreased neuronal excitability and/or neurotransmitter release. Whether these morphological and physiological effects are the specific mechanism of seizure protection is unclear. In summary, decreased rapamycin-related neuronal excitability in some paradigms may be the result of mTOR inhibition but these studies do not rule out the possibility of an “off-target” effect, particularly given the broad effects of mTOR activity on protein synthesis, lipid metabolism, and autophagy. The limited seizure protection after a 3 d rapamycin exposure in the seizure-na? ��ve mice studied here may be due to unintended deleterious effects of prolonged mTOR suppression, in contrast to physiological mTOR suppressors where mTOR activity eventually rebounds. Another potential explanation is that the 3 d rapamycin regimen used here may suppress activity of the other mTOR protein complex, TORC2, with a subsequent deleterious effect on Akt activity. Consistent with only transient protection in the MES-T test, there may be an optimal degree of timing or extent of mTOR suppression that confers seizure 
protection in preclinical tests, though it is conceivably difficult to pharmacologically achieve such a balance. Finally, rapamycin is unlikely to have global antiseizure benefits, as it fails to protect in a model of infantile spasms induced by betamethasone and NMDA, even when administered before and after spasms started. Pretreatment or sustained exposure to rapamycin appears to be necessary to prevent seizures in preclinical models, as outlined previously. A requirement for prolonged rapamycin treatment is consistent with our finding that a 3-day treatment with rapamycin is more effective than a short 6 h treatment prior to kainic acid-induced seizures.