Abstracts

Rationale: Increased activity of mTOR has been demonstrated in cortical dysplasia and tuberous sclerosis complex, as well as in animal models of epilepsy. Recent studies in such models revealed that inhibiting mTOR with rapamycin effectively suppressed seizure activity. We used the neuron subset-specific (NS-Pten) conditional knockout mice in our studies. The phosphatase and tensin homolog (PTEN) gene encodes a phosphatase that negatively regulates the mammalian target of rapamycin (mTOR) pathway. The NS-Pten mice show a severe epilepsy phenotype where abnormal epileptiform activity that is evident by 4 wks of age, cytomegalic neurons in the subset of neurons with Pten knockout, ataxia, and premature death. We evaluated the efficacy of an intermittent rapamycin treatment protocol beginning at 4 wks of life on epilepsy progression in these mice. In addition, we evaluated whether rapamycin treatment later in life was effective at reversing the epilepsy progression. Methods: NS-Pten knockouts were treated with a single course of rapamycin during postnatal weeks four and five, or intermittently over a period of five months. The late treatment group started rapamycin treatment on the ninth week, which continued for nine weeks. Epileptiform activity was monitored using video-EEG recordings, and neuroanatomical assessments were made with immunohistochemistry. We also assessed downstream mTOR targets using western blotting. Results: NS-Pten knockouts treated with a single course of rapamycin had recurrence of epilepsy four to seven weeks after treatment ended (p < 0.05). In contrast, epileptiform activity remained suppressed, and survival increased if knockout mice received additional rapamycin during weeks 10-11 (p < 0.05) and 16-17. Aberrant mossy fiber sprouting, present by four weeks of age and progressing in parallel with epileptiform activity, was also blocked by rapamycin (p < 0.01). Analysis of the data from pilot studies using late rapamycin treatment is currently underway. Using biochemistry, we confirmed that rapamycin treatment inhibited downstream mTOR activation. Conclusions: NS-Pten knockouts treated with a single course of rapamycin had recurrence of epilepsy four to seven weeks after treatment ended (p < 0.05). In contrast, epileptiform activity remained suppressed, and survival increased if knockout mice received additional rapamycin during weeks 10-11 (p < 0.05) and 16-17. Aberrant mossy fiber sprouting, present by four weeks of age and progressing in parallel with epileptiform activity, was also blocked by rapamycin (p < 0.01). Analysis of the data from pilot studies using late rapamycin treatment is currently underway. Using biochemistry, we confirmed that rapamycin treatment inhibited downstream mTOR activation.