Abstracts

Rationale: Homeostatic potentiation of synaptic currents in neurons by sleep-like slow wave oscillation(SWO) can activity-dependently amplify both excitatory (EPSC) and inhibitory (IPSC) synaptic currents, resulting in balanced EPSCs and IPSCs in neurons. However, in our idiopathic generalized epilepsy (IGE) mouse models (AES 2017 poster Session #: 2.012), this balance between EPSCs and IPSCs in neurons can be dynamically disrupted by sleep-like SWO activity, which would likely contribute to epileptic activity onset during sleep/quiet-wake period. Since aldehyde dehydrogenase(ALDH) plays a major role in homeostatic plasticity of synaptic currents, we hypothesized that inhibition of ALDH would suppress homeostatic potentiation of spontaneous(s) AMPAR-ESPC, and bring the imbalanced spontaneous(s) EPSCs and sIPSCs back to the balance state due to sleep-like slow wave oscillation. Methods: Ex vivo brain slices were prepared from transgenic IGE mice expressing GABA receptor A322D mutations. Somatosensory cortex layer V neurons were voltage-clamped for sEPSCs (at Cl^- reversal potentials -55.8mV, K-gluconate based internal solution) and sIPSCs recordings(at -60 mV, K-based internal solution, 20 µM NBQX in ACSF). Sleep-like Slow-wave oscillations(SWOs, 0.5Hz and 10 min duration) in neurons (membrane potentials around -75 mV) were induced by injecting cosine depolarizing currents (amplitudes adjusted to generate 4-5 spikes at the oscillation peaks, current-clamp mode). Some slices were treated with 4-diethylaminobenzaldehyde (DEAB in ACSF, 30~40µM) in ACSF (before and during recordings, >1~2 Hours) to suppress ALDH which is a major enzyme necessary for homeostatic plasticity of synaptic currents. Data were collected by using one MultiClamp 700B amplifier (2K Hz filtered) and one Digidata 1400A digitizer (20 KHz sample frequency) and analyzed with Clampfit software. Results: Similar to our previous report(AES 2017 poster Session #: 2.012), SWOs(0.5Hz) could potentiate sEPSCs in neurons from het GABARa^A322D mutant KI mice(from -18.46 ± 1.60 to -29.03 ± 3.42 pA, n=5, paired t-test p=0.02, percentage increase 57 ± 8.13%), not sIPSCs (from -18.65 ± 2.06 to -19.76 ± 2.41 pA, n=5, paired t-test p=0.73), suggesting that the balance between potentiated sEPSCs and sIPSCs in pyramidal neurons is dynamically disrupted. However, after DEAB treatment to suppress ALDH, SWOs could not potentiate both sEPSCs (from -16.95 ± 2.32 to -17.38 ± 2.79 pA, n=11, paired t-test p= 0.623, percentage increase 0.43 ± 4.11%) and sIPSCs (from -17.43 ± 2.45 to -18.65 ± 2.76 pA, n=3), suggesting that with slices being treated with DEAB, the balance between sEPSCs and sIPSCs in pyramidal neurons can be maintained in het mice even following SWOs. Moreover, sEPSC frequency following SWO induction did not significantly change (from 4.35 ± 0.87 Hz to 4.12 ± 0.90 Hz, n=11, paired t-test p= 0.75). Conclusions: In our het IGE mouse model with GABARa A322D mutation, SWOs during sleep and quiet-wake period can create the imbalance between potentiated sEPSCs and un-potentiated sIPSCs in cortical neurons. This imbalance could be brought back to the balance state through DEAB inhibition of ALDH (suppressing homeostatic potentiation of sEPSCs). This would likely offer one potential therapeutic treatment of IGE due to SWOs during sleep or quiet-wake period. Funding: NINDS  R21NS096483