Fatal Epileptic Seizures in Mice Having Compromised Glutathione and Ascorbic Acid Biosynthesis.

Reduced glutathione (GSH) and ascorbic acid (AA) are the two most abundant low-molecular-weight antioxidants in mammalian tissues. GclmKO knockout mice lack the gene encoding the modifier subunit of the rate-limiting enzyme in GSH biosynthesis; GclmKO mice exhibit 10-40% of normal tissue GSH levels and show no overt phenotype. GuloKO knockout mice, lacking a functional Gulo gene encoding L-gulono-γ-lactone oxidase, cannot synthesize AA and depend on dietary ascorbic acid for survival. To elucidate functional crosstalk between GSH and AA in vivo, we generated the GclmKO/GuloKO double-knockout (DKO) mouse. DKO mice exhibited spontaneous epileptic seizures, proceeding to death between postnatal day (PND)14 and PND23. Histologically, DKO mice displayed neuronal loss and glial proliferation in the neocortex and hippocampus. Epileptic seizures and brain pathology in young DKO mice could be prevented with AA supplementation in drinking water (1 g/L). Remarkably, in AA-rescued adult DKO mice, the removal of AA supplementation for 2-3 weeks resulted in similar, but more severe, neocortex and hippocampal pathology and seizures, with death occurring between 12 and 21 days later. These results provide direct evidence for an indispensable, yet underappreciated, role for the interplay between GSH and AA in normal brain function and neuronal health. We speculate that the functional crosstalk between GSH and AA plays an important role in regulating glutamatergic neurotransmission and in protecting against excitotoxicity-induced brain damage.

Modeling pathogenesis and treatment response in childhood absence epilepsy.

OBJECTIVE: Childhood absence epilepsy (CAE) is a genetic generalized epilepsy syndrome with polygenic inheritance, with genes for γ-aminobutyric acid (GABA) receptors and T-type calcium channels implicated in the disorder. Previous studies of T-type calcium channel electrophysiology have shown genetic changes and medications have multiple effects. The aim of this study was to use an established thalamocortical computer model to determine how T-type calcium channels work in concert with cortical excitability to contribute to pathogenesis and treatment response in CAE. METHODS: The model is comprised of cortical pyramidal, cortical inhibitory, thalamocortical relay, and thalamic reticular single-compartment neurons, implemented with Hodgkin-Huxley model ion channels and connected by AMPA, GABAA , and GABAB synapses. Network behavior was simulated for different combinations of T-type calcium channel conductance, inactivation time, steady state activation/inactivation shift, and cortical GABAA conductance. RESULTS: Decreasing cortical GABAA conductance and increasing T-type calcium channel conductance converted spindle to spike and wave oscillations; smaller changes were required if both were changed in concert. In contrast, left shift of steady state voltage activation/inactivation did not lead to spike and wave oscillations, whereas right shift reduced network propensity for oscillations of any type. SIGNIFICANCE: These results provide a window into mechanisms underlying polygenic inheritance in CAE, as well as a mechanism for treatment effects and failures mediated by these channels. Although the model is a simplification of the human thalamocortical network, it serves as a useful starting point for predicting the implications of ion channel electrophysiology in polygenic epilepsy such as CAE.

Melatonin improves sleep in children with epilepsy: a randomized, double-blind, crossover study.

OBJECTIVE: Insomnia, especially maintenance insomnia, is widely prevalent in epilepsy. Although melatonin is commonly used, limited data address its efficacy. We performed a randomized, double-blind, placebo-controlled, crossover study to identify the effects of melatonin on sleep and seizure control in children with epilepsy. METHODS: Eleven prepubertal, developmentally normal children aged 6-11 years with epilepsy were randomized by a software algorithm to receive placebo or a 9-mg sustained release (SR) melatonin formulation for four weeks, followed by a one-week washout and a four-week crossover condition. The pharmacy performed blinding; patients, parents, and study staff other than a statistician were blinded. The primary outcomes were sleep onset latency and wakefulness after sleep onset (WASO) measured on polysomnography. The secondary outcomes included seizure frequency, epileptiform spike density per hour of sleep on electroencephalogram (EEG), and reaction time (RT) measures on psychomotor vigilance task (PVT). Statistical tests appropriate for crossover designs were used for the analysis. RESULTS: Data were analyzed from 10 subjects who completed the study. Melatonin decreased sleep latency (mean difference, MD, of 11.4 min and p = 0.02) and WASO (MD of 22 min and p = 0.04) as compared to placebo. No worsening of spike density or seizure frequency was seen. Additionally, slow-wave sleep duration and rapid eye movement (REM) latency were increased with melatonin and REM sleep duration was decreased. These changes were statistically significant. Worsening of headache was noted in one subject with migraine on melatonin. CONCLUSION: SR melatonin resulted in statistically significant decreases in sleep latency and WASO. No clear effects on seizures were observed, but the study was too small to allow any conclusions to be drawn in this regard.