Abstracts

Rationale: The ketogenic diet (KD) has been an effective antiepileptic treatment dating back to the mid-1920s.  While a number of hypotheses have been advanced, the exact cellular mechanism that underlies the antiepileptic action of the KD remains unclear.  Evidence has been accumulating that ketones can directly enhance voltage-gated potassium currents gated by potassium channel complexes that contain Kvβ2 auxiliary sub-units which themselves possess an aldo-keto reductase enzymatic core domain.  Therefore, we advance the novel hypothesis that ketones generated under ketogenic conditions directly interact with Kvβ auxiliary sub-units to increase voltage-gated potassium currents which in turn reduces neuronal excitability. Methods: At 8 weeks of age, wild-type (WT) and Kvβ2-/- (KO) mice were separated into two groups, one of which was fed standard chow, and the other which was fed a KD for a minimum of 6 weeks. Ex vivo coronal and modified horizontal slices were prepared from each group. In virto extracellular field potential recordings were made from either the dorsal hippocampus (HP) of the coronal slices, or the ventral HP, entorhinal cortex (EC) and lateral amygdala (LA) simultaneously in modified horizontal slices in standard aCSF, with or without the addition of ketones. Epileptiform bursts were induced by removing Mg2+ and increasing K+ concentrations in the aCSF ([Mg2+]0 aCSF).  The percentage of slices that exhibited bursting, latency to continuous bursting, and inter-burst interval, were measured for at least one hour after perfusion with the ([Mg2+]0 aCSF). Results: In WT mice, acute application of ketones to slices from animals that were not maintained on a KD significantly reduced the induction of ictal events in the ventral HP. This effect is ventral HP specific and was not seen in the dorsal HP, KO mice or animals maintained on a KD. In the ventral HP, ketogenic conditions caused a significant reduction in the latency to ictal events regardless of genotype, however, in the dorsal HP, this reduction not observed in KO slices. In both the ventral HP and the LA, maintenance of WT animals on the KD causes a reduction in the inter-burst interval, which is not seen in slices made from KO animals. This effect is not seen in the EC or the dorsal HP. Additionally, treatment with the KD appears to alter the functional connectivity in the brain, regardless of genotype, as measured by the order in which the three areas (HP, EC, & LA) begin bursting after induction with ([Mg2+]0 aCSF). Conclusions: Although it is not clear exactly how KvB2 is modulating the effects of the ketogenic diet, it is clear that these effects differ across brain regions, indicating that the ketogenic diet affects separate regions of the brain in different ways. Funding: DoD PR1215668