Abstracts

Furothyl-induced seizures have been shown to increase Immediate Early Gene (IEG) expression (c-fos, c-jun) in mice and valproic acid (VPA), but not lamotrigine, has been shown to prevent seizure-dependent c-fos expression. The ketogenic diet (KD) is effective against many types of epilepsy in children and adolescents and against a variety of acute seizures induced in experimental animals. The KD has also been shown to be as effective as high-dose VPA in suppression of pentylenetetrazole-induced seizures. Valproic acid and the KD differ with respect to MES seizures: VPA reduces seizure severity but the KD makes such seizures more severe. We wished to detemine whether the increased severity of MES seizures in KD-fed rats would either elevate, or decrease, IEG expression compared to those fed a control diet. Half of a cohort of male Harlan Sprague-Dawley rats were switched from a rodent chow diet (Purina 5001) fed ad libitum to a ketogenic diet (BioServe F3666) fed at 100% of caloric daily requirement, calculated on the basis of body weight, at the time they began the diet (age P47) and this amount was kept constant until seizure testing at age P67. Tail vein blood was obtained at the time of seizure testing and levels of [beta]-hydroxybutyrate (Stat-Site, Stanbio, Boerne, TX) and glucose (PrecisionXtra, Abbott, Chicago, IL) were measured just prior to seizure testing. Maximal electroshock seizures were induced by means of ear clip electrodes delivering a constant-current pulse (99 mA, 299 Hz, 9 ms. pulse duration; Ugo Basile ECT Unite 7801). Seizure severity was taken as the extension/flexion (E/F) ratio. Twenty-micrometer coronal serial sections were taken at the levels of the locus coeruleus and hippocampus. In situ hybridization with an oligonucleotide probe complementary to c-fos mRNA was performed. c-fos mRNA expression was measured in the cortex, septum, locus coeruleus, ventromedial hypothalamus, dentate gyrus, CA3 and CA1. At the time of seizure testing KD-fed rats showed elevated blood levels of [beta]-hydroxybutyrate, lowered blood glucose levels and increased seizure severity compared to chow-fed controls. There were no differences in c-fos mRNA expression in KD-fed vs. control rats in any brain area examined. Consistent with observations in other laboratories, however, c-fos mRNA was highest in VMH in response to MES in both control and KD-fed rats. The KD is not protective against MES seizures and actually makes them more severe. It has no effect upon c-fos mRNA expression, however. This finding may suggest that the KD, while not protective, does not lead to increased IEG expression despite elevation in seizure severity. The uniquely elevated expression in VMH serves as a positive control, indicating that the IEG assay was fully functional. (Supported by Department of Biology, Georgetown University and VAMC, Seattle WA)