Abstracts

Diacylglycerol kinase (DGK ) regulates seizure susceptibility and long-term potentiation through arachidonoyl-inositol lipid signaling (PNAS, USA 98:4740; 2001). To study the significance of arachidonoyl-diacylglycerol (20:4 DAG) in epileptogenesis, we used mice deficient in DGK (DGK -/-) in the rapid kindling epileptogenesis model. Male mice (C57BL/6; 20-25 g) were used. Tripolar electrode units (Plastic One Inc., Roanoke, VA) were implanted in the right dorsal hippocampus. Ten days post surgery, kindling was achieved by stimulating 6 times daily for 4 days with a subconvulsive electrical stimulation (a 10-s train containing 50-Hz biphasic pulses of 300-[mu]A amplitude) at 30-min intervals. After 1 week another session of stimulation (rekindling) was given. Seizures were graded according to Racine[rsquo]s Scale. Mice are considered kindled when they display three consecutive stage-5 seizures. The EEG was recorded through electrodes using Enhanced Graphics Acquisition for Analysis (Version 3.63 RS Electronics Inc. Santa Barbara, CA.) and the EEG was analyzed using Neuroexplorer Software (Next Technology) in order to characterize the epileptogenic events as spike, sharp waves, or abnormal amplitude and rhythms. DGK -/- mice displayed significantly fewer motor seizure and epileptic events as compared to wild-type mice from the second day of stimulation, and these differences were maintained during the rekindling session. DGK -/- mice also exhibited a low-amplitude spike-wave complex, short spreading depression, and a predominant lower (1 Hz [ndash] 4 Hz)-frequency band throughout stimulation, while wild-type mice exhibited increased high-frequency band (4 Hz-8 Hz; 8 Hz-15 Hz) from the second day of the stimulation, as determined by power spectral analysis. DGK modulates kindling epileptogenesis through inositol lipid signaling. Because arachidonate-containing diacylglycerol phosphorylation to phosphatidic acid is selectively blocked in the -/- mice, we postulate that the shortage of arachidonoyl-moiety inositol lipids and/or the messengers derived thereof are engaged in the changes uncovered by our work. We are currently studying how lipid synaptic circuitry is inter-regulated during epileptogenesis. (Supported by NIH NS23002.)