Hyperthermia-Induced Seizures Enhance Brain Concentrations of the Endocannabinoid-Related Linoleoyl Glycerols in a Scn1a+/- Mouse Model of Dravet Syndrome.

Abstract

Introduction: The endocannabinoid system contributes to the homeostatic response to seizure activity in epilepsy, a disease of brain hyperexcitability. Indeed, studies using conventional epilepsy models have shown that seizures increase endocannabinoids in the brain. However, it is unknown whether endocannabinoids and structurally related fatty acid amides and monoacylglycerols are similarly released in response to acute seizures in animal models of drug-resistant epilepsy. Therefore, in this study, we investigated whether a hyperthermia-induced seizure increased concentrations of endocannabinoids and related signaling lipids in the Scn1a+/- mouse model of Dravet syndrome. Materials and Methods: We compared hippocampal concentrations of the major endocannabinoids and related monoglycerols and N-acylethanolamines in wild-type mice, naïve Scn1a+/- mice, and Scn1a+/- mice primed with a single, hyperthermia-induced, generalized tonic-clonic seizure. Samples were collected 5 and 60 min following the seizure and then analyzed with LC-MS/MS. Results: We found that a hyperthermia-induced seizure in Scn1a+/- mice did not affect hippocampal concentrations of the major endocannabinoids, 2-AG and anandamide, or the N-acylethanolamines studied, although the sampling of tissue 5 min postseizure may have been too late to capture any effect on these lipids. Heterozygous deletion of Scn1a alone did not affect these lipid signaling molecules. Notably, however, we found that a hyperthermia-induced seizure significantly increased hippocampal concentrations of the monoacylglycerols, 2-linoleoyl glycerol (2-LG) and 1-linoleoyl glycerol (1-LG), in Scn1a+/- mice. Conclusions: Our results show the unprecedented elevation of the lesser-studied endocannabinoid-related monoacylglycerols, 2-LG and 1-LG, following a hyperthermia-induced seizure in a mouse model of Dravet syndrome. Future research is needed to comprehensively explore the function of these lipid signaling molecules during seizure activity and whether their actions can be exploited to develop new therapeutics.