Closed-loop rescue of sudden unexpected death in epilepsy by regulating dorsal raphe functions - PROJECT SUMMARY Sudden unexpected death in epilepsy (SUDEP) is the primary cause of death in individuals with epilepsy, representing a significant public health concern. Unfortunately, there are currently no methods to predict or prevent SUDEP. In recent work, we demonstrated that ictal (i.e., during a seizure) local field potential (LFP) suppression in the dorsal raphe nucleus (DRN) precedes seizure-induced sudden death in a mouse model of SUDEP. In unpublished data, we can significantly reduce the SUDEP rate using closed-loop electrical DRN stimulation upon detecting ictal DRN LFP suppression. Our preliminary data also point to reduced ictal serotonergic (5-HT) neuronal activity and increased extracellular GABA levels in the DRN of SUDEP model mice. Building on our compelling preliminary results, we propose to test whether closed- loop stimulation of ictal DRN function can prevent SUDEP in two mouse models (Aim 1) and further refine this therapeutic approach by elucidating the cellular (Aim 2) and synaptic (Aim 3) mechanisms of ictal DRN function in regulating SUDEP. This proposal will test our data-driven central hypothesis that closed-loop restoration of DRN neuronal activities prevents SUDEP by modulating 5-HT and GABAergic systems. This hypothesis will be tested via the following specific aims in two SUDEP mouse models. In Aim 1, we will leverage logistic regression and two newly developed machine-learning techniques to identify ictal events that can predict the lethality of seizures. We will then test whether closed-loop ictal DRN electrical stimulation can prevent SUDEP. In Aim 2, we will determine the dynamics of DRN5-HT and DRNGABA neuronal activities (calcium imaging) during fatal seizures using simultaneous LFP-fiber photometry recordings. We will subsequently assess their contribution to SUDEP by utilizing the closed-loop optogenetic approach to selectively manipulate DRN5-HT and DRNGABA neuronal activity when fatal seizures are detected. In Aim 3, we will delineate the specific contributions of GABAergic synaptic inputs to DRN by inhibiting GABA release at DRN presynaptic terminals. Using parapinopsin (PPO) for presynaptic optogenetic inhibition, we will target GABAergic inputs from each of the DRNGABA, the bed nucleus of the stria terminalis (BNSTGABA), and central amygdala (CeAGABA), and subsequently assess their efficacy in rescuing SUDEP. We have developed and validated the necessary tools for accomplishing these cohesive aims to expand our knowledge of SUDEP and develop effective SUDEP prevention strategies toward clinical translation.
