Abstracts

Rationale: Our group has shown that spontaneous seizures activate extended amygdala (ExtA) neurons in a Dravet Syndrome (DS) mouse model (scn1a+/-), and targeting this region can improve seizure-induced respiratory dysfunction and death in the audiogenic seizure (AGS) mouse DBA1. Odors have been used as therapy for millennia, including epilepsy. However, the mechanisms by which olfactory pathways alter epilepsy remain underexplored. The compound 2-phenylethanol (2PE) has an innately attractive odor in mice, with this attraction behavior dependent on the amygdala. Additionally, 2PE odor can block stress-induced activation of ExtA neurons.

Our goal was to determine if 2PE exposure can alter seizure frequency, severity, or mortality in mouse SUDEP models (scn1a+/- mice and DBA1 AGS mice). We hypothesize that 2PE odorant, acting on olfactory to ExtA pathways, will decrease SUDEP by attenuating neuronal activation in the extended amygdala. We further explore the ability of this odorant to alter respiratory parameters and activity of bed nucleus of the stria terminalis (BNST) neurons.


Methods: DS mice (scn1a+/-) were exposed for at least 8 hrs a day to either 2PE, lemon extract, or vehicle odorant for 15 days starting at postnatal day 20/21. Both before and after odor exposure, respiratory parameters were measured with whole body plethysmography (WBP). Mortality and seizure frequency were recorded. A subset of 2PE exposed animals had an extended washout period to determine the long-term effect of odorant exposure on mortality.

To measure circuit level effects of extended amygdala on odorant exposure, DBA1/J mice were used. The animals are first primed to have repeated seizures as previously described by our group, then a neuronally targeted AAV expressing GCamp6s is injected stereotaxically into the BNST, then the mice are similarly exposed to 15 days of 2PE. The mice are then assessed for seizures with type and latency to seizure measured, and 24 hrs following this ex vivo slices containing the BNST are assessed using single-photon GCaMP imaging.


Results: Our results show a strong trend for decreased mortality in the 2PE exposed scn1a+/- animals (26% mortality 2PE (n=42) vs 48% mortality in vehicle control (n=29, p=0.06 Barnard’s test). The lemon scent exposed animals had no change in mortality (60% mortality, n=13). Preliminary results suggest this effect on mortality is present in DBA1 mice as well, 0/5 2PE exposed mice had a seizure with respiratory arrest vs 2/3 of the vehicle group. BNST neuronal activity in response to 1Hz stimulation was analyzed by averaging the relative activity (dF/F) of each neuron (n=26 2PE, n=29 water) across 4 mice, showing an increase in those animals exposed to 2PE (p=0.031).

Conclusions: Our preliminary data support that 2PE odorant exposure can decrease mortality in mouse models of SUDEP, suggesting that more work to determine the mechanism of action and circuitry involved may illuminate new targets and therapies for preventing SUDEP.

Funding: This work was supported by the National Center for Advancing Translational Sciences (grant number KL2TRO02245), the Dravet Syndrome Foundation, the NIH NINDS R01NS133169 and the Vanderbilt Undergraduate Summer Research Program.