Hippocampal Area CA2 as a Novel Therapeutic Target in Epilepsy
Abstract number :
1.007
Submission category :
1. Basic Mechanisms / 1A. Epileptogenesis of acquired epilepsies
Year :
2021
Submission ID :
1826389
Source :
www.aesnet.org
Presentation date :
12/4/2021 12:00:00 PM
Published date :
Nov 22, 2021, 06:53 AM
Authors :
Christos Lisgaras, PhD, MSc, BSc - Departments of Psychiatry, Neuroscience & Physiology, New York University Langone Health, New York, NY 10016, Center for Dementia Research, The Nathan Kline Institute, Orangeburg NY 10962; Azahara Oliva - Department of Neuroscience, Columbia University, New York, NY 10037; Sam Mckenzie - Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM 87131; John LaFrancois - Center for Dementia Research, The Nathan Kline Institute, Orangeburg NY 10962; Steven Siegelbaum - Department of Neuroscience, Columbia University, New York, NY 10037; Helen Scharfman - Departments of Psychiatry, Neuroscience & Physiology, New York University Langone Health, New York, NY 10016, Center for Dementia Research, The Nathan Kline Institute, Orangeburg NY 10962
Rationale: The resistance of hippocampal area CA2 to cell death and its hyperexcitability in temporal lobe epilepsy (TLE) is well known, but a possible CA2-based therapeutic strategy hasn’t been tested in a preclinical setting. Here we address the hypothesis that selective inhibition of CA2 pyramidal neurons in a closed-loop fashion during seizures can inhibit abnormal activity in different mouse models of TLE.
Methods: To target CA2 pyramidal neurons selectively, we used Amigo2-Cre transgenic mice, in which Cre-recombinase is expressed in CA2. We bilaterally injected Cre-dependent viral vectors expressing the inhibitory opsin archaerhodopsin (AAV2/5-EF1a-DIO-eArch3.0-eYFP) or eYFP (AAV2/5-EF1a-DIO-eYFP) into dorsal CA2 of our intrahippocampal kainic acid (IHKA) and pilocarpine (PILO) mouse models, both of which produce frequent spontaneous convulsive seizures. After the onset of spontaneous convulsive seizures, we implanted a depth electrode coupled to an optic fiber in dorsal CA2 and a subdural screw electrode over the right frontal cortex. We then configured a closed-loop protocol to detect spontaneous seizures, interictal spikes (IIS), and high-frequency oscillations (HFOs, >250Hz) in real-time and triggered optogenetic inhibition of CA2 pyramidal cells with a series of 500ms pulses at the time of seizures or IIS, and 10-20ms square or trapezoidal pulses for HFOs. In control experiments, we used no light stimulation, stimulation after a random delay, or light stimulation in eYFP-expressing mice. Finally, in a subset of experiments, we evaluated the effect of light delivery far from the CA2 stimulation site (cortex).
Results: Real-time detection of IIS with time-locked optogenetic inhibition at the IHKA injection site (n=34) significantly reduced IIS amplitude compared to no stimulation (n=175), random stimulation (n=30), or stimulation in eYFP-expressing mice (n=23). A similar suppressive effect of IIS amplitude was found in the PILO model, suggesting generalizability. In both TLE models, spontaneous convulsive seizures were significantly shorter in duration using optogenetic stimulation (30.63±2.9s) compared to no stimulation (51.26±2.0s; p< 0.001, n=3 mice). In the IHKA model, seizure duration was reduced when light was delivered at the site of IHKA injection with no effect on the contralateral cortex, suggesting a focal rather than a global seizure-suppressive effect. Notably, we were able to silence HFOs occurring in slow wave sleep in both TLE models (n=4 mice), which to date presents the first closed-loop manipulation of HFOs.
Basic Mechanisms