Lars Emil Larsen1, Wytse Jan Wadman2, Pieter van Mierlo3, Jean Delbeke4, Annelies Grimonprez4, Bregt Van Nieuwenhuyse4, Jeanelle Portelli5, Paul Boon4, Kristl Vonck4, Robrecht Raedt4. 1. Laboratory for Clinical and Experimental Neurophysiology, Neurobiology and Neuropsychology (LCEN3), De Pintelaan 185, Blok B, Ghent University, BE-9000 Ghent, Belgium. Electronic address: larsemil.larsen@ugent.be. 2. Swammerdam Institute of Life Sciences, University of Amsterdam, The Netherlands. 3. Laboratory for Clinical and Experimental Neurophysiology, Neurobiology and Neuropsychology (LCEN3), De Pintelaan 185, Blok B, Ghent University, BE-9000 Ghent, Belgium; Department of Electronics and Information Systems, Medical Imaging and Signal Processing, Ghent University - iMinds Medical IT Department, Belgium. 4. Laboratory for Clinical and Experimental Neurophysiology, Neurobiology and Neuropsychology (LCEN3), De Pintelaan 185, Blok B, Ghent University, BE-9000 Ghent, Belgium. 5. Laboratory for Clinical and Experimental Neurophysiology, Neurobiology and Neuropsychology (LCEN3), De Pintelaan 185, Blok B, Ghent University, BE-9000 Ghent, Belgium; Department of Pharmaceutical Chemistry, Drug Analysis & Drug Information, Center for Neurosciences, Vrije Universiteit Brussel, Belgium.
Abstract
BACKGROUND: Vagus Nerve Stimulation (VNS) has seizure-suppressing effects but the underlying mechanism is not fully understood. To further elucidate the mechanisms underlying VNS-induced seizure suppression at a neurophysiological level, the present study examined effects of VNS on hippocampal excitability using dentate gyrus evoked potentials (EPs) and hippocampal electroencephalography (EEG). METHODS: Male Sprague-Dawley rats were implanted with a VNS electrode around the left vagus nerve. A bipolar stimulation electrode was implanted in the left perforant path and a bipolar recording electrode was implanted in the left dentate gyrus for EEG and dentate field EP recording. Following recovery, VNS was applied in freely moving animals, using a duty cycle of 7 s on/18 s off, 30 Hz frequency, 250 µs pulse width, and an intensity of either 0 (SHAM), 25 µA or 1000 µA, while continuously monitoring EEG and dentate field EPs. RESULTS: VNS at 1000 µA modulated dentate field EPs by decreasing the field excitatory post-synaptic potential (fEPSP) slope and increasing the latency and amplitude of the population spike. It additionally influenced hippocampal EEG by slowing theta rhythm from 7 Hz to 5 Hz and reducing theta peak and gamma band power. No effects were observed in the SHAM or 25 µA VNS conditions. CONCLUSION: VNS modulated hippocampal excitability of freely moving rats in a complex way. It decreased synaptic efficacy, reflected by decreased fEPSP slope and EEG power, but it simultaneously facilitated dentate granule cell discharge indicating depolarization of dentate granule cells.
BACKGROUND: Vagus Nerve Stimulation (VNS) has seizure-suppressing effects but the underlying mechanism is not fully understood. To further elucidate the mechanisms underlying VNS-induced seizure suppression at a neurophysiological level, the present study examined effects of VNS on hippocampal excitability using dentate gyrus evoked potentials (EPs) and hippocampal electroencephalography (EEG). METHODS: Male Sprague-Dawley rats were implanted with a VNS electrode around the left vagus nerve. A bipolar stimulation electrode was implanted in the left perforant path and a bipolar recording electrode was implanted in the left dentate gyrus for EEG and dentate field EP recording. Following recovery, VNS was applied in freely moving animals, using a duty cycle of 7 s on/18 s off, 30 Hz frequency, 250 µs pulse width, and an intensity of either 0 (SHAM), 25 µA or 1000 µA, while continuously monitoring EEG and dentate field EPs. RESULTS: VNS at 1000 µA modulated dentate field EPs by decreasing the field excitatory post-synaptic potential (fEPSP) slope and increasing the latency and amplitude of the population spike. It additionally influenced hippocampal EEG by slowing theta rhythm from 7 Hz to 5 Hz and reducing theta peak and gamma band power. No effects were observed in the SHAM or 25 µA VNS conditions. CONCLUSION: VNS modulated hippocampal excitability of freely moving rats in a complex way. It decreased synaptic efficacy, reflected by decreased fEPSP slope and EEG power, but it simultaneously facilitated dentate granule cell discharge indicating depolarization of dentate granule cells.
Authors: Jordan Lam; Ryan P Cabeen; Runi Tanna; Lauren Navarro; Christianne N Heck; Charles Y Liu; Brian Lee; Jonathan R Russin; Arthur W Toga; Darrin J Lee Journal: World Neurosurg Date: 2021-02-04 Impact factor: 2.104
Authors: Meghan A L Quinlan; Vanessa M Strong; Darlene M Skinner; Gerard M Martin; Carolyn W Harley; Susan G Walling Journal: Front Syst Neurosci Date: 2019-01-09