A Novel Photocaged Adenosine A1 Receptor Agonist for Closed-loop Optical Control of Hippocampal Neurotransmission and Suppression of Epileptiform Bursts in an Ex Vivo Slice Model for Epilepsy
Abstract number :
1.027
Submission category :
1. Basic Mechanisms / 1C. Electrophysiology/High frequency oscillations
Year :
2022
Submission ID :
2204158
Source :
www.aesnet.org
Presentation date :
12/3/2022 12:00:00 PM
Published date :
Nov 22, 2022, 05:23 AM
Authors :
Erine Craey, MSc – Ghent University; Jeroen Spanoghe, MSc – Head and Skin – Ghent University; Simona Manzella, MSc – Head and Skin – Ghent University; Lars Larsen, PhD – Head and Skin – Ghent University; Evelien Carrette, PhD – Head and Skin – Ghent University; Jean Delbeke, MD, PhD – Head and Skin – Ghent University; Kristl Vonck, MD, PhD – Head and Skin – Ghent University; Serge Van Calenbergh, PhD – Pharmaceutics – Ghent University; Paul Boon, MD, PhD – Head and Skin – Ghent University; Wytse Wadman, PhD – Head and Skin – Ghent University; Robrecht Raedt, PhD – Head and Skin – Ghent University
Rationale: Adenosine A1 receptors modulate neuronal activity through pre- and postsynaptic routes. Activation of these receptors was proven to have seizure-suppressive effects. Unfortunately, the ubiquity of A1 receptors demands focal activation with temporal precision for specific therapeutic intervention. With photocaging, the ligand of interest is linked to a photocleavable caging group that can only be removed upon illumination with light of an appropriate wavelength, thus allowing for timed site-specific ligand release. In this study, we explore whether closed-loop optical control of the coumarin-caged A1 agonist N6-cyclopentyladenosine (cCPA) can be used to modulate neurotransmission and suppress epileptiform bursts in the high potassium slice model for epilepsy.
Methods: Extracellular CA1 field potentials (fEPSPs) were evoked by Schaffer collateral stimulation and recorded with a multielectrode array in acute rat hippocampal slices. Slices were incubated with 3µM cCPA under dark conditions and repeated electrical pulses (10 s interval; fixed stimulation intensity) were given to monitor the efficiency of CA1 neurotransmission over time (as reflected by the fEPSP amplitude). Following baseline amplitude monitoring, potassium concentration was increased from 3.25 mM to 8.5 mM causing an increase in fEPSP amplitude. A 4 mW LED light flash (405 nm) of 50 ms was delivered to release CPA whenever the fEPSP amplitude surpassed 115% of its mean baseline value (target); thus constituting a closed-loop optical uncaging system.
Results: Within the high potassium slice model, the closed-loop system was able to keep the fEPSP amplitude stable around target value (Figure 1). Consequently, generation of high potassium-induced epileptiform bursts was prevented in three out of four slices. Interruption of the loop resulted in a gradual increase of both fEPSP amplitude and burst frequency. Eventually, the loop was closed again leading to a clear reduction of fEPSP amplitude back to target value accompanied by a decrease in burst frequency in all slices.
Conclusions: Closed-loop optical uncaging allows to control the level of hippocampal neurotransmission under high potassium conditions while suppressing epileptiform bursts, making this approach a potential candidate for focal suppression of seizure activity while preserving functional neurotransmission.
Funding: The Research Foundation - Flanders (FWO)
Basic Mechanisms