The 4-Aminopyridine Model of Acute Seizures in vitro Elucidates Efficacy of New Antiepileptic Drugs

Abstract

Up to date, preclinical screening for new antiepileptic substances is performed by a combination of different in vivo models of acute seizures, for which large numbers of animals are necessary. So far, little attention has been paid to in vitro models, which are also able to detect antiepileptic efficacy and in principle could likewise serve for exploratory preclinical screening. One of the established in vitro models of acute seizures is the 4-aminopyridine (4-AP) model. Previous studies have shown that the 4-AP model is capable to recapitulate the antiepileptic efficacy of standard antiepileptic drugs (AEDs) such as valproate or carbamazepine. Here, we employed a dual methodological approach using electrophysiology and optical imaging to systematically test the antiepileptic efficacy of three new-generation AEDs with distinct mechanisms of action (lacosamide, zonisamide, and levetiracetam). We found that frequency of 4-AP induced seizure like events (SLE) was the most sensitive parameter to detect dose-dependent antiepileptic effects in these compounds. Specifically, levetiracetam reduced SLE frequency while lacosamide and zonisamide at higher doses completely blocked SLE incidence. Analysis of the intrinsic optical signal additionally revealed a subiculum-specific reduction of the area involved in the propagation of ictal activity when lacosamide or zonisamide were administered. Taken together, our data adds some evidence that acute seizure models in vitro are in principle capable to detect antiepileptic effects across different mechanisms of action with efficacy similar to acute models in vivo . Further studies with negative controls, e.g., penicillin as a proconvulsant, and other clinically relevant AEDs are needed to determine if this acute in vitro model might be useful as exploratory screening tool. In view of the increasing sensitivity toward animal welfare, an affective in vitro model may help to reduce the number of laboratory animals deployed in burdening in vivo experiments and to preselect substances for subsequent testing in time- and cost-laborious models of chronic epilepsy.

Spatiotemporal Correlation of Epileptiform Activity and Gene Expression in vitro

“…SLE extent assessed by comparing the affected area with the total size of a given region revealed the largest expansion of epileptiform activity in the TC (68.8%) followed by the EC (68.1%). In line with the low rate of onset and propagation, expansion of SLEs within the hippocampus was low (34.0%) and involved in most of the cases the subiculum as previously reported ( Heuzeroth et al, 2019 ). All SLEs were associated with an increase in light transmittance with the maximum in the TC (ΔT/T = 2.94%) followed by the EC (ΔT/T = 2.23%) and the H (ΔT/T = 1.98%).…”

“…Institutional security procedures were followed. Experiments were performed using combined hippocampal-entorhinal cortex (EC) slices from rats as previously reported ( Heuzeroth et al, 2019 ) with some modifications. The study design is represented in Figure 1 .…”

Silencing of circIgf1r plays a protective role in neuronal injury via regulating astrocyte polarization during epilepsy

“…4-AP, a nonselective blocker of voltage-gated potassium channels, induces intense electrical discharges in brain slices 32,33 and seizure activity in experimental animals. 34 However, recently studies found that 4-AP could also be used to induce astrocytes activation directly.…”

Dimethylethanolamine Decreases Epileptiform Activity in Acute Human Hippocampal Slices in vitro

“…Induction of epileptiform activity in rodent brain slices can be achieved by a stand-alone manipulation such as inhibition of potassium channels by 4-aminopyridine (4-AP; Perreault and Avoli, 1991; Avoli et al, 2002; Heuzeroth et al, 2019). On the contrary, induction of epileptiform activity in human brain tissue ex vivo is less straightforward and subject to controversy.…”