A Caenorhabditis elegans assay of seizure-like activity optimised for identifying antiepileptic drugs and their mechanisms of action.
BACKGROUND
Epilepsy affects around 1% of people, but existing antiepileptic drugs (AEDs) only offer symptomatic relief and are ineffective in approximately 30% of patients. Hence, new AEDs are sorely needed. However, a major bottleneck is the low-throughput nature of early-stage AED screens in conventional rodent models. This process could potentially be expedited by using simpler invertebrate systems, such as the nematode Caenorhabditis elegans.


NEW METHOD
Head-bobbing convulsions were previously reported to be inducible by pentylenetetrazol (PTZ) in C. elegans with loss-of-function mutations in unc-49, which encodes a GABAA receptor. Given that epilepsy-linked mutations in human GABAA receptors are well documented, this could represent a clinically-relevant system for early-stage AED screens. However, the original agar plate-based assay is unsuited to large-scale screening and has not been validated for identifying AEDs. Therefore, we established an alternative streamlined, higher-throughput approach whereby mutants were treated with PTZ and AEDs via liquid-based incubation.


RESULTS
Convulsions induced within minutes of PTZ exposure in unc-49 mutants were strongly inhibited by the established AED ethosuximide. This protective activity was independent of ethosuximide's suggested target, the T-type calcium channel, as a null mutation in the worm cca-1 ortholog did not affect ethosuximide's anticonvulsant action.


COMPARISON WITH EXISTING METHOD
Our streamlined assay is AED-validated, feasible for higher throughput compound screens, and can facilitate insights into AED mechanisms of action.


CONCLUSIONS
Based on an epilepsy-associated genetic background, this C. elegans unc-49 model of seizure-like activity presents an ethical, higher throughput alternative to conventional rodent seizure models for initial AED screens.
['Wong|Shi Quan|SQ|', 'Jones|Alistair|A|', 'Dodd|Steven|S|', 'Grimes|Douglas|D|', 'Barclay|Jeff W|JW|', 'Marson|Anthony G|AG|', 'Cunliffe|Vincent T|VT|', 'Burgoyne|Robert D|RD|', 'Sills|Graeme J|GJ|', 'Morgan|Alan|A|']
D000818:Animals D000927:Anticonvulsants D017173:Caenorhabditis elegans D029742:Caenorhabditis elegans Proteins D003292:Convulsants D004195:Disease Models, Animal D004353:Drug Evaluation, Preclinical D005013:Ethosuximide D010433:Pentylenetetrazole D011963:Receptors, GABA-A D012640:Seizures
Caenorhabditis elegans Epilepsy Pentylenetetrazol Ethosuximide Calcium channel Anticonvulsant Drug screens GABA receptor