The high seizure susceptibility in epileptic fowl is an autosomal recessive trait characterized in homozygotes by
seizures that occur spontaneously and in response to photic stimulation or
hyperthermia. Both of the latter stimuli can be used to evoke
seizures in
drug studies. Epileptic fowl have abnormal inter-ictal EEG activity. When exposed to photic stimulation spiking is apparent on the EEG at seizure onset.
Phenobarbital,
primidone,
phenytoin, and
valproic acid reduce seizure susceptibility at plasma concentrations approximating those used to control generalized and focal cortical
tonic-clonic seizures in humans.
Carbamazepine and the
benzodiazepines also reduce seizure susceptibility. These data indicate that epileptic fowl provide a useful model for generalized and focal cortical
tonic-clonic epilepsies.
Ethosuximide was inactive in epileptic fowl. However,
trimethadione had
anticonvulsant activity indicating that this model is only relatively specific for the above seizure types. When
seizures were evoked by
hyperthermia phenobarbital but not
phenytoin or
valproate reduced seizure susceptibility.
GABA (
gamma-aminobutyric acid), AOAA (amino-oxyacetic
acid) and
THPO (4,5,6,7-tetrahydroisoxazolo[4,5-c] pyridin-3-ole, a glial specific inhibitor of
GABA uptake) all have
anticonvulsant activity against
seizures evoked by photic stimulation in young chicks. These data indicate that this model may be particularly useful for studies of the
anticonvulsant activity of compounds designed to enhance GABAergic transmission.