DEVELOPMENT OF EPILEPTIC ACTIVITY IN EMBRYOS AND NEWLY-HATCHED CHICKSOF THE FAYOUMI MUTANT CHICKEN

The homozygous Fayoumi strain of epileptic chickens (Fepi) is affected by generalized convulsions consistently induced by intermittent light stimulation (ILS) and by intense sound. Although interictal EEG recor dings show continuous spikes and spike and wave activity, desynchroniz ation and flattening (DF) of the EEG are observed during seizures. We have studied development of the epileptic phenotype in embryonic (E) a nd posthatching (P) Fepi. As compared with those of chicken embryos of a normal strain, no differences were observed in the EEG before embry onic day (E) 16. Clearly differentiated spikes and spike and waves app eared at E17 in Fepi. Metrazol-induced EEG seizures were observed at E 16 in normal embryos and at E17 in Fepi. The Fepi showed some characte ristics: Spontaneous EEG seizure-like discharges also appeared at E17 but decreased toward hatching; visual or acoustic hyperexcitability de veloped at E20 together with evoked responses in normal chickens; desy nchronization of the EEG, typical of the epileptic seizure of the adul t, could be induced by ILS at E20, but ILS- or sound-induced generaliz ed motor seizures appeared at P1, a few hours after hatching. Results show that Fepi phenotype reaches full expression at P1, but the electr ic paroxysms are expressed earlier, paralleling synaptic maturation.