Effects of whole-body x-irradiation on electroshock seizure responses in developing rats

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Abstract
Electroshock seizure responses were studied in control and irradiated rats between 8 and 55 days of age. Experimental animals were exposed to 500 r whole-body X-irradiation 2 days postnatally. In maturing rats seizure patterns produced by brain stimulation with 50 ma current appear in sequence: hyperkinesia, clonus, forelimb flexion, forelimb extension followed by hind limb flexion, and hind limb flexion followed by hind limb extension. In irradiated rats full flexor-extensor seizure pattern appeared in 50% of animals at 13 days of age, 3 days earlier than in controls. Extension was longer and flexion, clonus, and total seizure were shorter in irradiated than in controls. In both groups durations of clonus and total seizure were related inversely to durations of extension. Duration of flexion decreased and duration of extension increased up to 22nd day of age in all animals. This indicates increased neuronal activity as the brain matures. Also thresholds for minimal electroshock convulsions decreased up to 22nd day of age, further indicating increased brain activity with maturation. Thresholds were significantly lower in irradiated rats than in controls.