Development of epileptic activity induced by iron injection into rat cerebral cortex: electrographic and behavioral characteristics.

Unilateral injection of ferrous chloride solution into the rat sensorimotor cortex produced epileptic discharges in the electrocorticograms (ECoGs). The discharges were isolated spikes and spike and wave complexes, and the epileptic activity lasted for more than 12 months after the injection. Isolated spike activity often appeared on the left or right side of the cortex, whereas spike and wave complex activity appeared bilaterally. In rats showing dominant isolated spike activity in the secondary epileptic cortex, there was a deviation in somatosensory evoked potentials (SEPs). Rats showing isolated spikes and spike and wave complexes exhibited vibrissa tremors and head nodding. Rats showing only isolated spikes exhibited no abnormal behavior, but their convulsion thresholds to pentylenetetrazol were lowered. The results including ECoGs, SEPs, behavior and convulsion threshold were characterized with reference to the development of iron-induced epilepsy. The profiles of ECoG discharge activity and SEP configuration suggest that the process of iron-induced epilepsy consists of 3 stages.