Secondary generalization in kainic acid-induced focal seizures in unanesthetized cats

Seizure propagation was studied with different seizure models induced by a kainic acid (KA) microinjection in nonanesthetized cats. These seizures were characterized with a focal onset of seizures followed by secondarily generalized seizures. The mesencephalic reticular formation (MRF) played an important role when an epileptogenic focus was located in a unilateral amygdala, hippocampus, thalamus or visual cortex. When the focus was located in a unilateral lateral geniculate body, a fast, synchronous and bidirectional propagation was observed in the sensorimotor cortex (SMC) and MRF. Brain stem seizure (generalized tonic seizure) was elicited by the KA injection into MRF. The EEG of generalized seizure was characterized by the propagations of seizure activities of MRF immediately to the bilateral SMC and thalamus. The results suggested that MRF participated actively in the generalization of the KA-induced seizures.