BASIC RESEARCH ON THE MECHANISM OF GENERALIZATION OF SEIZURES USING A BRAIN STEM FOCUS MODEL.

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1. Under pentobarbital anesthesia, stereotaxic operation was carried out in ten cats and a cannula was placed into the right mesencephalic reticular formation(MRF). Bipolar electrodes were placed in the MRF and the thalamus. About 8 days after recovery from the operation, 1-2 mug of kainic acid solution was injected during the animal was awake and resting. Video-EEG monitorings followed. A focal MRF seizures were initially noted at the injected site of the MRF about 30 min after the injection. However, no behavioral change was noted at this stage. These seizures reappeared every 5 minutes and developed. The seizures propagated progressively to bilateral thalamus and sensori-motor cortex (SMC). In this stage, cats demonstrated generalized tonic seizures. However, seizures became less frequent and subsided within 24 hours after the injection. The behavior of the animals also became normal afterwards. Pathological study revealed a small necrosis at the injected site of the MRF.2. Evoked potential study was made between MRF, thalamus and SMC. Rapid evoked responses (within 5 msec) were recorded at the thalamus and SMC. The results suggested that MRF played an important role in the mechanism of the secondary generalization of the seizures.3. A stereotaxic operation was carried out and a cannula was placed in the right MRF in rats. About 8 days after the surgery, kainic acid(0.5 mug) was injected into the MRF. Each injection resulted in generalized tonic seizures. An autoradiographic study using 14C-deoxyglucose was made during generalized tonic seizure status. The result disclosed hypermetabolic areas of the local cerebral glucose utilization at the injected site of the MRF as well as bilateral thalamus and SMC, which suggested immediate seizure propagation from MRF to bilateral thalamus and SMC.The results suggested a strong participation of MRF in the mechanism of generalized tonic seizure and secondary generalization of the seizures.