Kanic Acid-Induced Substantia Nigra Seizure : Behavior, EEG and Metabolism
Abstract number :
3.252
Submission category :
Year :
2000
Submission ID :
725
Source :
www.aesnet.org
Presentation date :
12/2/2000 12:00:00 AM
Published date :
Dec 1, 2000, 06:00 AM
Authors :
Atsushi Sawamura, Kiyotaka Hashizume, Katsunari Yoshida, Tatsuya Tanaka, Asahikawa Medical Coll, Asahikawa, Japan.
Rational : In order to clarify the role of substantia nigra pars reticulata (SNr) upon the development of epileptic seizure, kainic acid was injected into a unilateral SNr. After induction of seizure, behavior, EEG and local cerebral glucose utilization (LCGU) and local benzodiazepine receptor binding (125I-Iomazenil) were studied. Material and Methods : (1)Eight Wistar rats weighing 250-350 g were used. Under intraperitoneal pentobarbital anesthesia, a stainless-steel cannula was inserted stereotaxically into the left substantia nigra for KA injection. Behavior of the rats and EEG were continuously recorded for about 30 hours, and intermittently monitored following 1 month by the use of a video EEG monitoring system. (2)Ninety minutes after KA injection, 10 rats demonstrated status epilepticus. Then, 100?Ci/kg of [14C]2-deoxyglucose(2DG) was intravenously injected, and the rats were processed for autoradiographic study. In another 10 rats, 125I- Iomazenil was intravenously injected, and the rats were processed for autoradiographic study. Results : (1) Changes in behavior and EEG : On EEG, a secondary generalized seizure status was observed at about 70 minutes after KA injection. In Video, limbic seizure manifestations such as salivation were observed as a initial symptom and followed by rolling and generalized tonic seizures. (2) In 14C-deoxyglucose autoradiogram, increased LCGUs in the lateral septal nucleus, SNr, hippocampus, parietal cortex, ventroposterior lateral neclus of the thalamus, midbrain reticular formation, superior colliculus and inferior colliculus were observed. In Iomazenil autoradiogram, decreased LCGUs in the caudate nucleus, hippocampus, ventroposterior lateral neclus of the thalamus were observed. Conclusion : A microinjection of kanic acid into unilateral SNr resulted generalized seizure status. On the contrary, the decrease of benzodiazepine receptor binding was observed in hippocampi and thalamic nuclei. The result suggested that the substantia nigra played an important role in the secondary generalization in the substantia nigra seizure model due to decreased function of GABAergic projection system.