THE ROLE OF RETICULAR THALAMUS ON KAINIC ACID-INDUCED GENERALIZED SEIZURES IN RATS
Abstract number :
1.013
Submission category :
Year :
2002
Submission ID :
1578
Source :
www.aesnet.org
Presentation date :
12/7/2002 12:00:00 AM
Published date :
Dec 1, 2002, 06:00 AM
Authors :
Koichi Akaike, Shigeya Tanaka, Shin-ichi Imamura, Hideshi Tojo, Shin-ichiro Fukumoto, Morikuni Takigawa. Neuropsychiatry, University of Kagoshima, Faculty of Medicine, Kagoshima, Kagoshima, Japan; Neurosurgery, University of Kagoshima, Faculty of Medicine
RATIONALE: Previously we investigated the features of seizure induced by kainic acid (KA) microinjection into reticular thalamus (RT), and reported that RT might be another crucial epileptogenic site in rat forebrain as rivaled by area tempestas Gale et al. previously described. This study was designed to ellucidate the role of RT in KA-induced mesencephalic reticular formation (MRF) seizures in rats. A microinjection of KA into unilateral MRF resulted in recurrent generalized seizures in unrestrained rats (Tanaka et al., 1994).
METHODS: Twenty male Wistar rats underwent stereotactic implantation of electrodes in the left RT (LRT), the left MRF (LMRF), the bilateral dorsal hippocampus (LdH, RdH), and the bilateral sensorimotor cortex (LCx, RCx). For KA injection, stainless steel cannula was inserted into LMRF and LRT. After recovery from surgery, all rats received KA (2.0[mu]g) injection into LMRF. Five hours after KA injection, while rats were exhibiting generalized seizure status, 0.5[mu]l of phosphate-buffered saline solution (group 1, n=10) or 4% lidocaine hydrochloride (group 2, n=10) were injected into LRT. Electrophysiologic and behavioral observation was made in both group.
RESULTS: Two hours after KA injection, synchronous spike discharges were initially observed in all records. The rats showed immobilization. Three to five hours after KA injection, multiple synchronous spike discharges appeared, and the characteristics of these seizures were generalized tonic seizures followed by short clonic seizures. One hour after PBS injection in group 1, no electrophysiologic and behavioral change were seen. One hour after lidocaine injection in group 2, overall seizures became weak and transient, especially in the bilateral sensorimotor cortex and the LRT. Behaviorally, motor manifestations were markedly attenuated.
CONCLUSIONS: (1) Generalized seizure status was induced by KA injection into LMRF. (2) In the rats received lidocaine into LRT, multiple synchronous spike discharges became weak and transient, especially in the bilateral sensorimotor cortex and the LRT. Behaviorally, motor manifestations were attenuated. (3) These results suggested that RT might facilitate the development of generalized seizures induced KA microinjection.
[Supported by: Grant[ndash]in-Aid for Encouragement of Young Scientists from the Ministry of Education, Sciences, and Culture of Japan]