Effects of Cesium Bromide on the Electrically Induced Paroxysmal Discharges.
Abstract number :
1.258
Submission category :
Year :
2001
Submission ID :
168
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
H. Miyata, Bioengn., Soka Univ., Hachioji, Tokyo, Japan; M. Kitayama, Bioengn., Soka Univ., Hachioji, Tokyo, Japan; N. Saito, Bioengn., Soka Univ., Hachioji, Tokyo, Japan; M. Yano, Bioengn., Soka Univ., Hachioji, Tokyo, Japan; M. Taira, Bioengn., Soka Uni
RATIONALE: We have demonstrated that cesium chloride (CsCl) which is a blocker to the hyperpolarization-activated current (Ih) could significantly increase the paroxysmal discharge (PAD) threshold. Since it is well known that the bromides are classical AED, we have an idea that a simple inorganic compound such as cesium bromide (CsBr) would be a novel AED. In the present experiment, effects of CsBr on the electrically induced PAD were examined in the rabbit hippocampal CA1 region.
METHODS: Ten adult rabbits were used. They were anesthetized with pentobarbital sodium, immobilized with D-tubocurarine, and placed in a stereotaxic apparatus on artificial respiration. A pair of concentric injecting electrodes was introduced into each side of the hippocampal CA1 region and used for stimulating as well as recording hippocampal EEG. One (anterior right electrode) of them was also used for injection, of which tube was connected to the microsyringe filled with 10mM CsBr solution while connected to it containing saline in a control group. The injection was made with a speed of 50 [mu]l/min for 1 min. The stimulus train for PAD was 1 ms pulses of 50 Hz for 1 s.
RESULTS: The electrode locations of seven animals were identified in the stratum radiatum or lacunosum-moleculare of the CA1 region by the profile of hippocampal theta activity and by the histological result (a blue spot by ferrisyanide reaction). In the control group (n=7), the threshold for PAD was measured before and after injecting saline: they were 183[plusminus]8 [mu]A and 190[plusminus]8 [mu]A, respectively. In contrast, the threshold for PAD significantly (P[lt]0.02) increased to a level of 277[plusminus]6 [mu]A after injecting CsBr (n=7), while remaining almost the same level (187[plusminus]7 [mu]A) as the control before the injection.
CONCLUSIONS: In comparison with the data (n=6: 318[plusminus]10 [mu]A) of 10mM CsCl injection, effectiveness of CsBr on PAD threshold was lower than that of CsCl. Thus the Br ion seems not to involve in such an effect. It is concluded that CsBr can also increase the PAD threshold but the increment is based on the same mechanism (blocking Ih channel by Cs ion) which supports that Ih might play an important role in the seizure generation.
Support: This work is supported by GASR(C) of The Ministry of ESSC, Japan.