辺縁系発作時における局所脳血流量—発作の伝播に伴う局所脳血流量の変化についての検討

REGIONAL CEREBRAL BLOOD FLOW IN LIMBIC SEIZURES INDUCED BY MICROINJECTION OF KAINIC ACID INTO AMYGDALA IN CATS

　抄録　てんかん発作時における神経細胞の興奮と，局所脳血流量との関係をより明確にするため，11匹のネコ一側扁桃核へのカイニン酸注入による辺縁系発作急性モデルを用いて，てんかん発作の伝播に伴う辺縁系および大脳皮質での血流変化を観察した。一側扁桃核にのみcontinuous multiple spikeの出現している時には，その扁桃核でのみ血流が約2倍に増加した。continuous multiple spikeが同側海馬に波及すると，扁桃核の局所脳血流量は平均90％，同側海馬では平均26％　局所脳血流量が増加したが，大脳皮質感覚運動領では変化はなかった。辺縁系発作がおき，発作波が大脳皮質に波及すると局所脳血流量は同側扁桃核，海馬および大脳皮質感覚運動領でそれぞれ平均89％，69％，18％増加した。発作間歇期での局所脳血流量はspike dischargeの少ないことを反映して各部でcontrol値と同じかやや高値を示した。発作焦点部は発作時には局所脳血流量が著明に増加する。発作波の伝播に伴い，各伝播部での局所脳血流量も，発作時に増加することが示された。

The relationship between neuronal epileptic activity and regional cerebral blood flow was studied by means of hydrogen clearance method (rCBF). Measurements of rCBF in the limbic structure and cerebral cortex were performed during limbic seizures induced by a microinjection of kainic acid to the left amygdala under concur-rent monitoring of polygraph. Pentobarbital (35 mg/kg, i. p.) anesthesia was induced and cats were artificially ventilated. Physiological parameters such as blood pressure, body temperature, PaO₂, PaCO₂ and HCO₃ were kept stable.

After fixation of the cat's head in a stereotaxic device, stainless screw electrodes were placed over bilateral anterior sigmoid gyrus so as to touch the dura mater for cortical EEG monitoring. Bipolar needle electrodes were stereotaxically placed to both amygdala and the left dorsal hippocampus. Platinum electrodes were stereotaxically placed to the left amygdala, dorsal hippocampus and senso-rimotor cortex. After measurements of control rCBF, a microsyringe was stereotaxically inserted into the left amygdala and kainic acid solution (2 ug) was injected. Polygraphic monitoring fol-lowed. Five to 30 minuted after kainic acid injec-tion, continuous multiple spikes appeared in the left amygdala. Forty to 120 minutes later, contin-uous multiple spikes transmitted to the left hippo-campus. Two to five hours later, limbic seizure occured. The limbic seizure lasted five to eight hours and interictal discharges appeared. Repeated measurements of rCBF were done.

In the left amygdala, rCBF increased about two-fold of the control immediately after development of continuous multiple spikes and remained in-creased as long as the seizure persisted. When continuous multiple spikes transmitted to the left hippocampus, rCBF in the left hippocampus in-creased to 126% of the normal but rCBF in the sensorimotor cortex was unchanged. During limbic seizures in which spike discharges were propagated to the left sensorimotor cortex, rCBF in the left hippocampus and left sensorimotor cortex increasedto 160% and 118% respectively. In the interictalphase, rCBF returned normal.

The result showed that rCBF increased nearlysimultaneously with the development of the seizurein the primary focus as well as the area whereseizure propagation was observed and returnednormal after disappearance of the seizure, andthat rCBF of the primary focus increased morethan that of the area of seizure propagation.