各種aspartatesの中枢神経系に対する作用に関する研究

EFFECTS OF ASPARTATES ON BRAIN ACTIVITY OF THE CAT

I．はじめに

　aspartic acidやN-acetyl-L—aspartic acidは他のアミノ酸とともに高等動物の脳に高濃度に存在する^{2）16）17）}。また，L-aspartic acidは痙攣時における脳内glutamic acidの減少を防止するといわれ^20），N-methyl-DL-aspartic acidは逆に動物に疾走発作を誘発することも知られている^5）14）。玉木ら^18）は中枢興奮剤によるマウスの痙攣にK，Mg-aspartateが抑制的に働くことを報告した。aspartic　acidあるいはその塩類が脳代謝にいかなる生理的役割をはたしているか，また静脈内に投与されたaspartateが脳血液関門を通過して中枢神経系に直接作用するか否かは問題である。しかし，いずれにしても，aspartic acidやaspartateが中枢神経系の機能に何らかの影響を与えることが推察できる。一方，aspartateは，血中ammonia量の増加を抑制する作用^{8）9）10）13）18）}およびammoniaの毒性を防止する作用^{8）9）10）}があり，近時，細胞活性剤，疲労回復剤として広く用いられている^{7）9）10）18）}。ゆえにas—partateが疲労を防止し，人の作業効果を上昇させる背後に，aspartateのammonia代謝に対する作用のみならず，それが中枢神経系に対して作用する可能性も無視するわけにはいかない。

　本実験は，猫を用い，aspartate投与により誘発される動物行動とそのさいに出現する脳波変化を記録し，各種aspartatesが中枢神経系の活動にいかなる影響を及ぼすかを検討し，その作用機序の一端を考察したものである。

In this experiment, effects of intravenous injection of aspartate on the brain wave and behavior of the cat were analysed. As the test materials, 10% Mg-aspartate (80mg/kg), 10% Na-aspartate (200mg/kg), 10% K, Mg-aspartate (65mg/kg) and 10% K-aspartate (50mg/ kg) were used respectively. The doses of each aspartate were all far less than the lethal doses for the cat, and they were solely injected with speed of 1 ml. per 15 seconds into the femoral vein.

Mg-aspartate, Na-aspartate and K, Mg-aspartate induced similar suppressive effects on the brain wave and animal behavior. After about 20 seconds of the application of these aspartates animals always showed licking, vomiting, slowing of respiratory movement, and they lost their muscle tension and finally became motionless. These effects continued for about five minutes or more and the animals gradually recovered from these effects within about 10 minutes. Among above described three aspartates, Mg-aspartate showed the strongest effects on behavior and the brain wave, and K, Mg-aspartate elicited rather only weak effects.

Both Mg-aspartate and Na-aspartate generally induced high voltage slow waves of the electroencephalograms of the cortex and deep parts of the brain. Such effects on the EEG were most dominant in the hyppocampus and amygdaloid nuclei, and a spectrum analysis revealed increasing of the wave elements of 2-4c/sec., 4-8c/ sec. and 8-13c/sec.

To the contrary, K-aspartate showed activating effects on both the brain wave and animal behavior within 15 seconds, and the animal always showed spastic rigidity of the limb muscles, enhanced respiration and the low voltage fast wave of the EEG.