大脳半球摘除ラット神経組織の生化学的変化—Neurotransmitterの動態について

NEUROCHEMICAL FINDINGS OF HEMISPHERECTOMIZED RATS

I．はじめに

　臨床的にinfantile hemiplegiaの患者に大脳半球摘除を行つた場合，片麻痺が術前よりむしろ軽快し，精神機能の面でも改善がみられるという事は良く知られた事実である。この現象は中枢神経系のplasticityと密接に関連していると思われる。我々は成熟ラットに大脳半球摘除を行い，術後行動面で明らかに回復する面がある事を観察した。このことは半球摘除されたラットに於ても残存中枢神経組織に何んらかの代償機構が働いていなければならないと考えられる。今回はシナプス部分の生化学的変化をみることを目的とした。即ち代表的なneu—rotransmitterとしてnoradrenaline（NA）serotonin （5HT）の量的変動とacetylcholine-esterase（AchE）の活性変化を経時的に検索すると共に，両アミン，及びcho—lineのsynaptosome分画への取り込みを検索したので報告する。

Clinical symptoms as hemiplegia and mental disturbances were often improved after the hemi-spherectomy of the affected side in the patient ofinfantile hemiplegia who had suffered from in-curable convulsion. The purpose of the present study is to clarify the mechanism of neural plasti-city on the basis of the biochemical findings.

In the present study on the hemispherectomized adult rat, acetylcholinesterase (AchE) activity, contents of serotonin (5HT) and noradrenaline (NA), and uptake of 5HT, NA and choline into synaptosome were assayed in discrete parts of the brain, and following results were obtained.

(1) AchE activity: In brain-stem of the left side which was contralateral to the side of hemi-spherectomy, the AchE activity decreased two weeks after the operation and recovered to the level of control one month after the operation. In brain stem of the other side, decrease inthe AchE activity was observed even one week and continued untill one month and recovered 6 months after the operation.

(2) Contents of noradrenaline (NA) and serotonin (5-HT): In all parts of brain examined, namely left cortex, hypothalamus, and medulla oblongata with spinal cord, the contents of NA and 5-HT decreased two to four weeks after the operation, then increased to or over the levels of the control.

(3) Uptake of ³H-choline by synaptosomal frac-tions: Statistically significant changes in the up-take activity of choline into the synaptosomal fraction were not observed in the left cortex nor in both sides of the brain stem 6 months after the operation.

(4) Uptake of ³H-NA and ³H-5HT by syn-aptosomal fractions: Increases in the uptake of NA and 5-HT were noted in the subcellular frac-tion derived from the brain stem but not in these fraction from the left cortex 6 months after the operation.

(5) Above mentioned observations were discussed in terms of plasticity of central nervous system.