酸素電極法による局所脳循環に関する実験的研究—特に視床部循環を中心として

Experimental Study on Local Circulation in the Brain:Especially on the Thalamic Circulation by Polarographic Measurement of Oxygen Tension

I．緒言

　脳内局所循環，特に生命の重要中枢である視床部の血流動態を把握することは病態生理学上はもちろんのこと，臨床．上もきわめて重要である。しかし，脳循環に関しては，N20法^1）をはじめとする種々の測定法による多くの研究にもかかわらず，それらは脳全体か，あるいは頸動脈のレベルで論じられているものが多い。脳内直接測定法では，近年heat Clearance法^2）による局所循環測定の試みなどが報告されているものの，その研究にもなお問題が多い。

　著者は八木ら^3）により報告された銅エナメル線による酸素電極が，白金線による酸素電極に優るとも劣らず，生体組織に手軽に適用され，再現性も良く，高感度な，時間的応答性の良い血流計となりうるということに着目し，これを脳内局所組織に適用し，視床部循環および脳循環の自己調節磯構に関し研究を進め，興味ある知見を得たので報告する。

Local circulation of the brain was investigated by applying polarographic measurement of oxygen ten-sion using the enamelled Cu-wire to the cerebral cortex, the thalamus and the cerebellar cortex of the dog. The findings obtained are as follows :

1. It was characteristic that the local circulation of each part in the brain acted counterclockwise against the temporaly change of blood pressure when inspected the pressure-flow curve. This is due to the myogenic autoregulation of brain vessels.

Comparing to the cerebral cortex and the cerebellar cortex, the thalamus had smaller vascular resistance, which means its autoregulation is less active.

2. Autoregulation was obvious when local cir-culation of each part in the brain made hypertensive by blood transfusion showed no significant increase. This is because of the increased vascular resistance consequent on high cerebrospinal fluid pressure, and a myogenic factor.

3. In the hypotensive brain due to exanguination, only the least decrease was recognized in local cir-culation which was a myogenic reaction. Autoregula-tion in this case was less remarkable in the thalamus than that in other regions of the brain.

At the beginning of the periodic undulatory change of the blood pressure level, local circulation showed antergonistic with blood pressure, which is another function of autoregulation.

4. When CO₂ inhalation was attempted auto-regulation also funetioned to increase blood flow of the cerebral cortex and the cerebellar cortex while that of the thalamus would keep itself unchanged.

5. When C. S. F. pressure increase 400 mmH₂O blood flow in the cerebral cortex began to decrease. Blood flow in the thalamus was different in de-creasing in the anterior and the posterior part of it ; in the former it decrease at the C. S. F. pressure of around 600mmH₂O and the latter as soon as C. S. F. pressure began to increase.

Recovery of each blood flow was obtained at the C. S. F. pressure higher than that at which the de-crease of it occured

C. S. F. pressure-blood flow curve showed a convex curve at both the increase and decrease of C. S. F. pressure representing another evidence of auto-regulation.