マウス大脳の皮質と髄質の毛細血管の相異

STRUCTURAL DIFFERENCES BETWEEN CAPILARIES IN CORTEX AND THOSE IN THE MEDULLA OF THE MOUSE BRAIN

Ｉ．はじめに

　血液脳関門（Blood-brain barrier，以下B．B．B．と略す）については多数の研究があり^{2）6）10）16）18）19）20）21）}，実験的事実が集積されてきた。また臨床神経学の分野でも薬剤の中枢神経に対する作用等から関心がもたれている。

　しかし，今日に至ってもB．B．B．の解明は完全ではない。関門とは二つの成分の物質の移動，すなわち血漿と血管外成分との間の物質の透過をいうのであつて，形態学的検地から毛細血管内皮細胞説，基底膜説，そしてグリア細胞説が述べられているが，詳細については不明である。脳の場合，他の組織に比較して，溶質の交換速度が遅いということであつて，B．B．B．はあくまで，量的，相対的な問題である。それらをうらづける根拠として，Maynardら^12）の白ネズミ大脳皮質の血管の電顕的観察があるが，大脳の皮質と髄質との電顕的比較はみられない。

Comparing the capillaries in the cortex with those in the medulla of the mouse brain, there exist several differences :

1) The capillary lumen in the cortex shows irregu- lar outline, but relatively smooth in the medulla.

2) In the cortex endothelium is very thin and the endothelial cells show high density and have less well developed organelles except for riboso- mes and vesicles. In the medulla they show low density and have well developed Golgi apparatus and mitochondria and a few vesicles.

3) In the cortex the basement membrane (basal lamina) shows low density, is thicker than in the medulla, and shows sometimes multiple layer. In the medulla it shows almost constant thick- ness of averaging 700 Å.

4) Outside of the capillaries, the area occupied by the end feet of the astrocyte is wide in the cortex, but narrow in the medulla. In the latter neuropile are sometimes adjacent to the base- ment membrane.

5) Based on the findings of the present study and others, it is concluded that in the brain the exchange of substances between the blood and the tissue performs slowly compared with other vessels and thus it may be natural that the consept of "blood-brain barier" is taken away.