プロスタグランディンと脳循環—プロスタグランディンのネコ脳底動脈に対する影響

PROSTAGLANDINS AND CEREBRAL CIRCULATION:EFFECTS OF PROSTAGLANDINS A1, E1, E2AND F2α ON THE FELINE BASILAR ARTERY

　プロスタグランディンProstaglandins, PGは，生体内に正常でも存在する5員環を含むC₂₀の脂肪酸pro—stanoic acidを基本構造とし，これに二重結合，_-OH基，＝O基などが導入されてできる誘導体の総称で（第1図），多種多様の生理学的作用をもち，また多くの病的状態の発生に関与することが知られている^11,12,23）。

　心・脈管系に対する作用としては，E系PG （PGE₁，PGE_2）はヒトを含む各種の動物のいろいろの組織・器官血管床に対して強い拡張作用をもつ。PGE₁，　PGE₂を静脈内に投与すると，心拍数，心搏出量は増加するが，強い血管拡張のため動脈圧は普通低下する_{1,2,3,5,6,13）}。

Effects of intravenous administration and topical application of prostaglandins (PG) A₁, E₁, E₂ andF_2α, on the exposed basilar artery were studied in cats. Intravenous injection of PGF_2α, caused vaso-constriction, whereas intravenous administration of PGA₁, PGE₁, and PGE₂ resulted in vasodilatation, of the basilar artery. The change in the arterial diameter seemed to be independent of the systemic responses to prostaglandins.

PGA₁, PGE₁, PGE₂, and PGF₂, all caused con-striction of the basilar artery when applied topical-ly. The vasoconstriction seemed to be increased in degree and incidence with the addition of fresh blood to the topically applied PGFF_2αand PGE₂. Intravenous administration of PGE₂ in dosage of 20μg/kg showed a slight alleviating effects on the vasoconstriction induced by topical application of fresh blood.

Role of prostaglandins on the homeostatic mecha-nism of cerebral circulation, and on the genesis of certain pathologic cerebral vascular events such as cerebral arterial spasm and migraine syndrome, was briefly discussed.