Oxyhemoglobin誘発による脳血管攣縮と交感神経因子（第2報）—Denervation supersensitivityよりの検討

EXPERIMENTAL CEREBRAL VASOSPASM INDUCED BY OXYHEMOGLOBIN AND THE SYMPATHETIC NERVOUS SYSTEM (PART 2):AN INVESTIGATION INTO DENERVATION SUPERSENSITIVITY

　抄録　Oxyhemoglobinにより誘発されるネコ脳底動脈の収縮と血管交感神経にみられるdenervationsupersensitivityのかかわりについて検討した。実験はnoradrenalinとoxyhemoglobinにより誘発される脳底動脈の収縮を直視下に観察し，reserpine, 6-hydroxydopamine （6-OHDA）投与によるchemicaldenervationまたは両側上頸神経節切除によるsurgical denervationを施行した群と非処置群における差異を比較した。denervation群においてnoradrenalinによる収縮は，非処置群に対し明らかに反応性が増大したが，oxyhemoglobinによる収縮はreserpine処置群でやや増大の傾向は認めるものの有意の変化は観察されなかった。6-OHDAおよび上頸神経節切除群では，むしろ減弱の傾向すら認められた。即ち，クモ膜下出血後に脳血管壁がdenervateされた状態にあったとしても，oxyhemoglobinにより誘発される脳血管攣縮においてdenervation supersensitivityが本病態の増悪に関与する可能性は小さいものと考えられた。

The pathological mechanism of cerebral vasospasm following subarachnoid hemorrhage has not been well clarified until now. There have been reports that denervation supersensitivity in cerebral vesselsoccurring after subarachnoid hemorrhage may pos-sible play a role in the appearance of cerebral vasospasm. On the other hand, we have accepted that oxyhemoglobin (Oxy-Hb) is an important spas-mogenic substance.

In the present study, we investigated the effect of chemical denervation (reserpine or 6-hydroxy-dopamine : 6-OHDA) and surgical denervation (bi-lateral superior cervical ganglionectomy : SCG) on the constrictive sensitivity of cat basilar arteries to noradrenalin (Nor) and oxyhemoglobin (Oxy-Hb) in situ.

Method : Adult cats were anesthetized with intra-muscular pentobarbital and maintained on a respi-rator through a tracheostomy. By the transclival approach, the basilar artery was exposed. A cannule was then inserted into the subarachnoid space, and through it, Oxy-Hb and Nor were injected. The sequential changes in caliber of the basilar artery were measured using photography. SCG was done 7 days before the application of Nor or Oxy-Hb and 14 days before application of Oxy-Hb. Pretreatment with reserpine was done as follows : 1 mg/kg of reserpine was injected subcutaneously once each day for 2 days. On the following day, the sensitivity of the basilar arteries to Nor or Oxy-Hb was assessed. Pretreatment with 6-OHDA was done as follows : 5 mg of 6-OHDA was dissolved in 1.0 ml of artificial CSF, and then injected into the cisterna magna. Seven days later, Nor or Oxy-Hb was applied.

Results : Pretreatment with reserpine tended to increase the vasoconstriction induced by 10^-7~10^-4M of Nor and the constriction induced by 10^-3M of Nor was increased statistically (P<0.05). Cisterns magna injection of 6-OHDA tended to increase the vasoconstriction induced by Nor. SCG tended to increase the vasoconstriction induced by 10^-7~10^-4M of Nor and at a dose of 10^-3M of Nor, the constric-tion of the basilar arteries was increased statistically (P<0.05). However, pretreatment with reserpine, 6- OHDA and SCG did not increase the vasoconstriction induced by Oxy-Hb.

These results lead us to suggest that denervation supersensitivity does not participate in the vasocon-striction induced by Oxy-Hb.