迷走神経反射に対するアドレナリンの効果 Effect of Adrenaline on Vagus Nerve Reflexes

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はじめに: 鼻副鼻腔手術後のガーゼ抜去時に患者が失神様の発作を起こすことがある. この状態は神経原性失神の1つである三叉・迷走神経反射が原因と言われている. 三叉神経が刺激されることにより, 迷走神経が反応して心拍数, 血圧が急激に低下する現象であるが, 我々は疼痛や緊張で上昇するアドレナリン (Adrenaline, 以下Adr. と略す) に着目し, ネコ10匹を使用して迷走神経反射におけるAdr. の効果を調べた.<BR>目的: 迷走神経刺激時にAdr. が脳血流に及ぼす影響を調べる.<BR>対象と方法: 実験には成猫10匹を用いた. 頸部で迷走神経を露出し, 末梢側に白金電極を装着した. さらに頭部を30度挙上した. コントロール群 (迷走神経を1分間電気刺激). Adr. +神経刺激群 (Adr. を30秒間静注した後, 迷走神経を1分間電気刺激) の2群に分け, 刺激前後の前庭神経核, 下オリーブ核, 小脳室頂核の脳血流量, 及び心拍数, 動脈圧を比較した. 脳血流の測定には水素クリアランス法を使用した.<BR>結果: コントロール群, Adr. +神経刺激群ともに刺激前と比較し, 刺激後は有意に脳血流量が低下した. さらに, 両群の脳血流量の変化を比較したところ, いずれの部位においてもAdr. +神経刺激群の方が, コントロール群と比較し有意に脳血流量が低下していた. 心拍数, 動脈圧についてはコントロール群は刺激後有意に低下したが, Adr. +神経刺激群では, より大きな脳血流量低下があったにもかかわらず有意な変化はなかった.<BR>考察: Adr. +神経刺激群ではAdr. のβ<SUB>2</SUB>作用で末梢欠陥抵抗が低下し, 迷走神経を電気刺激した際に, より大きな脳血流量低下が起きたのではないかと考えられた. この結果より疼痛や緊張で上昇したAdr.が, 三叉・迷走神経反射による脳血流量低下を増強しているのではないかと考えられた.

Introduction<BR>Dizziness or syncope may occur during treatment of nasal disease. These symptoms are considered imputable to the vagovagal reflex. which is partly involved in neurogenic syncope. In response to trigeminal nerve stimulation, the vagus nerve causes a sudden fall in heart rate and blood pressure.<BR>Elevation in blood adrenaline level during pain or tension was noted, and its effects on vagovagal reflexes were studied.<BR>Materials and Methods<BR>Ten cats were used in the experiment. The vagus nerve was exposed on the right side of the neck by making an incision in the trachea, and a platinum electrode was attached to the vagus nerve on nerve's distal side. The head was tilted a 30 degree angle. The cats were divided into control and adrenaline-treated groups, and changes in cerebral blood flow, heart rate, and arterial pressure were compared between the two groups after electric stimulation of the vagus nerve. Cerebral blood flow was measured by the hydrogen clearance method.<BR>1) Control group<BR>The vagus nerve was electrically stimulated for 1 minute.<BR>2) Adrenaline-treated group<BR>The vagus nerve was electrically stimulated for 1 minute following 30 seconds of intravenous administration of adrenaline.<BR>Results<BR>Cerebral blood flow was significantly decreased in both the control and adrenaline-treated groups after electric stimulation, but the decrease was signigicantly greater in the latter group at all sites of measurement. Whereas heart rate and arterial pressure were significantly decreased in the control group, these variables in the adrenalinetreated group showed no significant change despite the greater decrease in cerebral blood flow.<BR>Discussion<BR>Heart rate, blood pressure, and cerebral blood flow were all significantly decreased after electric stimulation of the vagus nerve. These changes were considered owing to a fall in blood pressure due to vasodilation resulting from bradycardia and a relative decrease in sympathetic nervous tension resulting from electric stimulation. On the other hand, in the adrenaline-treated group, neither heart rate nor blood pressure showed any significant change, but cerebral blood flow was significantly decreased at all sites of measurement despite an adrenaline load. This contradictory result may be accounted for by the powerful β<SUB>2</SUB>-activity of adrenaline. The greater decrease in cerebral blood flow in the adrenaline-treated than in the control group can be attributed to decreased peripheral vascular resistance by its β<SUB>2</SUB>-activity. In the field of otorhinolaryngology the trigeminal region is often involved in the treatment of nasal disorders so that vagovagal reflexes are often encountered. The results of this study counsels caution in the treatment involving the trigeminal region.

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  • 日本耳鼻咽喉科學會會報

    日本耳鼻咽喉科學會會報 102(7), 891-897, 1999-07-20

    一般社団法人 日本耳鼻咽喉科学会

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各種コード

  • NII論文ID(NAID)
    10005261188
  • NII書誌ID(NCID)
    AN00191551
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    00306622
  • データ提供元
    CJP書誌  CJP引用  J-STAGE 
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