Mechanisms of anandamide-induced vasorelaxation in rat isolated coronary arteries
作者:Richard White、W -S Vanessa Ho、Fiona E Bottrill、William R Ford、C Robin Hiley
DOI:10.1038/sj.bjp.0704333
日期:2001.10
The cannabinoid arachidonyl ethanolamide (anandamide) caused concentration‐dependent relaxation of 5‐HT‐precontracted, myograph‐mounted, segments of rat left anterior descending coronary artery.
This relaxation was endothelium‐independent, unaffected by the fatty acid amide hydrolase inhibitor, arachidonyl trifluoromethyl ketone (10 μM), and mimicked by the non‐hydrolysable anandamide derivative, methanandamide.
Relaxations to anandamide were attenuated by the cannabinoid receptor antagonist, SR 141716A (3 μM), but unaffected by AM 251 (1 μM) and AM 630 (1 μM), more selective antagonists of cannabinoid CB1 and CB2 receptors respectively. Palmitoylethanolamide, a selective CB2 receptor agonist, did not relax precontracted coronary arteries.
Anandamide relaxations were not affected by inhibition of sensory nerve transmission with capsaicin (10 μM) or blockade of vanilloid VR1 receptors with capsazepine (5 μM). Nevertheless capsaicin relaxed coronary arteries in a concentration‐dependent and capsazepine‐sensitive manner, confirming functional sensory nerves were present. In contrast, capsazepine and capsaicin did inhibit anandamide relaxations in methoxamine‐precontracted rat small mesenteric arteries.
Relaxations to anandamide were inhibited by TEA (1 mM) or iberiotoxin (50 nM), blockers of large conductance, Ca2+‐activated K+ channels (BKCa). Gap junction inhibition with 18α‐glycyrrhetinic acid (100 μM) did not affect anandamide relaxations.
This study shows anandamide relaxes the rat coronary artery by a novel mechanism. Anandamide‐induced relaxations do not involve the endothelium, degradation into active metabolites, or activation of cannabinoid CB1 or CB2 receptors, but may involve activation of BKCa. Vanilloid receptor activation also has no role in the effects of anandamide in coronary arteries, even though functional sensory nerves are present.
British Journal of Pharmacology (2001) 134, 921–929; doi:10.1038/sj.bjp.0704333
以下是文本的中文翻译:
### 1. 方法
将大鼠左前降支冠状动脉段预先用 5-轻胺(5-HT)收缩,并将其固定在肌张力记录装置上,发现大麻素类物质花生四烯酸乙醇胺(即阿南达眯胺,anandamide)能引起浓度依赖性的血管舒张。这一舒张作用不依赖于血管内皮,不受脂肪酸酰胺水解酶抑制剂(如十八烯酰基三氟甲基酮,10 μM)影响,并可被阿南达眯胺的非水解衍生物(如甲基阿南达眯胺)所模拟。
### 2. 机制研究
阿南达眯胺引起的血管舒张作用可被大麻素受体拮抗剂 SR 141716A(3 μM)抑制,但不受更特异性的 CB1受体拮抗剂(如 AM 251,1 μM)或 CB2受体拮抗剂(如 AM 630,1 μM)影响。选择性 CB2受体激动剂(如棕榈酰乙醇胺)并不能引起预收缩冠状动脉的舒张。
### 3. 神经机制
阿南达眯胺的舒张作用不受感觉神经传递抑制剂(如辣椒素,10 μM)或香草酸 VR1受体阻断剂(如 N-乙酰基-2-苯基卡贝嗪,capsazepine,5 μM)的影响。然而,辣椒素却能在浓度依赖性和香草酸 VR1受体敏感性的作用下舒张冠状动脉,这证实了冠状动脉中存在功能性感觉神经。相反,香草酸 VR1受体阻断剂和辣椒素均能抑制甲基苯丙胺(methoxamine)预收缩的大鼠小肠系膜动脉的阿南达眯胺引起的舒张作用。
### 4. 电生理机制
阿南达眯胺引起的血管舒张作用可被大电导Ca2+激活的K+通道(BKCa通道)阻断剂(如TEA,1 mM)或伊贝毒素(iberiotoxin,50 nM)所抑制。但丙二醇-α-甘草酸酯(g parametrosin A, 100 μM,一种缝隙连接抑制剂)对阿南达眯胺的舒张作用无影响。
### 5. 结论
本研究发现,阿南达眯胺通过一种新颖的机制引起大鼠冠状动脉舒张。阿南达眯胺引起的舒张作用不涉及内皮细胞、活性代谢产物的生成,也不激活 CB1或 CB2受体,但可能涉及大电导Ca2+ 激活的K+ 通道(BKCa)的激活。此外,香草酸受体在冠状动脉中对阿南达眯胺的作用没有影响,尽管冠状动脉中存在功能性感觉神经。
*英国药理学杂志*(2001)**134**,921–929;doi:10.1038/sj.bjp.0704333