羅比卡因在興奮性細胞膜和血管平滑肌藥理學之研究

Pharmacological Studies on Excitable Membrane and Vascular Smooth Muscle by Ropivacaine

林佩玲(Pei-Lin Lin)

指導教授 ： 蔡明正

國立臺灣大學/醫學院/藥理學研究所/博士(2007年)

https://doi.org/10.6342/NTU.2007.10365

摘要

Ropivacaine是第一個由單純S型態的鏡像異構物發展出來的長效醯銨類局部麻醉劑，其結構和麻醉效果和bupivacaine類似，提供在中樞神經系統、心臟血管系統方面較低的毒性，且具有感覺與運動阻礙分離明顯的特性。自從1996年上市以來，ropivacaine普遍使用於硬膜外麻醉、周圍神經阻斷麻醉、術後止痛、無痛分娩等，但仍有不少因為使用ropivacaine不慎而引起全身痙攣等中樞神經系統中毒以及心跳停止等心血管系統中毒的案例發生。本文除了利用蝸牛的神經元尋找ropivacaine誘發神經毒性的可能作用機轉，另一部份則觀察ropivacaine對天竺鼠的胸主動脈環的反應以了解ropivacaine對血管張力的影響。
本文在探討ropivacaine誘發神經毒性的可能作用機轉，乃利用非洲大蝸牛(Achatina fulica Ferussac) 食道下神經節(suboesophageal ganglion)中的RP4神經元為實驗標本，以一般藥理學與電生理學的方法，觀察ropivacaine及其他藥物對非洲大蝸牛食道下神經節RP4神經元的膜電位、振福、頻率的改變。在正常生理溶液灌流下，RP4神經元會產生自發性單一規則的動作電位，當細胞外投予ropivacaine (900μM)，RP4神經元的自發性動作電位會由單一規則性的形式轉變成猝發性(bursting)的形式，此猝發性的動作電位 (burst firing) 是可逆性的，且無法被(1) 投予prazosin (100 μM)、propranolol (100 μM)、atropine (1 mM)、d-tubocurarine (100 μM)，(2) 事先灌流缺鈣生理溶液 (Ca2+-free solution)，(3) 事先投予PKA 抑制劑H89 (10μM)，(4) 事先投予PKC抑制劑chelerythrine chloride (10 μM)所抑制。代表ropivacaine所引起動作電位的猝發現象並非經由(1)腎上腺素受器及膽鹼素受器，(2) 細胞外鈣離子，(3) PKA相關的訊息傳遞路徑，(4) PKC相關的訊息傳遞路徑。但動作電位的猝發現象卻可以被(1) 事先投予PLC 抑制劑U73122 (30 μM)，(2) 投予neomycin (3.5 mM)，(3) 投予高鎂生理溶液 (30 mM)所抑制。顯示猝發現象可能與PLC的活化有關，也就代表ropivacaine誘發的神經毒性很可能與PLC的活性的大小有密切的關連。
觀察ropivacaine對天竺鼠胸主動脈環的反應以了解ropivacaine對血管平滑肌的影響。利用不同濃度的ropivacaine分別作用於保存內皮細胞和去除內皮細胞的主動脈環以觀察張力的改變，結果發現ropivacaine對保存內皮細胞的主動脈環無張力的變化，但是ropivacaine對去除內皮細胞的主動脈環卻有收縮的反應，代表內皮細胞對ropivacaine造成血管放鬆的反應佔有重要的地位。比較不同濃度的ACh 或ropivacaine在保存內皮細胞且受到phenylephrine (10-5 M)先行處理的主動脈環的張力變化，結果顯示ropivacaine的放鬆作用遠大於ACh。先用yohimbine (α-adrenergic antagonist)、propranolol (β-adrenergic antagonist)、atropine (cholinergic antagonist)等抑制劑分別將主動脈環灌流20分鐘，再用phenylephrine預先處理，之後再給予各種不同濃度的ropivacaine觀察其反應，結果發現yohimbine、propranolol、atropine三者皆不會影響ropivacaine對血管的放鬆反應，代表ropivacaine引起保存內皮細胞的主動脈環的血管放鬆反應，應與α-、β-腎上腺素受器及膽鹼素受器無關。先用indomethacin將主動脈環灌流20分鐘，再用phenylephrine預先處理，之後再給予不同濃度的ropivacaine觀察張力的改變，結果發現indomethacin可以明顯減少ropivacaine (3 x10-4到10-2 M) 對血管的放鬆反應，代表ropivacaine對保存內皮細胞主動脈環的血管放鬆反應與prostaglandin system有關。另外用L-NAME(NOS抑制劑)、ODQ (guanylyl cyclase抑制劑)、methylene blue (既是NOS抑制劑，也是guanylyl cyclase抑制劑)等分別將主動脈環灌流20分鐘，再用phenylephrine預先處理，之後再給予各種不同濃度的ropivacaine來觀察張力變化，結果發現L-NAME、ODQ、methylene blue三者皆可以明顯減少ropivacaine (3 x10-4到10-2 M)對血管的放鬆反應，代表ropivacaine對保存內皮細胞的主動脈環的血管放鬆反應與NO-cGMP pathway有關。換句話說，ropivacaine可以引發保存內皮細胞的主動脈環血管放鬆，而造成血管放鬆的機制，應與prostaglandin system和NO-cyclic GMP pathway有密切的關係。
總結此論文，ropivacaine雖然具有較高的安全性，一旦使用不慎，仍可能發生中樞神經或心血管系統方面嚴重的併發症，在中樞神經系統方面，ropivacaine所誘發的神經毒性很可能與PLC的活性的大小有密切的關連，或許可以用PLC 抑制劑處理或避免全身性痙攣的發生；在心血管系統方面，ropivacaine對含有內皮細胞的主動脈環，可能經由NO–cGMP和prostaglandin system的途徑引發血管放鬆的反應，提供臨床上因大量血管吸收可能引發血液動力改變(hemodynamic change)之參考。

關鍵字

羅比卡因 ； 中樞神經元 ； 痙攣 ； 內皮細胞 ； 血管放鬆

並列摘要

Ropivacaine, a pure S-enantiomer, is a long-acting amide local anesthetic agent. It is similar to bupivacaine in chemical structure and anesthetic action. Ropivacaine produces sensory-motor differential blockade and results in less cardiac and neurotoxicity than bupivacaine. Since its clinical introduction in 1996, it is widely used for epidural anesthesia, nerve blockade, postoperative analgesia, and painless labor. Several reports have documented ropivacaine-induced convulsion and some have reported cardiotoxicity, such as cardiac arrest. The purposes of the study are as follows: (1) to investigate the possible mechanisms of ropivacaine-induced neurotoxicity using the central neuron of snail; (2) to identify the effects of ropivacaine in vasomotor tone on endothelium-dependent guinea pig aorta.
The effects of ropivacaine on a central neuron (RP4) of giant African snail (Achatina fulica Ferussac) were recorded by pharmacological and electrophysiological technique. The RP4 neuron showed spontaneous firing of action potential. Extra-cellular application of ropivacaine (900μM) reversibly elicited bursts of potential on RP4 neuron. The bursts of potential elicited by ropivacaine were not blocked after administration of (1) prazosin (100 μM), propranolol (100 μM), atropine (1 mM), d-tubocurarine (100μM), (2) pretreatment with calcium-free solution, (3) pretreatment with H89 (10μM), and (4) pretreatment with chelerythrine (10 μM). The bursts of potential elicited by ropivacaine were blocked by pretreatment with U73122 (30 μM) or additions of neomycin (3.5 mM) or high magnesium solution (30 mM). Ropivacaine-elicited bursts of potential are closely associated with the phospholipase C activity, not directly related to (1) adrenergic or cholinergic receptors, (2) the extra-cellular calcium ion fluxes, (3) the PKA activity and (4) the PKC activity in the neuron. It suggests ropivacaine-induced neurotoxicity may be associated with phospholipase C activity.
Isolated guinea pig aortic rings were suspended for isometric tension recordings. Ropivacaine (3 x 10-4 to 10-2 M) produced vasoconstriction in endothelium-denuded aortic rings, whereas no such response was observed in aortic rings with intact endothelium. In phenylephrine (10-5 M) precontracted intact aortic rings, ropivacaine induced a greater degree of vasorelaxation than acetylcholine. Yohimbine (10-6 M), propranolol (10-6 M) and atropine (10-6 M) all failed to affect the relaxation responses induced by ropivacaine. Pretreatment with indomethacin (10-5 M; cyclooxygenase inhibitor), L-NAME (10-3 M; nitric oxide synthase inhibitor), methylene blue (10-6 M; nitric oxide synthase and soluble guanylyl cyclase inhibitors) or ODQ (10-5 M; soluble guanylyl cyclase inhibitor), significantly decreased ropivacaine-induced relaxation of endothelium intact aortic rings (3 x 10-4 to 10-2 M). Ropivacaine elicits an endothelium-dependent vasorelaxation in the phenylephrine precontracted aortic rings via the nitric oxide (NO)-cyclic GMP pathway and the prostaglandin system.
In conclusion, ropivacaine is a safer local anesthetic agent compared with bupivacaine. After accidental intravascular administration, ropivacaine-induced CNS and cardiovascular toxicity will be developed. Ropivacaine-induced neurotoxicity is highly associated with PLC activity and PLC inhibitor may offer a novel therapeutic approach for managing local anesthetic-induced convulsion or other transient neurological toxicity. Ropivacaine elicits an endothelium-dependent vasorelaxation in the phenylephrine precontracted aortic rings via the nitric oxide -cyclic GMP pathway and the prostaglandin system.

並列關鍵字

Ropivacaine ； Central neuron ； Convulsion ； Endothelium ； Vasorelaxation

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