From Massachusetts General Hospital, Shriners Hospitals for Children®, Boston, Massachusetts, and Harvard Medical School, Boston, Massachusetts (S.L., H.-s.Y., T.S., M.A.S.K.); the Peptide Core Facility, Massachusetts General Hospital (A.K.); the Signal Transduction Laboratory, Massachusetts General Hospital, and Harvard Medical School (M.K.), the Clinical and Biochemical Pharmacology Laboratory, Massachusetts General Hospital, Shriners Hospitals for Children®, and Harvard Medical School (J.A.J.M.). Current positions: Sang-gye Paik Hospital, College of Medicine, In-Je University, Seoul, South Korea (S.L.), Department of Anesthesiology, Asan Medical Center, University of Ulsan, Seoul, South Korea (H.-s.Y.), Asahikawa University, Asahikawa, Japan (T.S.).
Anesthesiology. 2014 Jan;120(1):76-85. doi: 10.1097/ALN.0000000000000025.
Mature acetylcholine receptor (AChR) isoform normally mediates muscle contraction. The hypothesis that α7AChRs up-regulate during immobilization and contribute to neurotransmission was tested pharmacologically using specific blockers to mature (waglerin-1), immature (αA-OIVA), and α7AChRs (methyllycaconitine), and nonspecific muscle AChR antagonist, α-bungarotoxin.
Mice were immobilized; contralateral limbs were controls. Fourteen days later, anesthetized mice were mechanically ventilated. Nerve-stimulated tibialis muscle contractions on both sides were recorded, and blockers enumerated above sequentially administered via jugular vein. Data are mean ± standard error.
Immobilization (N = 7) induced tibialis muscle atrophy (40.6 ± 2.8 vs. 52.1 ± 2.0 mg; P < 0.01) and decrease of twitch tension (34.8 ± 1.1 vs. 42.9 ± 1.5 g; P < 0.01). Waglerin-1 (0.3 ± 0.05 μg/g) significantly (P = 0.001; N = 9) depressed twitch tension on contralateral (≥97%) versus immobilized side (approximately 45%). Additional waglerin-1 (total dose 1.06 ± 0.12 μg/g or approximately 15.0 × ED50 in normals) could not depress twitch of 80% or greater on immobilized side. Immature AChR blocker, αA-OIVA (17.0 ± 0.25 μg/g) did not change tension bilaterally. Administration of α-bungarotoxin (N = 4) or methyllycaconitine (N = 3) caused 96% or greater suppression of the remaining twitch tension on immobilized side. Methyllycaconitine, administered first (N = 3), caused equipotent inhibition by waglerin-1 on both sides. Protein expression of α7AChRs was significantly (N = 3; P < 0.01) increased on the immobilized side.
Ineffectiveness of waglerin-1 suggests that the twitch tension during immobilization is maintained by receptors other than mature AChRs. Because αA-OIVA caused no neuromuscular changes, it can be concluded that immature AChRs contribute minimally to neurotransmission. During immobilization approximately 20% of twitch tension is maintained by up-regulation of α-bungarotoxin- and methyllycaconitine-sensitive α7AChRs.
成熟的乙酰胆碱受体（AChR）亚型通常介导肌肉收缩。通过使用特定的成熟（瓦林林-1）、不成熟（αA-OIVA）和 α7AChR（甲基乌头碱）以及非特异性肌肉 AChR 拮抗剂α-银环蛇毒素的阻滞剂进行药理学测试，检验了α7AChR 在固定过程中上调并有助于神经传递的假设。
将小鼠固定；对侧肢体为对照。14 天后，对麻醉小鼠进行机械通气。记录双侧胫前肌神经刺激收缩，通过颈静脉序贯给予上述阻滞剂。数据为平均值±标准误差。
固定（N=7）导致胫前肌萎缩（40.6±2.8 与 52.1±2.0mg；P<0.01）和抽搐张力下降（34.8±1.1 与 42.9±1.5g；P<0.01）。瓦林林-1（0.3±0.05μg/g）显著（P=0.001；N=9）抑制对侧（≥97%）与固定侧（约 45%）的抽搐张力。另外的瓦林林-1（总剂量 1.06±0.12μg/g 或正常情况下约 15.0×ED50）不能使固定侧 80%或更大的抽搐完全抑制。不成熟的 AChR 阻滞剂αA-OIVA（17.0±0.25μg/g）对双侧张力无影响。给予α-银环蛇毒素（N=4）或甲基乌头碱（N=3）可使固定侧剩余抽搐张力抑制 96%或更高。首先给予甲基乌头碱（N=3）可使瓦林林-1在两侧产生等效抑制。固定侧的α7AChR 蛋白表达显著增加（N=3；P<0.01）。
瓦林林-1 无效表明，固定期间的抽搐张力由成熟 AChR 以外的受体维持。由于αA-OIVA 未引起神经肌肉变化，可以得出结论，不成熟的 AChR 对神经传递的贡献最小。在固定期间，约 20%的抽搐张力由上调的α-银环蛇毒素和甲基乌头碱敏感的α7AChR 维持。
