• Sangseok Lee, Hong-Seuk Yang, Tomoki Sasakawa, Mohammed A S Khan, Ashok Khatri, Masao Kaneki, and J A Jeevendra Martyn.
• 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 1;120(1):76-85.

BackgroundMature 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.MethodsMice 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.ResultsImmobilization (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.ConclusionsIneffectiveness 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.

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