Fig. 4: The activity of nicotinic acetylcholine receptor (nAChR) prevents atrophy of skeletal myofibers.

Primary cultures of myofibers from flexor digitorum brevis (FDB) muscle were used. a Membrane permeability was measured in time-lapse experiments evaluating ethidium (Etd⁺) uptake performed after 24 h of culture. Myofibers were cultured under control conditions (white), or treated with 15 µM pancuronium (Pcu; green). b N = 4; six myofibers recorded in each independent experiment, each value is the mean ± SEM. ***p < 0.001, for effect of Pcu compared with Control by Student’s t test. c Resting membrane potential (RMP) was evaluated at 24 h of culture. Myofibers were cultured under control conditions or after treatment with 15 µM Pcu. N = 5; at least 20 myofibers recorded in each independent experiment. *p < 0.05, for effect of Pcu compared with Control by Student’s t test. d Upper images, intracellular Ca²⁺ signals (340/380) and, lower images, Na⁺ signals were recorded at 24 h of culture with FURA-2 and SBFI, respectively. The colored scale to the right of the panels depicts the color shifts from blue to green as the dye is bound to Ca²⁺ or Na⁺. Parallel cultures were treated with 15 µM Pcu and 24 later the Ca²⁺ and Na⁺ signals were evaluated. Scale bar: 50 µm. e Proposed model.