20.500.12556/DiRROS-21723 Neuromuscular junction instability with inactivity morphological and functional changes after 10 days of bed rest in older adults The neuromuscular junction (NMJ) plays a key role in modulating muscle contraction,but the impact of short-term disuse on NMJ structure and function, particularly in older humans,remains unclear. This study aimed to investigate NMJ alterations following 10 days of horizontalbed rest in 10 older males (68.5 ± 2.6 years). Before and after bed rest, vastus lateralis musclebiopsies were obtained to evaluate NMJ morphology, intramuscular EMG (iEMG) was recordedto assess NMJ function and blood samples were collected to determine circulating C-terminal agrinfragment (CAF) concentration, a biomarker of NMJ remodelling. In a sub-cohort of six participantswho had NMJs in both pre- and post-bed rest biopsies, we observed altered NMJ morphology,including reduced overlap between NMJ terminals, as well as increased endplate area and peri-meter. CAF concentration was elevated after bed rest, suggesting ongoing NMJ remodelling. iEMGanalysis showed increased motor unit potential complexity and reduced firing rate. In addition,we observed impaired NMJ transmission, inferred from increased near-fibre jiggle and segmentjitter. These findings suggest that older male individuals are susceptible to NMJ remodelling andimpaired transmission with short-term disuse, providing valuable insights into the morphologicaland functional consequences of inactivity in an ageing population. Our study highlights theimportance of developing interventions for mitigating the detrimental consequences of inactivityon neuromuscular health in older adults, which they frequently experience following injury, trauma,illness or surgery. ageing C-terminal agrin fragment disuse electromyography motor unit NMJ unloading staranje C-terminalni agrinski fragment razbremenitev zaradi neuporabe elektromiografija nevromišična stična plošča (NMJ) razbremenitev true false true Angleški jezik Slovenski jezik © 2025 The Author(s) Neznano 2025-03-19 09:13:32 2025-03-19 09:13:32 2025-03-20 03:40:25 0000-00-00 00:00:00 2025 0 0 Nasl. z nasl. zaslona; Opis vira z dne 19. 3. 2025; str. 1-18 iss. Vol. 2025 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 2025-01-01 612.74 1469-7793 10.1113/JP288448 229471491 25_03_19_101_Simunic_229471491.pdf 25_03_19_101_Simunic_229471491.pdf 1 97FDF81E3AD7666F2B76CFED9EBA568C d1679f013547317f7cbb3e25fca1c2150fdc9a7334faf9fd022ac53afe1bcf61 44b9d6fa-049b-11f0-963a-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=31185 https://physoc.onlinelibrary.wiley.com/doi/10.1113/JP288448#support-information-section 1 0d697d82-049a-11f0-963a-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=31184 Znanstveno-raziskovalno središče Koper / Centro di Ricerche Scientifiche Capodistria 0 0 0