title: Chronic proximal axonopathy in rats is associated with long-standing neurofilament depletion in neuromuscular junctions and behavioral deficits.
abstract: In rodents exposed to 3,3'-iminodipropionitrile (IDPN), neurofilaments (NFs) accumulate in swollen proximal axon segments; this also occurs in motor neurons of patients with amyotrophic lateral sclerosis. We hypothesized that early loss of NFs in neuromuscular junctions (NMJs) in IDPN proximal neuropathy would result in neuromuscular dysfunction and lead to neuromuscular detachment. Adult male rats were given 0 or 15 mmol/L IDPN in drinking water for up to 1 year. The IDPN-exposed rats dragged their tails and had impaired endurance in a grip test. Neuromuscular junctions and distal axons were examined in the levator auris longus muscle after 3, 6, 9, and 12 months. Neuromuscular junctions showed a progressive reduction in NF immunolabeling, which became undetectable in up to 70% of the NMJs after 12 months. Neurofilament labeling was also reduced in preterminal axons and in a more proximal axon level within the muscle. Triple-label analysis with antisyntaxin demonstrated that the terminals remained in place and usually contained a few minute NF bundles. Electron microscopy revealed the disappearance of terminal NFs, reduced content in synaptic vesicles, and accumulation of multilamellar bodies, but scant degeneration. Thus, IDPN proximal neurofilamentous axonopathy is associated with NF depletion in motor terminals; motor weakness and structural changes in the NMJs suggest impaired synaptic function despite long-term preservation of the NMJs.
authors.affiliation: From the Departament de Ciències Fisiològiques II, Universitat de Barcelona, and Institut d'Investigació Biomèdica de Bellvitge, Hospitalet de Llobregat, Barcelona (CS-M, JL); NEOMA Research Group, Departament de Ciències Mèdiques, Facultat de Medicina, Universitat de Girona, Girona (PB-V, EV); and Unitat d'Histologia i Neurobiologia, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Reus (NG), Spain.
authors.forename: Carla
authors.initials: C
authors.lastname: Soler-Martín
authors.forename: Pere
authors.initials: P
authors.lastname: Boadas-Vaello
authors.forename: Enrique
authors.initials: E
authors.lastname: Verdú
authors.forename: Neus
authors.initials: N
authors.lastname: Garcia
authors.forename: Jordi
authors.initials: J
authors.lastname: Llorens
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism* / Q000473:pathology* / Q000648:ultrastructure; D004195:Disease Models, Animal; D005552:Forelimb / Q000503:physiopathology; D007794:Lameness, Animal / Q000139:chemically induced / Q000473:pathology*; D008297:Male; D046529:Microscopy, Electron, Transmission; D016900:Neurofilament Proteins / Q000172:deficiency*; D009469:Neuromuscular Junction / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D020511:Neuromuscular Junction Diseases / Q000139:chemically induced / Q000473:pathology* / Q000503:physiopathology; D009570:Nitriles / Q000633:toxicity; D050765:Qa-SNARE Proteins / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D013997:Time Factors; D015837:Vestibular Diseases / Q000139:chemically induced / Q000473:pathology*
chemical_list: D016900:Neurofilament Proteins; D009570:Nitriles; D050765:Qa-SNARE Proteins; C044882:neurofilament protein L; C008110:3,3'-iminodipropionitrile