Analysis of neuromuscular junctions and effects of anabolic steroid administration in the SOD1G93A mouse model of ALS

Several lines of evidence indicate that neuromuscular junction (NMJ) destruction and disassembly is an earlyphenomenon in amyotrophic lateral sclerosis (ALS). Here we analyzed by confocal and electron microscopy theNMJ structure in the diaphragm of SOD1G93A mice at symptom onset. In these mice, which provide a model forfamilial ALS, diaphragm denervation (~50%) as well as gastrocnemius denervation (~40%) was found. In addition,thesizeofthesynapticvesiclepoolwasreducedandalterations of mitochondria were observed in approximately40% of the remaining presynaptic terminals. Chronic treatment of SOD1G93A mice with the anabolic steroidnandrolone during the presymptomatic stage preservedthe diaphragm muscle mass and features indicative ofsynaptic activity. These features were represented by the number of vesicles docked within 200 nm from thepresynaptic membrane and area of acetylcholine receptor clusters. Structural preservation of mitochondria wasdocumented in presynaptic terminals. However, innervation of diaphragm musclefibers was only slightly increasedin nandrolone-treated SOD1-mutant mice. Altogether the results point out and definefine structural alterations ofdiaphragm NMJs in the murine model of familial ALS at symptom onset, and indicate that nandrolone may preventor delay structural alterations in NMJ mitochondria and stimulate presynaptic activity but does not prevent muscledenervation during the disease