Recovery of neuromuscular junction morphology following 16 days of spaceflight

It has previously been established that spaceflight elicits alterations in the morphology of the neuromuscular system that includes expansion of the n euromuscular junction (NMJ) and myofiber atrophy. The purpose of this study was to determine the capacity of the neuromuscular system to recover from spaceflight-induced modifications upon return to normal gravity. Soleus mus cles were obtained from rats participating in the 16-day Neurolab space shu ttle mission at 1 day and 14 days after returning to Earth: solei were also taken at the same time points from ground-based control rats. Cytofluoresc ent techniques, coupled with confocal microscopy, were used to assess NMJ m orphology. Histochemistry, in conjunction with phase contrast microscopy, w as employed to examine myofiber size and type. Results indicate that 1 day after landing both pre- and postsynaptic stained areas of the NMJ were sign ificantly (P less than or equal to 0.05) larger in the spaceflight group th an in controls. Moreover, significant myofiber atrophy was demonstrated in animals subjected to 0 gravity. By 14 days following return to the Earth, h owever, NMJ stained areas and muscle fiber size were no longer different fr om control values at that same interval. These results suggest that the neu romuscular system possesses a robust capacity to recover from spaceflight-i nduced perturbations upon return to normal gravitational influences. (C) 20 01 Wiley-Liss, Inc.