The Effect of Resistance Training and Androgen Administration on Neuromuscular Junction Morphology and Neurotrophin Expression.

Abstract

This study examined the effect of resistance training (RT) and nandrolone decanoate (ND) administration on neuromuscular junction (NMJ) morphology and neurotrophin expression. Forty 3-month-old male C57Bl/6J mice were randomized to an RT or sedentary (SED) group. Each group of animals was further divided into sham (S) or ND (35 mg·kg -1 ·wk -1 ) groups. All interventions were 7 wk in duration. Brain-derived neurotrophic factor (BDNF), tropomyosin receptor kinase B (TrkB), p75, and androgen receptor (AR) expression in the plantaris and soleus muscles were examined via Western blot, whereas NMJ morphology was examined via immunofluorescence. Significant interactions for BDNF expression were noted in the plantaris ( P = 0.009) and soleus ( P = 0.010). In the plantaris BDNF expression for RT-ND was greater than RT-S ( P = 0.019) and SED-ND ( P = 0.016), whereas BDNF expression in RT-S was greater than all other groups ( P 's < 0.05) in the soleus. A significant interaction for TrkB expression was observed in the plantaris. TrkB in RT-ND was significantly greater ( P = 0.031) than SED-ND. Analysis of the postsynaptic membrane within the plantaris revealed that RT increased the acetylcholine (ACh) receptor-stained area ( P = 0.036), ACh-stained perimeter ( P = 0.006), and total area ( P = 0.044) compared with SED. In addition, ND administration increased ( P = 0.050) ACh total area. In the presynaptic membrane, both RT and ND increased ACh vesicle-stained area ( P < 0.001 and P = 0.006, respectively), ACh vesicle-stained perimeter ( P < 0.001 and P = 0.02, respectively), and ACh vesicle total area ( P < 0.001 and P = 0.01, respectively), whereas RT only was noted to increase presynaptic ACh vesicles total perimeter ( P < 0.001). In the soleus, ND increased ACh receptor-stained ( P = 0.002) and total area ( P = 0.035) at the post-synaptic membrane. RT and ND administrations stimulate increases in neurotrophin expression and NMJ morphology in plantaris and soleus muscles.