Factors causing different properties at neuromuscular junctions in fast and slow rat skeletal muscles

摘要: Neuromuscular junctions on fast and slow skeletal muscle fibers have different properties. Possible reasons for these differences were examined in adult rat soleus (SOL) reinnervated at new ectopic or old denervated sites by fibular (FIB) SOL motoneurons. FIB motoneurons formed large with a high density of nerve terminal varicosities (fast appearance), whereas small low (slow appearance). Both appearance when reinnervating endplates. nerves innervating had the same whether they contacted alone (single innervation) together (dual innervation). Continuous stimulation 10 Hz 3–4 months reduced size intact extensor digitorum longus (EDL) caused modest reduction EDL. Junction fiber diameter positively correlated, but slope describing this relation was steeper than junctions. It is concluded that present system (1) motoneuron type not determines character neuromuscular junction, (2) endplates one place stable severe constraints termination pattern axons another type, (3) EDL undergoes to transformation exposed long-term stimulation, (4) only fibers, also firing spatial preformed influence between junction diameter.