Muscle reinnervation--I. Restoration of transmitter release mechanisms.
Following sciatic nerve crush the restoration of neuromuscular transmission in the extensor digitorum longus muscle of rat proceeds in a well defined manner: (a) as soon as the nerve-muscle contact is reformed, a subthreshold end-plate potential is recorded; no 'non-transmitting stage' is observed; (b) 24 hours later muscle action potentials are induced by nerve stimulation; (c) miniature end-plate potentials are absent or very rare at the newly reinnervated end-plates; their frequency returns to normal in about 4 weeks; (d) the frequency is also very much reduced in 30 mM K+ and hypertonic solutions and recovers slowly, in 4 and 5 weeks, respectively, while black widow spider venom is from the beginning as powerful as in normal neuromuscular junctions; (e) at the early stages of reinnervation the Ca2+-dependent release mechanisms are much stronger than control cases, while the Ca2+-independent mechanisms are weaker and recover in 5 weeks. The gradual reassembly and restoration of neurotransmitter release mechanisms of the extensor digitorum longus nerve terminal indicate the complexity of pre-synaptic ending organization.
D000818:Animals; D001696:Biomechanical Phenomena; D002118:Calcium / Q000502:physiology; D004558:Electric Stimulation; D006982:Hypertonic Solutions / Q000494:pharmacology; D008297:Male; D009132:Muscles / Q000502:physiology*; D009409:Nerve Crush; D009411:Nerve Endings / Q000187:drug effects / Q000502:physiology; D009416:Nerve Regeneration / Q000187:drug effects; D018377:Neurotransmitter Agents / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013111:Spider Venoms / Q000494:pharmacology; D013569:Synapses / Q000502:physiology
D006982:Hypertonic Solutions; D018377:Neurotransmitter Agents; D013111:Spider Venoms; D011188:Potassium; D002118:Calcium