title: A dual effect of calcium ions on neuromuscular facilitation.
abstract: 1. The changes in neuromuscular facilitation produced by varying extracellular calcium and magnesium concentrations have been studied at the frog neuromuscular junction using intracellular recording and automatic averaging of responses.2. When [Ca] was elevated three effects were observed: a large increase in transmitter release by the first impulse; a decrease in facilitation at short intervals between impulses; and a prolongation of the time course of the facilitated release. If the release by the first impulse is kept at constant level, by raising both [Ca] and [Mg], facilitation becomes greater at all impulse intervals.3. The results have been discussed in terms of the hypothesis that the action of calcium is responsible for neuromuscular facilitation.
mesh_terms: D000818:Animals; D001001:Anura; D002118:Calcium / Q000494:pharmacology*; D004594:Electrophysiology; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D009469:Neuromuscular Junction / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects; D013997:Time Factors
chemical_list: D008274:Magnesium; D002118:Calcium