title: Effects of physiologic alterations on binomial transmitter release at magnesium-depressed neuromuscular junctions.
abstract: 1. Transmitter release from Mg2+-treated frog neuromuscular junctions can be described by binomial statistics. Good agreement between the observed amplitude-frequency distribution of e.p.p.s. and that predicted by binomial statistics is observed with relatively low concentrations of Mg2+. Conversely, good agreement is found with Poisson predictions when higher concentrations of Mg2+ are used to depress transmission. 2. Binomial analysis at these junctions shows that Mg2+ reduces quantal content (m), the probability of release (p) and to a lesser extent the available stores of transmitter (n). Raising Ca2+ causes an increase in n and p and a small but significant increase in n. K+ increases m and p but not n. 3. During 'frequency-facilitation' (1-6 Hz), e.p.p.s., m and n are increased but p is unaffected. 4. It is concluded that binomial statistics can be used to estimate the quantal parameters of transmitter release and that these parameters can be identified as discrete entities.
mesh_terms: D000818:Animals; D001001:Anura; D002118:Calcium / Q000494:pharmacology; D004558:Electric Stimulation; D004594:Electrophysiology; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology*; D009045:Motor Endplate / Q000502:physiology; D009469:Neuromuscular Junction / Q000187:drug effects / Q000502:physiology*; D009489:Neurosecretion / Q000187:drug effects; D011188:Potassium / Q000494:pharmacology; D011894:Rana pipiens; D013223:Statistics as Topic; D009435:Synaptic Transmission / Q000187:drug effects
chemical_list: D008274:Magnesium; D011188:Potassium; D002118:Calcium