Dual type of facilitation at the neuromuscular junction of the frog.
End-plate potentials were recorded intracellularly at the frog neuromuscular junction. Facilitation produced by conditioning shocks applied to the motor nerve was studied in two different ways: using either low-frequency trains in Mg-blocked preparations or using brief high-frequency trains followed by a test shock of variable latency in D-tubocurarine-blocked preparations. In both cases, two distinctly different types of motor end-plates were observed. The first type showed a low quantum content and a marked facilitation without depression, while the second type showed a high quantum content, a poor facilitation, and a marked depression. The physiological significance of these findings is discussed.
D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D002118:Calcium / Q000494:pharmacology; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects; D008274:Magnesium / Q000494:pharmacology; D009045:Motor Endplate / Q000502:physiology; D009469:Neuromuscular Junction / Q000502:physiology*; D011898:Ranidae; D009435:Synaptic Transmission / Q000187:drug effects; D014403:Tubocurarine / Q000494:pharmacology
D008274:Magnesium; D002118:Calcium; D014403:Tubocurarine