Both augmentation and potentiation occur independently of internal Ca2+ at the frog neuromuscular junction.
Augmentation and potentiation of surface recorded endplate potentials (EPPs) were examined during and after tetanic nerve stimulation in both the normal and BAPTA (a Ca2+-chelator)-loaded frog neuromuscular junction (NMJ). In the BAPTA-loaded NMJ, in contrast to a great reduction of facilitation, the amplitudes and the time constants of augmentation and potentiation were almost the same as those in the normal NMJ. The slowly increasing process of transmitter release during tetanus was a little larger in the BAPTA-loaded NMJ than in the normal NMJ. These observations strongly suggest that both augmentation and potentiation occur independently of internal Ca2+ concentration.
Tanabe
N
N
Department of Biology, Daiichi College of Pharmaceutical Sciences, Fukuoka, Japan.
Kijima
H
H
D000200:Action Potentials; D000818:Animals; D002118:Calcium / Q000502:physiology*; D004533:Egtazic Acid / Q000494:pharmacology / Q000031:analogs & derivatives; D004558:Electric Stimulation; D066298:In Vitro Techniques; D009045:Motor Endplate / Q000502:physiology; D009469:Neuromuscular Junction / Q000502:physiology*; D011898:Ranidae / Q000502:physiology*
D004533:Egtazic Acid; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium