Transmitter release at frog end-plate loaded with a Ca2+-chelator, BAPTA: hypertonicity and erythrosin B augment the release independently of internal Ca2+.
A Ca2+-chelator, bis-(aminophenoxy)ethane-tetraacetic acid (BAPTA) was loaded into the presynaptic nerve terminal of frog end-plate. The BAPTA-loaded preparation showed little facilitation. However, the facilitation reappeared upon addition of an ionophore, X-537A, supporting the view that the loss of facilitation was due to the Ca2+-buffering action of BAPTA. Both hypertonic conditions and erythrosin B increased both the size of end-plate potentials and frequency of miniature end-plate potentials without any recovery of facilitation at the BAPTA-loaded end-plate. This suggested that transmitter release was increased by both conditions with little change in internal Ca2+ concentration.
Tanabe
N
N
Department of Biology, Daiichi College of Pharmaceutical Sciences, Fukuoka, Japan.
Kijima
H
H
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002614:Chelating Agents / Q000494:pharmacology*; D004533:Egtazic Acid / Q000494:pharmacology / Q000031:analogs & derivatives; D004923:Erythrosine / Q000494:pharmacology*; D005452:Fluoresceins / Q000494:pharmacology*; D006982:Hypertonic Solutions; D066298:In Vitro Techniques; D007476:Ionophores / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009045:Motor Endplate / Q000187:drug effects / Q000378:metabolism*; D009469:Neuromuscular Junction / Q000378:metabolism*; D011898:Ranidae
D002614:Chelating Agents; D005452:Fluoresceins; D006982:Hypertonic Solutions; D007476:Ionophores; D004533:Egtazic Acid; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D004923:Erythrosine; D002118:Calcium