The importance of phospholipase A2 in the early induction by crotoxin of biphasic changes in endplate potentials at the frog neuromuscular junction.
In Ca2+-Ringer, crotoxin induced a rapid fall in amplitude of endplate potentials followed by a marked secondary rise but, in Ca2+-free, Sr2+-EGTA Ringer, crotoxin failed to elicit either response. In Ca2+-washout experiments, the onset of giant miniature endplate potentials indicated that binding of crotoxin occurred in Sr2+-EGTA Ringer. Facilitation of endplate potential amplitude due to a closely spaced twin impulse was increased to 162% of control near the peak of the crotoxin-induced secondary phase. These findings are consistent with the phospholipase A2 subunit acting specifically at the active zone.
Hawgood
B J
BJ
Department of Physiology, King's College London, U.K.
Smith
I C
IC
D000818:Animals; D002118:Calcium / Q000502:physiology; D003435:Crotalid Venoms / Q000494:pharmacology*; D003439:Crotoxin / Q000494:pharmacology*; D004533:Egtazic Acid / Q000494:pharmacology; D004790:Enzyme Induction / Q000187:drug effects; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009045:Motor Endplate / Q000187:drug effects*; D009469:Neuromuscular Junction / Q000187:drug effects*; D010740:Phospholipases / Q000096:biosynthesis*; D010741:Phospholipases A / Q000096:biosynthesis*; D054467:Phospholipases A2; D011894:Rana pipiens
D003435:Crotalid Venoms; D004533:Egtazic Acid; D003439:Crotoxin; D010740:Phospholipases; D010741:Phospholipases A; D054467:Phospholipases A2; D002118:Calcium