Excitatory Neuromuscular transmission in crayfish: calcium dependence is unaffected by picrotoxin

Picrotoxin, 1 X 10(-5)M to 1.6 X 10(-3)M, had little or no effect on the amplitude of intracellularly recorded excitatory junctional potentials (EJPs) at extracellular calcium concentrations [Ca2+]0 ranging from 0.5 to 15 mM. The slope of the log EJP vs. log[Ca2+]0 relationship was approximately 1 with or without picrotoxin. The reduction EJP amplitude resulting from the addition of 5 X 10(-5)M GABA was largely reversed by 10(-5)M picrotoxin.