Substance P release from K+-depolarized rat brain synaptosomes at one-second resolution

Substance P release from isolated nerve endings (synaptosomes) prepared from rat brain occurred primarily within the first second of continuous K+-depolarization. If the concentrations of K+ or Ca2+ were decreased there was less substance P release, but the time course of release was similar. Thus the rapid release of substance P occurs over a wide range of depolarization conditions.