Figure 1.

Voltage-dependent enhancement of neurotransmitter release. mEPSPs in Krebs solution containing 0 mM Ca²⁺ and 10 mM Mg²⁺ induced by a puff-application of 0.5 M sucrose for 2 s onto synaptic pairs of sympathetic neurons in culture, at 5 min before injection (a) and 9 min (b) and 19 min (c) after disruption of the membrane patch for injection of BAPTA from a suction pipette containing 20 mM BAPTA. mEPSPs triggered by 0.5 M sucrose were facilitated by simultaneously applied presynaptic current pulses (4 nA) for 5 ms at 100 Hz for 4 s (a–c vs. d–f). mEPSPs 4 min before injection (d), and 10 min (e) and 20 min (f) after BAPTA injection are shown. (a–f) mEPSPs from one representative experiment are illustrated. The large deflection before the application of sucrose in a is an action potential. (g) Normalized average integral values of mEPSPs with (□) or without (■) presynaptic action potentials induced by 400 pulses at 100 Hz are plotted from six experiments like the one illustrated in a–f.