Figure 3.

Effects of L-type Ca²⁺ channel peptide on voltage-dependent enhancement of neurotransmitter release. (a) mEPSPs induced by 0.5 M sucrose (Left) or 0.5 M sucrose plus a presynaptic tetanic stimulation at 100 Hz for 4 s (Right). As a control, 140 μM L_II-III(670–800) of α_1S from the skeletal muscle L-type Ca²⁺ channel was injected in Krebs solution containing 0 mM Ca²⁺ and 10 mM Mg²⁺. mEPSPs from one representative experiment recorded 5 and 4 min before injection and 15, 16, 25, and 26 min after injection are illustrated. (b) Difference between normalized average integral values of the mEPSPs with and without presynaptic action potentials is plotted from seven experiments like the one illustrated in a.