Fig. 5. Effect of increased inhibition on Ca entry and the excitatory junction potentials (EJPs). (A) More inhibitor stimuli caused slightly greater inhibition of Ca entry (excitor black, inhibitor grey). With the inhibitor stimulated in the standard manner (left-hand traces; eight inhibitor stimuli at 100 Hz), inhibition was 13±2% (mean ± S.E.M.), and with more inhibitor stimuli (right-hand traces, 24 stimuli at 100 Hz) inhibition was slightly greater: 22±2% (paired t-test, P<0.05, N=14 terminals from two preparations). Fluorescence transients measured from the excitor terminals, using Calcium Green-1, are depicted next to the terminals (arrows). Black traces resulted from stimulating the excitor alone, while grey traces resulted from stimulating the excitor and inhibitor together. The action potential was conducted from the bottom right to the top left. Scale bars indicate 5% F/F (vertical) and 50 µm (horizontal). (B) Increased stimulation of the inhibitor axon resulted in greater inhibition (10%) of the second and third EJP (paired t-test, P<0.05, N=10 cells from three preparations). Black bars represent eight inhibitor stimuli, while grey bars represent 24 inhibitor stimuli.