Figure 4.

The effect of SR-95531 on eIPSCs at low release probability. A, IPSC were evoked with a reduced (0.5 mm) concentration of Ca²⁺ in control (left) and in the presence of 100 μm SR-95531 (right). B, In these conditions, the failure rate was typically ∼60% and was not affected by application 100 μm SR-95531 (black and gray bars). The amplitude of the evoked events was reduced by the same amount as in control conditions (white bar). Lowering Ca²⁺ decreased the rise time of evoked events (E, white and black bars). Application of 100 μm SR-95531 in conditions of lowered release probability increased the rise time of individual events, as shown by the cumulative distribution in C. This effect was significant across cells (pooled distribution of rise times in D and individual and average values in E, black and gray bars; n = 10). F, G, Continuous recording of quantal events before (F) and after (G) application of 100 μm SR-95531 (individual sweeps and their average are shown on the right of each trace). The rise time of individual events is prolonged by the antagonist, as shown for one cell in H. Cum. Prob., Cumulative probability. The pooled distributions in seven cells and their individual and average values of rise time are reported in I and J, respectively. Error bars indicate SDM.