Figure 3

Actions of isoflurane (ISO, 1 MAC), low extracellular Ca²⁺ (0.8 – 1.0 mM), TTX (60 nM), CNQX (10 μM) and 50% stimulus (STIM) voltage. Experiments with 0.8 mM and 1.0 mM external Ca²⁺ were pooled, as the changes in facilitation and EPSP depression under each condition were almost identical. The actions of these treatments are shown for EPSP depression (top panel), FV-EPSP curve slopes (I/O slopes; middle panel) and paired-pulse facilitation (PPF; lower panel). Each bar represents the mean ± standard deviation for at least five experiments from different slice preparations. Note that each treatment substantially depressed EPSPs but only isoflurane and low Ca²⁺ produced a significant change in the I/O slope compared to TTX (p < 0.001 in both cases, ANOVA). PPF with isoflurane and low Ca²⁺ was also significantly greater than with TTX (p < 0.001 and p < 0.001 respectively, ANOVA).