Fig. 4.

Inhibition of neurotransmitter release by forskolin and 8-Br-cAMP. a Effect of PKA inhibition on noradrenaline release measured in the presence of 8-Br-cAMP. Shown is a superfusion experiment with 8-Br-cAMP (100 μM) alone (filled triangles) or 8-Br-cAMP together with H89 (1 μM, open circles; six determinations ± SEM). Collected radioactivity is expressed as percent of the total amount taken up by the cells. b Mean S2/S1 ratios of the depolarisation-induced noradrenaline release when forskolin (Fsk, 10 μM) or 8-Br-cAMP (cAMP, 100 μM) were added beginning 20 min before S2. The effect of 8-Br-cAMP was assessed in the presence of the Src-family kinase inhibitor PP1 (1 μM, cross-hatched bar). Error bars represent 99 % confidence intervals, n ≥12. The horizontal line shows the mean S2/S1 ratio in controls; the dotted area represents the lower 99 % confidence interval taken from Fig. 2b. Release reduction by forskolin and 8-Br-cAMP was statistically significant relative to controls (Kruskal–Wallis one-way ANOVA followed by Dunn’s test). Asterisk indicates that the effect of PP1 on release inhibition by 8-Br-cAMP was significant (relative to 8-Br-cAMP and forskolin)