D1/D5 agonist-dependent inhibition of depotentiation depends on the timing of agonist application. Columns represent mean ± SEM for the drug–control differences of the normalized fEPSP slopes in each slice (percentage). Theupward direction of columns means an inhibition of depotentiation by the drug. A, Inhibition of depotentiation was strong when agonist (6-Chloro-PB, 10 μm) was applied starting 5 min before the tetanus and left until the end of LFS (3 Hz/3 min). B, When D1/D5 agonist was applied only before and during the induction of LTP, but was absent during LFS, depotentiation was not affected.C, Depotentiation was strongly inhibited by D1/D5 agonist applied after the tetanus and during LFS. The time of drug application is marked by the horizontal bar; the moment of tetanus is indicated by the upward arrow; LFS is shown by a small downward arrow. Levels of significance in the post hoc paired t test: °p < 0.1; *p < 0.05; **p < 0.01; ***p < 0.001.F, p, and n values for two-way ANOVA are listed in Results.