Prevention by ritanserin (RIT) 10 mg kg−1 i.p., given 30 min before EEDQ, of the impairing effect of EEDQ (10 mg kg−1 s.c.), given 48 h before the acquisition session, on passive avoidance retention in rats. Values are mean±s.e.mean of 10–12 animals. *P<0.05, **P<0.01 vs control; †P<0.05, ††P<0.01 vs EEDQ or 8-OH-DPAT; #P<0.05 vs EEDQ+8-OH-DPAT (one-way ANOVA, F6,68=9.4, followed by Student-Newman-Keul's test).