Intrahippocampal infusion of adenosine immediately after nonreinforced retrieval hindered recent and late spatial memory retention, as measured 24 h and 5 d after infusion. Male Wistar rats with infusion cannulas implanted into the CA1 region of the dorsal hippocampus were trained for 5 d in the spatial version of the MWM. Twenty-four hours after the last training session, the animals were randomly assigned to one out of five experimental groups and subjected to a 60-sec probe test in the absence of the escape platform. Immediately after this first test, the animals received intrahippocampal bilateral infusions (black arrow) of either saline solution (saline) or adenosine (A 0.1, 1, 10, or 100 nmol). Memory retention was assessed in successive 60-sec probe tests carried out either 24 h or 5 d after the first test. Data are expressed as means (±SD) of the percentage of swimming time spent in the target quadrant. (Dots) Individual value for each rat, (dashed line) theoretical mean of 25% of test time spent in the target quadrant at random. (*) P < 0.05, (**) P < 0.01 versus respective saline groups; one-way ANOVA: test 24 h after the first test, F(4,48) = 5.933; test 5 d after the first test, F(4,48) = 3.321; Dunnett's posttest; n = 7–12 per group.
