The amnesic effect induced by the intrahippocampal infusion of adenosine is blocked by A1 and A3 but not by A2A or A2B receptor antagonists. 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 final training session, the animals were 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), 10 nmol of adenosine (A 10 nmol), or 10 nmol of adenosine plus A1 (A + antag A1), A2A (A + antag A2A), A2B (A + antag A2B), or A3 (A + antag A3) receptor antagonist (50 nmol for each antagonist). 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(5,71) = 4.733; test 5 d after the first test, F(5,71) = 3.895; Dunnett's posttest; n = 9–18 per group.
