On the participation of adenosinergic receptors in the reconsolidation of spatial long-term memory in male rats

(A) Intrahippocampal infusion of adenosine after the final day of training does not affect early 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 received intrahippocampal bilateral infusions of either saline solution (saline) or 10 nmol of adenosine (A 10 nmol). Memory retention was assessed in successive 60-sec probe tests carried out either 24 h or 5 d after infusion (INF; black arrow). (Dots) Individual value for each rat, (dashed line) theoretical mean of 25% of test time spent at random in the target quadrant. Data are expressed as means (±SD) of the percentage of swimming time spent in the target quadrant. There was no difference between the saline and adenosine groups; Student's t-test: test 24 h after the first test, t₍₁₉₎ = 2.065; test 5 d after the first test, t₍₁₉₎ = 1.397; n = 10–11 per group. (B) Intrahippocampal infusion of adenosine immediately after reinforced retrieval does not affect early and late spatial memory retention, as measured 24 h and 5 d after the first test. 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 subjected to a 60-sec probe test in the presence of the escape platform (R). Immediately after R, the animals received intrahippocampal bilateral infusions (black arrow) of either saline solution (saline) or 10 nmol of adenosine (A 10 nmol). Memory retention was assessed in successive 60-sec probe tests carried out either 24 h or 5 d after R. (Dots) Individual value for each rat, (dashed line) theoretical mean of 25% of test time spent at random in the target quadrant. Data are expressed as means (±SD) of the percentage of swimming time spent in the target quadrant. There was no difference between the saline and adenosine groups; Student's t-test: test 24 h after the first test, t₍₁₆₎ = 0.3869; test 5 d after the first test, t₍₁₆₎ = 0.4349; n = 6–12 per group. (C) Intrahippocampal infusion of adenosine 3 h after nonreinforced retrieval does not affect early and late spatial memory retention, as measured 24 h and 5 d after the first test. 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 subjected to a 60-sec probe test in the absence of the escape platform. Three hours after this test, the animals received intrahippocampal bilateral infusions (black arrow) of either saline solution (saline) or 10 nmol of adenosine (A 10 nmol). Memory retention was assessed in successive 60-sec probe tests carried out either 24 h or 5 d after the first test. (Dots) Individual value for each rat, (dashed line) theoretical mean of 25% of test time spent at random in the target quadrant. Data are expressed as means (±SD) of the percentage of swimming time spent in the target quadrant. There was no difference between the saline and adenosine groups; Student's t-test: test 24 h after the first test, t₍₁₂₎ = 1.923; test 5 d after the first test, t₍₁₂₎ = 0.6724; n = 6–8 per group. (D) Intramediolateral occipital cortex infusion of adenosine immediately after nonreinforced retrieval does not affect early and late spatial memory retention, as measured 24 h and 5 d after the first test. Male Wistar rats with infusion cannulas implanted into the mediolateral occipital cortex were trained for 5 d in the spatial version of the MWM. Twenty-four hours after the last training session, the animals were subjected to a 60-sec probe test in the absence of the escape platform. Immediately after this test, the animals received intramediolateral occipital cortex bilateral infusions (black arrow) of either saline solution (saline) or 10 nmol of adenosine (A 10 nmol). Memory retention was assessed in successive 60-sec probe tests carried out either 24 h or 5 d after the first test. (Dots) Individual value for each rat, (dashed line) theoretical mean of 25% of test time spent at random in the target quadrant. Data are expressed as means (±SD) of the percentage of swimming time spent in the target quadrant. There was no difference between the saline and adenosine groups; Student's t-test: test 24 h after the first test, t₍₁₁₎ = 2.170; test 5 d after the first test, t₍₁₁₎ = 0.6221; n = 6–7 per group.