Altered Heterosynaptic Plasticity Impairs Visual Discrimination Learning in Adenosine A1 Receptor Knock-Out Mice

Impaired heterosynaptic plasticity in L2/3 neurons from visual cortex of A1R KO mice. a, A scheme of intracellular tetanization, bursts of depolarization-induced postsynaptic spikes without presynaptic activation. b, EPSP amplitude changes after intracellular tetanization in WT and KO animals plotted against the amplitude of control EPSP before plasticity induction. Blue circle symbols, data from WT mice (N = 22 inputs); blue horizontal bar at y-axis, their average; pink square symbols, data from A1R KO mice (N = 20 inputs); pink horizontal bar at y-axis, their average. WT versus KO: 102 ± 6.8 versus 74.5 ± 5.0%, p = 0.0053 (KS test, D = 0.532). c, Frequency of occurrence of LTP and LTD after intracellular tetanization in neurons from WT and KO mice (χ² test, p = 0.033). See Extended Data Figure 2-1 for details of statistical analyses.

Learning on a difficult but not on a simple visual task is impaired in A1R KO mice. a, c, Percentage of correct responses on consecutive testing days 1–5 of learning to touch one stimulus presented on the screen for food reward (stage 2) and days 1–19 of pairwise discrimination, learning to touch correct stimulus of the two presented (stage 3). Pale lines and dot symbols show data for each WT (a) and KO (c) mouse. Large symbols and thick lines show daily averages with SEM for N = 30 WT (triangles, blue) and N = 18 A1R KO (circles, orange) animals. In a and c, averaged data for both WT and KO groups are shown to facilitate comparison. b, Percentage of correct responses during days 1–6 and days 14–19 of pairwise discrimination learning; averages for WT (blue) and KO (orange) groups, and data for each mouse (connected pale symbols). Learning in KO mice: from 40.3 ± 5.5 to 52.7 ± 4.7%; paired Wilcoxon test: V = 145 p = 0.008; paired t test: t = 3.054, df = 17, p = 0.007; learning in WT mice: from 44.9 ± 4.9 to 75.1 ± 2.4%, p < 0.001; paired Wilcoxon test, V = 437; paired t test: t = 6.23, df = 29. Before learning: no difference between WT and KO (p > 0.1, KS and t tests); after learning: p < 0.001; KS test, D = 0.589; t test, t = −4.26, df = 25.69. d, f, Number of correct (darker color) and incorrect (lighter color) responses with SEM (gray bars) on consecutive testing days of stags 2 and 3 learning in WT (d) and KO (f) groups. Horizontal dashed line shows maximal possible number (30) of correct responses per 1 d. e, Number of correct responses plotted against number of incorrect responses on each day of pairwise discrimination task (stage 3, days 1–19) for WT (blue triangles and line) and KO (orange circles and line) groups. Arrows indicate data from the first (D1) and the last (D19) day of testing for WT and KO groups; lines connect data points from consecutive days. See Extended Data Figure 3-1 for details of statistical analyses.

A1R KO mice show no impairment in motor learning, nor an increased anxiety compared with WT controls. a–c, Data from each animal (horizontal dash symbols), and group averages with SEM are shown. a, Latency to fall from an accelerating rotation drum (rotarod test) in WT and KO mice on days 1 and 2. Latency increased on day 2 in both the WT group (from 31.1 ± 3.4 s to 45.9 ± 4.4 s; N = 30; p < 0.001; Wilcoxon test, V = 440; t test, t = 5.24, df = 29) and the KO group (from 29.5 ± 3.3 s to 48.7 ± 7.2 s; N = 18; Wilcoxon test: V = 165, p < 0.001; t test: t = 3.91, df = 17, p = 0.0011). No difference between WT and KO groups (p > 0.7 for days 1 and 2; KS and t tests). b, Percentage of time spent on the open and closed arms of the elevated plus maze. No difference between the WT and KO groups (open arm: 9.0 ± 2.3% vs 10.1 ± 1.7%, p > 0.1; closed arm: 91.0 ± 2.3% vs 89.9 ± 1.7%, p > 0.1; KS and t tests). c, The percentage of time spent during the open field test in the four virtually defined regions: outer, outer-in, center-out, and center. No difference between WT and KO groups for any of the regions: outer, 78.1 ± 1.06% versus 73.2 ± 3.44%; outer-in, 15.1 ± 0.75% versus 18.2 ± 2.33%; center-out, 4.8 ± 0.33% versus 6.3 ± 0.97%; center, 2.0 ± 0.18% versus 2.3 ± 0.31%; p > 0.1 for all WT versus KO comparisons, KS and t tests. See Extended Data Figure 4-1 for details of statistical analyses.