Figure 1.
ZIP impairs ORM reconsolidation but does not affect ORM consolidation. A, Rats were trained in NOR using two different objects (A and B, day 1, TR) and 24 h later (day 2) submitted to an ORM RA session in the presence of familiar object A and novel object C. Immediately after RA, rats received intra-CA1 infusions of VEH (saline), ZIP, or Src-ZIP. One day later (day 3, TEST), rats were exposed to a familiar object (A, B, or C) and novel object (D) to evaluate retention. Data (mean ± SEM) are presented as DI during TR, RA, and TEST, n = 9–10 per group. Rats explored objects equally during TR (A = 28.81 ± 1.14 s, B = 30.6 ± 1.13 s, t(83) = 1.548, p = 0.125) and discriminated them during RA (A = 21.29 ± 0.961 s, C = 35.74 ± 1.285 s, t(83) = 19.10, p < 0.001). Total object exploration time did not differ among TR, RA, and TEST (F(2,249) = 1.257, p = 0.286). B, Rats were treated as in A, but received intra-CA1 VEH or ZIP 6 h (left) or 12 h (right) after RA. Data (mean ± SEM) are presented as DI during TR, RA, and TEST, n = 8–10 per group. Rats explored objects equally during TR (left: A = 27.12 ± 1.68 s, B = 28.85 ± 1.51 s, t(51) = 1.111, p = 0.2717; right: A = 31.87 ± 1.242 s, B = 33.31 ± 1.31 s, t(57) = 0.967, p = 0.338) and discriminated them during RA (left: A = 21.84 ± 1.26 s, C = 38.02 ± 1.76 s, t(51) = 12.61, p < 0.001; right: A = 25.60 ± 0.95 s, C = 40.93 ± 1.38 s, t(57) = 16.33, p < 0.001). Total object exploration time did not differ among TR, RA, and TEST (left: F(2,153) = 2.357, p = 0.0981; right: F(2,171) = 2.885, p = 0.0586). C, Rats were treated as in A, but RA was performed 7 d after TR (left) or TEST was performed 7 d after RA (right). Data (mean ± SEM) are presented as DI during TR, RA, and TEST, n = 9–10 per group. Rats explored objects equally during TR (left: A = 24.94 ± 1.24 s, B = 26.86 ± 1.08 s, t(57) = 1.60, p = 0.115; right: A = 27.48 ± 1.07 s, B = 28.09 ± 1.12 s, t(57) = 0.484, p = 0.63) and discriminated them during RA (left: A = 19.31 ± 0.71 s, C = 31.14 ± 1.06 s, t(57) = 16.85, p < 0.001; right: A = 21.0 ± 0.77 s, C = 35.23 ± 1.16 s, t(57) = 16.96, p < 0.001). Total object exploration time did not differ among TR, RA, and TEST (left: F(2,171) = 2.33, p = 0.101; right: F(2,171) = 2.71, p = 0.067). D, Rats were treated as in A, but RA was performed in the presence of familiar objects A and B. Data (mean ± SEM) are presented as DI during TR, RA, and TEST, n = 10 per group. Rats explored objects equally during TR (A = 26.89 ± 1.88 s, B = 29.39 ± 1.71 s, t(19) = 1.35, p = 0.193) and did not discriminate them during RA (A = 23.11 ± 1.7 s, C = 24.52 ± 1.70 s, t(19) = 0.95, p = 0.354). Total object exploration time did not differ among TR, RA, and TEST (F(2,57) = 1.95, p = 0.152). E, Rats were treated as in A, but 24 h after TR, they explored the training arena in the absence of objects. Data (mean ± SEM) are presented as DI during TR and TEST, n = 8–9 per group. Rats explored objects equally during TR (A = 27.87 ± 1.30 s, B = 29.37 ± 1.17 s, t(50) = 1.149, p = 0.256). Total object exploration time did not differ between TR and TEST (t(100) = 1.252, p = 0.214). F, Rats were treated as in A, but 24 h after TR, they explored two novel objects (C and D; TR2). Data (mean ± SEM) are presented as DI during TR, TR2, and TEST, n = 8–10 per group. Rats explored objects equally during TR (A = 31.25 ± 1.36 s, B = 31.34 ± 1.43 s, t(70) = 0.0596, p = 0.953) and TR2 (C = 32.14 ± 1.56 s, D = 30.54 ± 1.52 s, t(70) = 0.935, p = 0.353). Total object exploration time did not differ among TR, TR2, and TEST (F(2,210) = 1.55, p = 0.215). G, Rats were treated as in A, but ORM was evaluated 3 h after RA. Data (mean ± SEM) are presented as DI during TR, RA, and TEST, n = 9–10 per group. Rats explored objects equally during TR (A = 36.65 ± 3.06 s, B = 34.98 ± 2.05 s, t(18) = 0.530, p = 0.602) and discriminated them during RA (A = 25.7 ± 2.00 s, C = 42.88 ± 2.47 s, t(18) = 10.07, p < 0.001). Total object exploration time did not differ among TR, RA, and TEST (F(2,54) = 0.115, p = 0.892). H, Rats were treated as in A, but 15 min before RA, received intra-CA1 infusions of VEH or MUS and, immediately after RA, were given VEH or ZIP in the dorsal CA1. Data (mean ± SEM) are presented as DI during TR, RA, and TEST, n = 12 per group. Rats explored objects equally during TR (A = 22.55 ± 0.81 s, B = 22.21 ± 0.73 s, t(47) = 0.402, p = 0.67). Rats that received VEH before RA (A = 15.47 ± 0.87 s, C = 28.57 ± 1.39 s, t(23) = 7.65, p < 0.001), but not those given MUS (A = 21.88 ± 1.71 s, C = 18.55 ± 1.46, t(47) = 1.62, p = 0.119), discriminated objects during RA. Total object exploration time did not differ among TR, RA, and TEST (F(2,141) = 1.69, p = 0.188). I, Rats were trained as in A and, 24 h later, submitted to RA in the presence of familiar object A and novel object C. At different times after RA, rats were killed and the CA1 region of the dorsal hippocampus was dissected out and homogenized to determine PKMζ levels by immunoblot. PKMζ levels were also evaluated 360 min after ORM RA in the presence of familiar objects A and B (AB360). Data are expressed as mean ± SEM, n = 4. TUB, β-tubulin. J, Rats were trained as in A and immediately (0 h; left), 24 h (center), or 168 h (right) after TR received intra-CA1 infusions of VEH or ZIP. ORM retention was evaluated 24 h later. Data (mean ± SEM) are presented as DI during TR and TEST, n = 10–11 per group. Rats explored objects equally during TR (left: A = 22.86 ± 1.61 s, B = 25.78 ± 2.84 s, t(19) = 1.257, p = 0.224; center: A = 30.7 ± 1.97 s, B = 29.08 ± 1.8 s, t(19) = 0.84, p = 0.412; right: A = 25.78 ± 1.29 s, B = 27.39 ± 1.15 s, t(21) = 1.265, p = 0.22). Total object exploration time did not differ between TR and TEST (left: t(38) = 0.646, p = 0.523; center: t(38) = 1.47, p = 0.149; right: t(42) = 1.82, p = 0.076). In all graphs, dashed lines represent chance level; #p < 0.05 in one-sample Student's t test with theoretical mean = 0; *p < 0.05, **p < 0.01, and ***p < 0.001 in unpaired t test or Bonferroni's multiple-comparisons test after one-way or two-way ANOVA.