Figure 5.
PKMζ inhibition erases the reactivated recognition trace. A, Rats were trained in NOR using two different stimuli objects (A and B, day 1, TR) and immediately thereafter received bilateral infusions of VEH (saline) or ANI into the EC. One day later (day 2, TEST), rats were exposed to familiar object A and novel object D for 5 min to evaluate ORM retention. Data (mean ± SEM) are presented as DI during TR and TEST, n = 12 per group. Rats explored objects equally during TR (A = 28.7 ± 2.83 s, B = 29.79 ± 3.05 s, t(23) = 0.480, p = 0.635). Total object exploration time did not differ between TR and TEST (t(46) = 0.222, p = 0.825). B, Rats were trained as in A and, 24 h after TR (day 2), were submitted to a 5-min-long ORM RA in the presence of two familiar objects (A and B) or in the presence of familiar object A and novel object C. Immediately after RA, rats received bilateral intra-EC infusions of VEH or ANI. One day later (day 3, TEST), rats were exposed to familiar object A and novel object D for 5 min to evaluate ORM retention. Data (mean ± SEM) are presented as DI during TR, RA, and TEST, n = 11 per group. Rats explored objects equally during TR (left: A = 24.57 ± 2.56 s, B = 23.54 ± 1.81 s, t(21) = 0.371, p = 0.714; right: A = 24.07 ± 2.59 s, B = 23.37 ± 2.71 s, t(21) = 0.432, p = 0.670). Rats submitted to RA in the presence of familiar objects (AB) did not discriminate between them during that session (A = 21.90 ± 0.66 s, B = 20.05 ± 1.27 s, t(21) = 1.50, p = 0.148). Rats submitted to RA in the presence of familiar object A and novel object C discriminated the objects during that session (A = 21.77 ± 2.34 s, B = 32.87 ± 2.75 s, t(21) = 5.47, p < 0.001). Total object exploration time did not differ among TR, RA, and TEST (left: F(2,63) = 1.81, p = 0.172; right: F(2,63) = 0.721, p = 0.490). C, Rats were trained as in A and, 24 h after TR (day 2), were submitted to a 5-min-long ORM RA in the presence of familiar object A and novel object C. Immediately after RA, rats received bilateral intra-CA1 infusions of VEH or ZIP. One day later (day 3, TEST 1), rats were exposed to familiar object A and novel object D for 5 extra minutes to evaluate ORM retention and, immediately thereafter, received bilateral infusions of VEH or ANI in the EC. One day later (day 4, TEST 2), rats were exposed to familiar object A and novel object E for 5 min to evaluate ORM retention. Data (mean ± SEM) are presented as DI during TR, RA, TEST1, and TEST2, n = 9 per group. Rats explored objects equally during TR (A = 25.77 ± 1.16 s, B = 29.59 ± 1.88 s, t(35) = 1.98, p = 0.055) and discriminated them during RA (A = 20.66 ± 1.30 s, B = 34.59 ± 1.79 s, t(35) = 10.42, p < 0.001). Total object exploration time did not differ between TR, RA, TEST1, and TEST2 (F(3,140) = 0.105, p = 0.957). In all graphs, dashed lines represent chance level; #p < 0.05 in one-sample Student's t test with theoretical mean = 0; ***p < 0.001 in unpaired t test or Bonferroni's multiple-comparisons test after two-way ANOVA.