Behavioural neuroscienceMemory consolidation induces N-methyl-d-aspartic acid-receptor- and Ca2+/calmodulin-dependent protein kinase II-dependent modifications in α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor properties
Section snippets
Inhibitory avoidance training
Male Wistar rats (3-month-old, 250–280g) were trained in a IA paradigm, a hippocampal-dependent learning task in which stepping-down from a platform present in a given context is associated with a footshock resulting in an increase in step-down latency (Bernabeu et al 1997, Bevilaqua et al 2003; Cammarota et al., 2004). The IA training apparatus consists of a 50×25×25cm Plexiglas box with a 5cm high, 8cm-wide and 25cm long platform on the left end of a series of bronze bars that make the floor
Results
To investigate whether consolidation of IA memory requires functional NMDAr and CaMKII in the hippocampus, male Wistar rats were trained in IA and, immediately after training, received bilateral infusions of vehicle (saline), the NMDAr antagonist AP5 (25nmol/side) or the CaMKII inhibitor KN-93 (10nmol/side) into the CA1 region of the dorsal hippocampus. Memory retention was evaluated in a non-reinforced test session carried out 24 h later (TT1). AP5 and KN-93 significantly reduced test
Discussion
Our experiments show that the intra-CA1 infusion of AP5 and KN-93 immediately after training hindered retention of IA long-term memory as assessed 24 and 72 h after training (Fig. 1; TT1 and TT2, respectively). We also found that, when submitted to a second training session, those same animals normally acquired the avoidance response and did so as if they had never been trained before (Fig. 1; TT3). These results strongly suggest that inhibition of NMDAr and CaMKII in the CA1 region of the
Conclusion
In conclusion, our results show the necessity of hippocampal NMDAr and CaMKII for the consolidation of IA memory and suggest the existence of a memory-relevant, CaMKII-mediated link between the activation of hippocampal NMDAr and learning-induced modifications of AMPAr properties.
Acknowledgments
This work was supported by grants from ANPCyT and CONICET, Argentine and CNPq, and CAPES, Brazil.
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