Novelty exposure overcomes foot shock-induced spatial-memory impairment by processes of synaptic-tagging in rats.
Novelty processing can transform short-term into long-term memory. We propose that this memory-reinforcing effect of novelty could be explained by mechanisms outlined in the "synaptic tagging hypothesis." Initial short-term memory is sustained by a transient plasticity change at activated synapses and sets synaptic tags. These tags are later able to capture and process the plasticity-related proteins (PRPs), which are required to transform a short-term synaptic change into a long-term one. Novelty is involved in inducing the synthesis of PRPs [Moncada D, et al. (2011) Proc Natl Acad Sci USA 108:12937-12936], which are then captured by the tagged synapses, consolidating memory. In contrast to novelty, stress can impair learning, memory, and synaptic plasticity. Here, we address questions as to whether novelty-induced PRPs are able to prevent the loss of memory caused by stress and if the latter would not interact with the tag-setting process. We used water-maze (WM) training as a spatial learning paradigm to test our hypothesis. Stress was induced by a strong foot shock (FS; 5 × 1 mA, 2 s) applied 5 min after WM training. Our data show that FS reduced long-term but not short-term memory in the WM paradigm. This negative effect on memory consolidation was time- and training-dependent. Interestingly, novelty exposure prevented the stress-induced memory loss of the spatial task and increased BDNF and Arc expression. This rescuing effect was blocked by anisomycin, suggesting that WM-tagged synapses were not reset by FS and were thus able to capture the novelty-induced PRPs, re-establishing FS-impaired long-term memory.
Departamento de Neurofisiología Experimental, Centro Internacional de Restauración Neurológica, Havana 11300, Cuba.
William
W
Almaguer-Melian
Jorge
J
Bergado-Rosado
Nancy
N
Pavón-Fuentes
Esteban
E
Alberti-Amador
Daymara
D
Mercerón-Martínez
Julietta U
JU
Frey
D000818:Animals; D004597:Electroshock; D005106:Exploratory Behavior; D005528:Foot / Q000473:pathology*; D005786:Gene Expression Regulation; D008297:Male; D018782:Maze Learning; D008568:Memory / Q000502:physiology*; D008569:Memory Disorders / Q000503:physiopathology*; D014176:Protein Biosynthesis; D051381:Rats; D017208:Rats, Wistar; D013569:Synapses / Q000378:metabolism*; D013997:Time Factors