Novelty enhances retrieval: molecular mechanisms involved in rat hippocampus.
Rats exposed to a novel environment just prior to or 1-2 h, but not 4 or 6 h, before retention testing exhibited an enhanced retrieval of a one-trial inhibitory avoidance training. The bilateral intrahippocampal infusion of PD098059, an inhibitor of mitogen-activated protein kinase (MAPK), the specific upstream activator of p42 and p44 MAPKs, given 10 min before the exposure to the novel environment, blocked the enhancing effect of novelty on memory retrieval. In addition, prenovelty infusion of DL-2-amino-5-phosphonovalerate (APV), an antagonist of glutamate NMDA receptors, produced similar effects. The exposure to the novel environment is associated with an activation of p42 and p44 MAPKs and an increase in the phosphorylation state of the transcription factor cAMP response element binding protein (CREB). No changes were observed in cAMP-dependent protein kinase (PKA) activity or in alpha-CAMKII activation. Taken together, our results indicate that novelty activates hippocampal MAPKs, which are necessary, along with glutamate NMDA receptors, for the enhancing effect of novelty on retrieval.
Izquierdo
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LA
Centro de Memoria, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Ramiro Barcellos 2600 (90035-003) Porto Alegre, RS, Brazil.
Viola
H
H
Barros
D M
DM
Alonso
M
M
Vianna
M R
MR
Furman
M
M
Levi de Stein
M
M
Szapiro
G
G
Rodrigues
C
C
Choi
H
H
Medina
J H
JH
Izquierdo
I
I
D000818:Animals; D001362:Avoidance Learning / Q000502:physiology; D005106:Exploratory Behavior / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology / Q000502:physiology*; D017774:Long-Term Potentiation / Q000502:physiology*; D008297:Male; D008568:Memory / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009474:Neurons / Q000201:enzymology; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism
D016194:Receptors, N-Methyl-D-Aspartate; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases