title: On the participation of hippocampal p38 mitogen-activated protein kinase in extinction and reacquisition of inhibitory avoidance memory.
abstract: Inhibitory avoidance (IA) learning relies on the formation of an association between stepping down from a platform present in a certain context (conditioned stimulus; CS) with an aversive unconditioned stimulus (US; i.e. a footshock). A single CS-US pairing establishes a robust long-term memory expressed as an increase in step-down latency at testing. However, repeated retrieval of the avoidance response in the absence of the US induces extinction of IA memory. That is, recurring presentation of the CS alone results in a new learning indicating that the CS no longer predicts the US. Although the signaling pathways involved in the consolidation of IA and other fear-motivated memories have been profusely studied, little is known about the molecular requirements of fear memory extinction. Here we report that, as happens with its consolidation, extinction of IA long-term memory requires activity of the p38 subfamily of mitogen-activated protein kinases (MAPK) in the CA1 region of the dorsal hippocampus. Moreover, we found that inhibition of hippocampal p38MAPK blocked memory reacquisition after extinction without affecting either the increase in IA memory retention induced by a second training session or animal's locomotor/exploratory activity and anxiety state.
authors.affiliation: Centro de Memória, Instituto de Pesquisas Biomédicas, Pontifícia Universidade Católica do Rio Grande do Sul, Av Ipiranga 6600, Porto Alegre, RS 90035-017, Brazil.
authors.forename: J I
authors.initials: JI
authors.lastname: Rossato
authors.forename: L R M
authors.initials: LR
authors.lastname: Bevilaqua
authors.forename: R H
authors.initials: RH
authors.lastname: Lima
authors.forename: J H
authors.initials: JH
authors.lastname: Medina
authors.forename: I
authors.initials: I
authors.lastname: Izquierdo
authors.forename: M
authors.initials: M
authors.lastname: Cammarota
mesh_terms: D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology*; D001522:Behavior, Animal; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005106:Exploratory Behavior / Q000187:drug effects; D005108:Extinction, Psychological / Q000187:drug effects / Q000502:physiology*; D006624:Hippocampus / Q000187:drug effects / Q000201:enzymology*; D007093:Imidazoles / Q000494:pharmacology; D007266:Inhibition, Psychological; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects; D013997:Time Factors; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D007093:Imidazoles; D011725:Pyridines; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580