title: Extinction learning, which consists of the inhibition of retrieval, can be learned without retrieval.
abstract: In the present study we test the hypothesis that extinction is not a consequence of retrieval in unreinforced conditioned stimulus (CS) presentation but the mere perception of the CS in the absence of a conditioned response. Animals with cannulae implanted in the CA1 region of hippocampus were subjected to extinction of contextual fear conditioning. Muscimol infused intra-CA1 before an extinction training session of contextual fear conditioning (CFC) blocks retrieval but not consolidation of extinction measured 24 h later. Additionally, this inhibition of retrieval does not affect early persistence of extinction when tested 7 d later or its spontaneous recovery after 2 wk. Furthermore, both anisomycin, an inhibitor of ribosomal protein synthesis, and rapamycin, an inhibitor of extraribosomal protein synthesis, given into the CA1, impair extinction of CFC regardless of whether its retrieval was blocked by muscimol. Therefore, retrieval performance in the first unreinforced session is not necessary for the installation, maintenance, or spontaneous recovery of extinction of CFC.
authors.affiliation: National Institute of Translational Neuroscience, National Research Council of Brazil, and Memory Center, Brain Institute of Rio Grande do Sul, Pontifical Catholic University of Rio Grande do Sul, 90610-000 Porto Alegre, RS, Brazil jociane_carvalho@hotmail.com izquier@terra.com.br.
authors.forename: Jociane
authors.initials: J
authors.lastname: de Carvalho Myskiw
authors.affiliation: National Institute of Translational Neuroscience, National Research Council of Brazil, and Memory Center, Brain Institute of Rio Grande do Sul, Pontifical Catholic University of Rio Grande do Sul, 90610-000 Porto Alegre, RS, Brazil.
authors.forename: Cristiane Regina Guerino
authors.initials: CR
authors.lastname: Furini
authors.affiliation: National Institute of Translational Neuroscience, National Research Council of Brazil, and Memory Center, Brain Institute of Rio Grande do Sul, Pontifical Catholic University of Rio Grande do Sul, 90610-000 Porto Alegre, RS, Brazil.
authors.forename: Bianca
authors.initials: B
authors.lastname: Schmidt
authors.affiliation: National Institute of Translational Neuroscience, National Research Council of Brazil, and Memory Center, Brain Institute of Rio Grande do Sul, Pontifical Catholic University of Rio Grande do Sul, 90610-000 Porto Alegre, RS, Brazil.
authors.forename: Flávia
authors.initials: F
authors.lastname: Ferreira
authors.affiliation: National Institute of Translational Neuroscience, National Research Council of Brazil, and Memory Center, Brain Institute of Rio Grande do Sul, Pontifical Catholic University of Rio Grande do Sul, 90610-000 Porto Alegre, RS, Brazil jociane_carvalho@hotmail.com izquier@terra.com.br.
authors.forename: Ivan
authors.initials: I
authors.lastname: Izquierdo
mesh_terms: D000818:Animals; D000841:Anisomycin / Q000008:administration & dosage; D056547:CA1 Region, Hippocampal / Q000187:drug effects / Q000502:physiology; D003213:Conditioning, Psychological / Q000502:physiology; D005108:Extinction, Psychological / Q000187:drug effects / Q000502:physiology*; D005239:Fear / Q000502:physiology / Q000523:psychology; D058785:GABA-A Receptor Agonists / Q000008:administration & dosage; D007858:Learning / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008959:Models, Neurological; D008960:Models, Psychological; D009118:Muscimol / Q000008:administration & dosage; D011500:Protein Synthesis Inhibitors / Q000008:administration & dosage; D051381:Rats; D017208:Rats, Wistar; D020123:Sirolimus / Q000008:administration & dosage
chemical_list: D058785:GABA-A Receptor Agonists; D011500:Protein Synthesis Inhibitors; D009118:Muscimol; D000841:Anisomycin; D020123:Sirolimus
keywords: contextual fear conditioning; fear extinction; hippocampus; retrieval; unreinforced conditioned stimulus