Research Report Anisomycin infusion in amygdala impairs consolidation of odor aversion memory Bertrand Desgranges, Frédéric Lévy, Guillaume Ferreira ⁎ Laboratoire de Comportement, Neurobiologie et Adaptation, UMR6175, INRA-CNRS-Université de Tours-Haras Nationaux, F-37380 Nouzilly, France ARTICLE INFO ABSTRACT Article history: Accepted 27 July 2008 Available online 12 August 2008 Conditioned odor aversion (COA) results from the association between a novel odor and a delayed visceral illness. Basolateral amygdala is crucial for COA learning but its importance in COA consolidation remains to be demonstrated. We investigated whether infusion of anisomycin, a protein synthesis inhibitor, in the basolateral amygdala impaired COA consolidation. COA was greatly impaired when anisomycin was infused immediately before odor–malaise pairing, but not between odor and malaise. This suggests that the formation of odor representation, rather than malaise integration, within the amygdala has been disrupted. Anisomycin infusion before acquisition did not affect short-term memory (tested 4 h after odor–malaise pairing) but dramatically impaired long-term COA memory (tested 3 days later). This indicates specific consolidation impairment. Control experiments indicated that anisomycin infusion did not affect amygdala functionality and olfactory perception and did not induce cell death in the amygdala. Moreover, anisomycin treatment induced an important decrease (65–70%) of LiCl-induced Fos protein expression in the basolateral and the central nuclei of the amygdala but not in adjacent piriform cortex indicating a reliable and localized protein synthesis inhibition. These findings suggest the pivotal role of the basolateral amygdala, and possibly the central amygdala, in COA memory consolidation. © 2008 Elsevier B.V. All rights reserved. Keywords: Conditioning Learning Flavor Olfaction Taste Rat 1. Introduction Avoidance of a toxic food is one of the most basic and oldest behaviors existing. It can be found in almost all animal species. The recognition and avoidance of the toxic food mainly depend on associative learning between the food's flavor (taste and/or odor; conditioned stimulus, CS) and its negative post-ingestion consequences, i.e. visceral illness (unconditioned stimulus, US; for reviews: Garcia et al., 1985; Bures, 1998). Taste was long considered the critical CS for food aversion because conditioned taste aversion (CTA) tolerates a long interval between taste and illness of several hours, whereas conditioned odor aversion (COA) can only be obtained if the delay between odor (presented close but outside to the drink- ing spout) and illness was kept very short (Hankins et al., 1973; Palmerino et al., 1980; Ferry et al., 1996). This behavioral characteristic, in addition to the important overlapping in the neural pathways involved in gustatory and visceral processing BRAIN RESEARCH 1236 (2008) 166 – 175 ⁎ Corresponding author. Fax: +33 2 47 42 77 43. E-mail address: ferreira@tours.inra.fr (G. Ferreira). Abbreviations: Ani, anisomycin; BLA, basolateral nucleus of the amygdala; BSA, bovine serum albumin; CeA, central nucleus of the amygdala; COA, conditioned odor aversion; CTA, conditioned taste aversion; CS, conditioned stimulus; Iso, isoamyl acetate; LiCl, lithium chloride; NeuN, neuronal nuclei protein; PBS, phosphate-buffered saline; Sal, Saline; US, unconditioned stimulus 0006-8993/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.brainres.2008.07.123 available at www.sciencedirect.com www.elsevier.com/locate/brainres