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A large body of evidence indicates that reactivation of aversive memories leads to protein synthesis-dependent memory reconsolidation which can be disrupted by cycloheximide (CHX) and other protein synthesis inhibitors. The aim of the present study was to investigate whether CHX would alter maintenance of well-trained instrumental responding for 0.1% saccharin. Male Wistar rats were trained to lever press for saccharin. When lever pressing stabilized, experimental self-administration sessions with CHX (3 mg/kg, s.c.) started. The animals received four experimental sessions, with each session separated by 5 days. The protein synthesis inhibitor was injected immediately after the experimental sessions 1-3. Repeated post-session injections of CHX did not alter saccharin self-administration. A two-bottle choice test conducted after the last experimental session revealed that CHX had not induced any conditioned taste aversion to 0.1% saccharin. The present results suggest that well-consolidated long-term memory of an appetitive instrumental task does not depend on de novo protein synthesis.

The Fos family of transcription factors may play a key role in various forms of brain plasticity. Among different genes coding Fos proteins is the fosB gene. Protein products of the fosB gene are thought to be critically involved in neural adaptations produced by chronic treatment with drugs of abuse. fosB gene transcription leads to accumulation of full-length FosB as well as its truncated form, deltafosB. Stable isoforms of deltafosB called chronic FRAs accumulate in the brain after chronic administration of various drugs of abuse. The purpose of the present study was to evaluate the role of the fosB gene in two-bottle choice ethanol self-administration. For this aim, ethanol (2-8% v/v) intake and preference was assessed in fosB mutant (n=17) and wild-type (WT) mice (n=16). For comparison, consumption of saccharin (0.05-0.8% w/v) and quinine (15-960 microM) solutions was assessed in the same animals. Ethanol preference in both groups varied from around 50% for the lowest to 20% for the highest ethanol concentration. Neither ethanol intake (g/kg) nor preference differed between the two genotypes. In contrast, saccharin preference, but not intake, was higher in the fosB mutants. Only slight and inconsistent between-group differences were observed in terms of quinine preference. The present results suggest that permanent elimination of fosB gene products does not alter ethanol intake but may enhance preference for sweet solutions in mice.

Abstract: A large body of evidence indicates that reactivation of aversive memories leads to protein synthesis-dependent memory reconsolidation which can be disrupted by cycloheximide and other protein synthesis inhibitors. The aim of the present study was to investigate whether cycloheximide would alter reconsolidation of the associations involving discrete cues paired with a sweet reward in an appetitive instrumental task. Rats trained to lever press for 0.1% saccharin were repeatedly tested for cue-induced reinstatement of non-reinforced responding for saccharin. CHX (3 mg/kg, s.c.) or its vehicle was injected immediately after each reinstatement session. The protein synthesis inhibitor did not alter the ability of the saccharin-paired cues to reinstate saccharin seeking. The present results suggest that passive re-exposure to saccharin-paired discrete cues in the reinstatement procedure does not lead to any cycloheximide-sensitive reconsolidation of the original associations. [Copyright &y& Elsevier]