title: Disruption of the US pre-exposure effect and latent inhibition in two-way active avoidance by systemic amphetamine in C57BL/6 mice.
abstract: BACKGROUND
  Pre-exposure to either one of the two to-be-associated stimuli alone is known to reduce the efficiency of the learning of their association when they are subsequently paired explicitly. In classical conditioning, pre-exposure to the conditioned stimulus (CS) gives rise to latent inhibition (LI); and pre-exposure to the unconditioned stimulus (US) results in the US pre-exposure effect (USPEE). Considerable evidence supports an important role of central dopamine in the regulation and modulation of LI; it has been suggested that the USPEE may be similarly controlled by dopamine, but this parallelism has only been directly demonstrated in the conditioned taste aversion paradigm.
  
  
  OBJECTIVE
  The present study tested this hypothesis by comparing the efficacy of systemic amphetamine treatment to affect the expression of LI and the USPEE in a two-way active avoidance paradigm.
  
  
  METHODS
  C57BL/6 male mice were tested in active avoidance using a tone CS and a foot-shock US. Twenty-four hours before, they were pre-exposed to 100 presentations of the CS or the US, or to the test apparatus only. Amphetamine (2.5 mg/kg) or saline was administered before stimulus pre-exposure and conditioned avoidance test, in which the mice learned to avoid the shock by shuttling in response to the tone.
  
  
  RESULTS
  Amphetamine disrupted both stimulus pre-exposure effects, thus, lending further support to the hypothesis that the USPEE is similar to LI in its sensitivity to dopamine receptor agonist. Hence, the USPEE paradigm may represent a valuable addition to the study of dopamine-sensitive processes of selective learning currently implicated in LI and Kamin blocking.
authors.affiliation: Laboratory of Behavioural Neurobiology, ETH Zurich, Schorenstrasse 16, 8603, Schwerzenbach, Switzerland.
authors.forename: Tilly
authors.initials: T
authors.lastname: Chang
authors.forename: Urs
authors.initials: U
authors.lastname: Meyer
authors.forename: Joram
authors.initials: J
authors.lastname: Feldon
authors.forename: Benjamin K
authors.initials: BK
authors.lastname: Yee
mesh_terms: D000661:Amphetamine / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D001245:Association Learning / Q000187:drug effects; D001362:Avoidance Learning / Q000187:drug effects*; D001522:Behavior, Animal / Q000187:drug effects; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D003214:Conditioning, Classical / Q000187:drug effects; D004298:Dopamine / Q000378:metabolism; D015259:Dopamine Agents / Q000494:pharmacology*; D007266:Inhibition, Psychological; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL
chemical_list: D000697:Central Nervous System Stimulants; D015259:Dopamine Agents; D000661:Amphetamine; D004298:Dopamine