title: Inhibition of Wnt signalling dose-dependently impairs the acquisition and expression of amphetamine-induced conditioned place preference.
abstract: The mechanisms by which dopaminergic neurotransmission in the nucleus accumbens (NAc) is involved in incentive learning produced by rewarding stimuli remain unclear. Recently, Wnt signalling has been implicated in synaptic plasticity and learning and memory. Functional interactions between Wnt and dopamine (DA) signalling has been demonstrated using in vitro and tissue physiology approaches, however there remains a lack of in vivo research into the involvement of Wnt in DA-mediated learning in behaving animals. The present study assessed the role of Wnt signalling in DA-mediated incentive learning using the conditioned place preference (CPP) paradigm. We hypothesized that inhibition of Wnt with intra-NAc microinjections of Wnt palmitoylation inhibitor IWP-2 will dose-dependently block the acquisition and expression of amphetamine (AMPH)-induced CPP in rats. Intra-NAc IWP-2 (0.001, 0.05, 1.0 but not 0.0001μg/0.5μl/side) prior to conditioning with AMPH (20.0μg/0.5μl/side) blocked acquisition of CPP. Intra-NAc IWP-2 (0.05, 0.5, 1.0 but not 0.001μg/0.5μl/side) during test following conditioning with AMPH blocked expression but at a higher dose than was need to block acquisition. Sensitization of locomotor activity to AMPH was observed during conditioning and this effect was blocked in groups given IWP-2 prior to AMPH. However, intra-NAc IWP-2 during conditioning did not block the locomotor stimulant effects of AMPH. These results implicate Wnt in DA-mediated incentive learning and suggest that Wnt signalling may be more important for the acquisition of CPP then for its expression. However, mechanisms by which Wnt and DA signalling pathways interact to influence DA-mediated reward-related learning remain to be elucidated.
authors.affiliation: Centre for Neuroscience Studies, Queen's University, Kingston, ON, Canada. Electronic address: 14fi@queensu.ca.
authors.forename: Farhana
authors.initials: F
authors.lastname: Islam
authors.affiliation: Department of Psychology, Queen's University, Kingston, ON, Canada. Electronic address: kathleen.xu@queensu.ca.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Xu
authors.affiliation: Centre for Neuroscience Studies, Queen's University, Kingston, ON, Canada; Department of Psychology, Queen's University, Kingston, ON, Canada. Electronic address: beninger@queensu.ca.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Beninger
mesh_terms: D000661:Amphetamine / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D052160:Benzothiazoles / Q000008:administration & dosage / Q000494:pharmacology*; D003213:Conditioning, Psychological / Q000187:drug effects*; D004298:Dopamine / Q000502:physiology*; D015259:Dopamine Agents / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D009714:Nucleus Accumbens / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D012201:Reward; D015398:Signal Transduction; D051153:Wnt Proteins / Q000037:antagonists & inhibitors*
chemical_list: D052160:Benzothiazoles; D015259:Dopamine Agents; C000611186:IWP-2 compound; D051153:Wnt Proteins; D000661:Amphetamine; D004298:Dopamine
keywords: Amphetamine; Conditioned place preference; Dopamine; IWP-2; Reward-related learning; Wnt