Implication of dopaminergic modulation in operant reward learning and the induction of compulsive-like feeding behavior in Aplysia

  1. Romuald Nargeot1,2,3
  1. 1Institut de Neurosciences Cognitives et Intégratives d’Aquitaine (INCIA), Université de Bordeaux, UMR 5287, F-33000 Bordeaux, France
  2. 2Centre National de la Recherche Scientifique (CNRS), UMR 5287, F-33000 Bordeaux, France

    Abstract

    Feeding in Aplysia provides an amenable model system for analyzing the neuronal substrates of motivated behavior and its adaptability by associative reward learning and neuromodulation. Among such learning processes, appetitive operant conditioning that leads to a compulsive-like expression of feeding actions is known to be associated with changes in the membrane properties and electrical coupling of essential action-initiating B63 neurons in the buccal central pattern generator (CPG). Moreover, the food-reward signal for this learning is conveyed in the esophageal nerve (En), an input nerve rich in dopamine-containing fibers. Here, to investigate whether dopamine (DA) is involved in this learning-induced plasticity, we used an in vitro analog of operant conditioning in which electrical stimulation of En substituted the contingent reinforcement of biting movements in vivo. Our data indicate that contingent En stimulation does, indeed, replicate the operant learning-induced changes in CPG output and the underlying membrane and synaptic properties of B63. Significantly, moreover, this network and cellular plasticity was blocked when the input nerve was stimulated in the presence of the DA receptor antagonist cis-flupenthixol. These results therefore suggest that En-derived dopaminergic modulation of CPG circuitry contributes to the operant reward-dependent emergence of a compulsive-like expression of Aplysia’s feeding behavior.

    Footnotes

    • 3 Corresponding author

      E-mail romuald.nargeot{at}u-bordeaux2.fr

    • [Supplemental material is available for this article.]

    • Received October 26, 2012.
    • Accepted April 4, 2013.
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