Novelty-evoked elevations of nucleus accumbens dopamine: dependence on impulse flow from the ventral subiculum and glutamatergic neurotransmission in the ventral tegmental area

Authors

  • Mark Legault,

    1. Center for Studies in Behavioural Neurobiology, Department of Psychology, Concordia University, Montreal, Quebec, Canada, H3G 1M8, Canada
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    • *Present address: Centre de Recherche Fernand Seguin, Université de Montréal, 7331 Hochelaga, Montréal, Quebec, H1N 3V2, Canada
  • Roy A. Wise

    1. Center for Studies in Behavioural Neurobiology, Department of Psychology, Concordia University, Montreal, Quebec, Canada, H3G 1M8, Canada
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    • Present address: Behavioural Neuroscience Branch, Intramural Research Program, National Institute on Drug Abuse (NIDA), National Institutes of Health, USA

: Dr M. Legault, at 1Centre de Recherche Fernand Seguin, Université de Montréal (see Present address, below)
Email: Mark.Legault@CRFS.Umontreal.ca

Abstract

In vivo microdialysis in freely moving rats was used to monitor novelty-evoked elevations in extracellular dopamine in the nucleus accumbens septi (NAS) and to examine the role of the ventral subiculum of the hippocampus and glutamatergic transmission in the ventral tegmental area (VTA) on these elevations. Exposure to novel stimuli evoked investigatory activity and increased nucleus accumbens dopamine. Unilateral injections of the sodium channel blocker tetrodotoxin (0.16 ng/0.5 µL) into the ventral subiculum ipsilateral to the dialysed NAS abolished novelty-evoked elevations in dopamine. Injections of tetrodotoxin into the contralateral VS did not prevent novelty-evoked elevations in nucleus accumbens dopamine. Unilateral perfusion (via microdialysis) of the ionotropic glutamate receptor antagonists kynurenic acid (1 mm) into the ipsilateral but not the contralateral VTA blocked novelty-evoked elevations in nucleus accumbens dopamine. Neither unilateral injections of tetrodotoxin nor unilateral perfusion of kynurenic acid disrupted investigatory behaviour. These data indicate that phasic elevations in nucleus accumbens dopamine evoked by exposure to unconditioned novel stimuli are dependent on impulse flow from the hippocampus and glutamatergic transmission in the VTA.

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