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Dopaminergic Plasticity in the Bilateral Hippocampus Following Threat Reversal in Humans

Authors
  • Lissemore, Jennifer I.1
  • Nagano-Saito, Atsuko1
  • Smart, Kelly1
  • Gravel, Paul1, 2
  • Leyton, Marco1, 2
  • Benkelfat, Chawki1, 2
  • 1 McGill University, 1033 Pine Avenue West, Montreal, Quebec, H3A 1A1, Canada , Montreal (Canada)
  • 2 McConnell Brain Imaging Center, Montreal Neurological Institute, McGill University, 3801 University St., Montreal, Quebec, H3A 2B4, Canada , Montreal (Canada)
Type
Published Article
Journal
Scientific Reports
Publisher
Springer Nature
Publication Date
May 06, 2020
Volume
10
Issue
1
Identifiers
DOI: 10.1038/s41598-020-63977-7
Source
Springer Nature
License
Green

Abstract

When a cue no longer predicts a threat, a diminished ability to extinguish or reverse this association is thought to increase risk for stress-related disorders. Despite the clear clinical relevance, the mediating neurochemical mechanisms of threat reversal have received relatively little study. One neurotransmitter implicated in rodent research of changing associations with threat is dopamine. To study whether dopamine is involved in threat reversal in humans, we used high-resolution positron emission tomography (PET) coupled with 18F-fallypride. Twelve healthy volunteers (6 F/6 M) underwent three PET scans: (i) at baseline, (ii) following threat conditioning (the response to a cue associated with electric wrist shock), and (iii) following threat reversal (the response to the same cue now associated with safety). We observed moderate evidence of reduced dopamine D2/3 receptor availability, consistent with greater dopamine release, in the bilateral anterior hippocampus following threat reversal, in response to a safety cue that was previously associated with threat, as compared to both baseline and during exposure to the same cue prior to threat reversal. These findings offer the first preliminary evidence that the response to a previously threatening cue that has since become associated with safety involves dopaminergic neurotransmission within the hippocampus in healthy humans.

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