Dopamine receptor activity participates in hippocampal synaptic plasticity associated with novel object recognition. (1st October 2016)

• Record Type: Journal Article
• Authors: Yang, Kechun; Broussard, John I.; Levine, Amber T.; Jenson, Daniel; Arenkiel, Benjamin R.; Dani, John A.
• Editors: Bolam, Paul
• Is Part Of: European journal of neuroscience. Volume 45:Number 1(2017)
• Page Start: 138
• Page End: 146
• Publication Date: 2016-10-01
• Subjects: AMPA/NMDA ratio -- CA1 -- dentate gyrus -- learning -- memory; Nervous system -- Periodicals; 612.8
• DOI: 10.1111/ejn.13406
• Languages: English
• ISSNs: 0953-816X

Abstract

Abstract: Physiological and behavioral evidence supports that dopamine (DA) receptor signaling influences hippocampal function. While several recent studies examined how DA influences CA1 plasticity and learning, there are fewer studies investigating the influence of DA signaling to the dentate gyrus. The dentate gyrus receives convergent cortical input through the perforant path fiber tracts and has been conceptualized to detect novelty in spatial memory tasks. To test whether DA‐receptor activity influences novelty‐detection, we used a novel object recognition (NOR) task where mice remember previously presented objects as an indication of learning. Although DA innervation arises from other sources and the main DA signaling may be from those sources, our molecular approaches verified that midbrain dopaminergic fibers also sparsely innervate the dentate gyrus. During the NOR task, wild‐type mice spent significantly more time investigating novel objects rather than previously observed objects. Dentate granule cells in slices cut from those mice showed an increased AMPA/NMDA‐receptor current ratio indicative of potentiated synaptic transmission. Post‐training injection of a D1‐like receptor antagonist not only effectively blocked the preference for the novel objects, but also prevented the increased AMPA/NMDA ratio. Consistent with that finding, neither NOR learning nor the increase in the AMPA/NMDA ratio were observed in DA‐receptor KO mice under the same experimental conditions. The results indicate that DA‐receptor signaling contributes to the successful completion of the NOR task and to the associated synaptic plasticity of the dentate gyrus that likely contributes to the learning. Abstract : Novel object recognition (NOR) engages the hippocampus as mice remember previously presented objects as an indication of learning. In this study, Yang et al . measured the ratio of AMPA to NMDA currents. When mice were exposed to novel objects (right), the AMPA/NMDA ratio increased in dentate granule neurons. Accurately performing the task and the associated increase in the AMPA/NMDA ratio were dependent upon D1‐like receptor activity.