Psychology ETDs

Publication Date

Spring 4-29-2019

Abstract

Previous research in rodents and humans has implicated the ventral hippocampus in regulating anxiety. However, many rodent studies examining ventral hippocampal neuronal pathways have utilized lesions that create nonspecific and/or nonreversible damage to the region. The present study sought to characterize the role of ventral hippocampal glutamatergic pyramidal neurons in modulating anxiety-like behavior during exposure to a variety of threatening stimuli. Five weeks prior to testing, male Long-Evans hooded rats received ventral hippocampal viral-vector infusions expressing either pAAV-CaMKIIα-hM4D-mCherry (DREADD) or pAAV-CaMKIIa-EGFP (GFP). DREADD transfection allowed for the specific, noninvasive and temporary inhibition of ventral hippocampal glutamatergic neurons immediately before threat presentation. Rats were evaluated for behaviors congruent with anxiety- or fear-like defensive states (e.g., freezing, risk assessment, avoidance, etc.) during testing in the elevated plus-maze and light-dark exploration test, or footshock-induced contextually conditioned fear, respectively. Analyses revealed a significant effect of DREADD inhibition that was dependent on the type of threat exposure. Specifically, compared to GFP controls, DREADD-induced silencing of ventral hippocampal glutamatergic neurons reduced anxiety-like behavior in the elevated plus-maze and light-dark test, without reliably affecting the expression of conditioned fear. The present results confirm that ventral hippocampal glutamatergic pyramidal neurons are recruited in rats during exposure to anxiety-inducing stimuli. These data add to a growing literature implicating the ventral hippocampus as a key region involved in modulating anxiety-like behaviors in rodents, primates and humans.

Degree Name

Psychology

Level of Degree

Masters

Department Name

Psychology

First Committee Member (Chair)

Nathan S. Pentkowski

Second Committee Member

Jonathan Brigman

Third Committee Member

Benjamin Clark

Language

English

Keywords

DREADD, CAMKIIa, glutamate, anxiety, hippocampus, defense

Document Type

Thesis

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