Norepinephrine and Dopamine Contribute to Distinct Repetitive Behaviors Induced by Predator Odor Stress Open Access

Abstract

Exposure to stressful stimuli, such as novel environments or shock, elicits repetitive and

defensive behaviors in mice, many of which are mediated by the catecholamine

neurotransmitters norepinephrine (NE) and dopamine (DA). Dbh -/- mice lack the enzyme

dopamine-beta-hydroxylase (DBH), which converts DA to NE. Thus, these mice lack NE and

have elevated levels of DA as compared to NE-competent controls. We investigated the

repetitive behavioral responses of Dbh -/- mice and their NE-competent littermates (Dbh +/-) to

predator odor exposure. We found that while Dbh +/- mice engage in vigorous defensive burying

in the presence of predator odor but not water, Dbh -/- show higher levels of grooming,

regardless of the environment, and very little defensive burying in the presence of predator odor.

Pharmacological blockade of NE neurotransmission through alpha-1, alpha-2, and beta

adrenoreceptors decreased defensive burying in Dbh +/- mice, while blockade of DA

neurotransmission through D1 receptors decreased grooming in Dbh -/- mice. Together, these

results suggest that NE transmission is required for predator odor stress-induced defensive

burying, while DA transmission through D1 receptors facilitates grooming. These results shed

light on the neurochemistry that contributes to innate responses to psychological stress and may

help identify neurotransmitters and circuits that underlie repetitive behaviors that are exacerbated

by stress, as seen in neuropsychiatric disorders like Tourette’s syndrome, obsessive-compulsive

disorder, and autism spectrum disorder.

Table of Contents

Introduction………...............................................…………………………………………………………..……………………1

Methods……………………………….................................................……………………………………………………………4

Results………………………………….................................................……………………………………………..……………7

Discussion………………………………................................................……………………………………….……………….12

Figures………………………………….................................................…………………………………………………………19

Figure 1: Effect of predator odor compared to water in a novel environment……...........................................……19

Table 1: Comparison of Dbh +/- and Dbh -/- mice behavior in presence of predator odor vs. water……………………………………………...………………….......................................................................………..20

Figure 2: Effect of adrenergic receptor antagonists on light digging in the presence of predator odor in Dbh +/- mice.………………………..................................................................................................……………………..……21

Figure 3: Effect of adrenergic receptor antagonists on defensive burying in the presence of predator odor in Dbh +/- mice. …………………....................................................................................................………………...……..……22

Figure 4: Effect of adrenergic receptor antagonists on total digging in the presence of predator odor in Dbh +/- mice. ……………….................................................................................................……………………...……..……23

Figure 5: Effect of adrenergic receptor antagonists on grooming in the presence of predator odor in Dbh +/- mice.……………….........................................................................................................…………….………………24

Figure 6: Effects of dopamine receptor antagonists on light digging in Dbh -/- mice in the presence of predator odor. …………………………………..…………...............................................................................................………25

Figure 7: Effects of dopamine receptor antagonists on defensive burying in Dbh -/- mice in the presence of predator odor. ……………......................................................................................……………..……………….……26

Figure 8: Effects of dopamine receptor antagonists on total digging in Dbh -/- mice in the presence of predator odor. …………............................................................................................…………..……………………………...…27

Figure 9: Effects of dopamine receptor antagonists on grooming in Dbh -/- mice in the presence of predator odor.………………...............................................................................................…………………………...……..…28

Figure 10: Effects of a1-adrenergic receptor antagonism receptor on behavior in Dbh -/- mice in the presence of predator odor. ……….............................................................................................…………..………………………29

Figure 11: Effects of the D1 antagonist SCH-23390 on behaviors in Dbh +/- mice in the presence of predator odor.............................................................................................…………..…………………..………….......………30

References………………………………………………………………………………………..…………..…………..………………..31

About this Honors Thesis

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School	Emory College
Department	Neuroscience and Behavioral Biology
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Biology, Neuroscience
Keyword	Predator Odor Stress Norepinephrine Dopamine Repetitive Behaviors
Committee Chair / Thesis Advisor	Weinshenker, David, Emory University
Committee Members	Taliaferro-Smith, LaTonia, Emory University Lennard, Paul, Emory University

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