Cell Types in the Bed Nucleus of the Stria Terminalis: Effectors for Stress Modulation of Anxiety Open Access

Daniel, Sarah Elizabeth (2016)

Permanent URL: https://etd.library.emory.edu/concern/etds/7p88cg64w?locale=en


The anterolateral group of the bed nucleus of the stria terminalis (BNSTALG) is a complex brain structure that plays a crucial role in regulating anxiety. It contains multiple sub-regions composed of neurons expressing a range of neuropeptides and receptors. The heterogeneous nature of the BNSTALG, in which sub-regions such as the oval BNST (ovBNST) and anterodorsal BNST (adBNST) modulate anxiety in opposing ways, creates two opposing circuits. Understanding the intrinsic circuitry of the BNSTALG and how this circuitry may be affected by stress will be key to understanding anxiety in both a normal and pathological state. Previous work has defined three distinct cell types in the BNSTALG, namely Type I, Type II, and Type III cells, based on their electrophysiological response to hyperpolarizing and depolarizing current injections and mRNA expression profile. However, little is known about how these neurons contribute to the opposing pathways that facilitate and attenuate anxiety behavior. In this dissertation, we extend the characterization of the cell types in the BNSTALG with the goal of learning how these groups of neurons act together to affect anxiety behavior. First, we explore differences in electrophysiological cell types across species and regions in the BNSTALG. Type I-III cells were first described in rats, but no study has examined the electrophysiological properties of the cells in the mouse or primate BNSTALG. To this end, we compare the electrophysiological and morphological properties of BNSTALG neurons in the mouse, rat, and rhesus macaque. The mouse and primate BNSTALG contain cells that closely fit the description of Type I-III cells in the rat, however they are observed in significantly different proportions and do not all fit into these classification schemes. These data suggest there may be significant differences in the organization of the BNSTALG across species, however future studies will need to examine these differences further. The BNSTALG is composed of multiple regions, including the ovBNST and adBNST that have differential effects on anxiety. In the third chapter, we compare the cell types found in these two regions and show differential expression of cell types and electrophysiological properties between the ovBNST and adBNST. Finally, the fourth chapter seeks to explore the effects of chronic shock stress on the cell types in the BNSTALG. Although different cell types are thought to play opposing roles in the anxiety circuit, the effects of stress are often investigated with out an attempt to distinguish separate cell types. Here, we show multiple effects of stress on the electrophysiological and mRNA expression profile of cells in the BNSTALG, however, no effect of stress was observed in all cell types. Specifically Type III cells represent a population of corticotropin releasing factor (CRF) neurons that are uniquely sensitive to chronic stress. These results support the study of individual cell types to gain a better understanding of the circuits within the BNSTALG. We can then use the understanding of these circuits to explore better therapeutic interventions for pathological anxiety.

Table of Contents

Chapter 1: Stress modulation of opposing circuits in the bed nucleus of the stria terminalis

Abstract. 1

Introduction. 2

Interaction of Stress with Neuromodulators. 4

Corticotropin Releasing Factor. 4

Norepinephrine. 15

Dopamine. 24

Serotonin. 32

Stress Modulation of Synaptic Plasticity. 44

Clinical Implications. 52

Future Research Directions. 54

Chapter 2: Comparison of neurons in the BNSTALG in the mouse, rat, and rhesus macaque. 57

Introduction. 58

Methods. 60

Animal Subjects. 60

Preparation of BNST slices. 61

General patch clamp recording procedures. 62

Neuronal morphology. 64

Statistical Analysis. 65

Results. 66

Comparison of this rat sample with previous published samples. 66

Distribution of cell types in the mouse. 69

Distribution of cell types in the rhesus macaque. 71

Type I cells. 74

Type II cells. 75

Type III cells. 77

Morphology and Input Resistance. 78

Discussion. 80

Chapter 3: Comparison of cell types in the oval and anterodorsal BNST. 87

Introduction. 88

Methods. 89

Animal Subjects. 89

Preparation of BNST slices. 90

General patch clamp recording procedures. 90

Neuronal morphology. 93

Single cell RT-PCR. 94

Test of Thy1-Cre mouse line. 95

Statistical analysis. 96

Results. 97

Comparison of cell types in the oval and anterodorsal BNST in the rat. 97

Characterization of a novel subpopulation of neurons in Thy1-YFP transgenic mice. 101

Discussion. 107

Chapter 4: Chronic stress differentially affects Type III neurons in the bed nucleus of the stria terminalis. 121

Introduction. 122

Methods. 124

Animal Subjects. 124

Chronic stress and behavioral testing. 124

Electrophysiology. 128

Single-cell quantitative PCR. 134

Statistical Analysis. 137

Results. 138

Context fear and anxiety-like behavior. 139

Effect of stress on other electrophysiological properties of BNST neurons. 140

AMPA-to-NMDA ratio and AMPA rectification. 144

Effect of stress on CP-AMPA receptors in Type III and non-Type III cells. 145

Effect of stress on gene expression. 147

Discussion. 151

Effect of CSS on context fear and anxiety-like behavior. 152

Effect of stress on electrophysiological properties and genetic expression in Type III cells. 154

AMPA-to-NMDA ratio. 160

AMPA Rectification and CP-AMPARs. 161

Differences in expression of NMDA receptor subunits. 164

Conclusion. 166

Chapter 5: Conclusion and Future Directions.n169

Literature Cited. 181

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