The effects of norepinephrine microinjections into the central nucleus of the amygdala on serotonergic activity in the dorsal

Kolisch, Erika

Undergraduate Honors Thesis

The effects of norepinephrine microinjections into the central nucleus of the amygdala on serotonergic activity in the dorsal Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/undergraduate_honors_theses/4f16c3438

Abstract

The central nucleus of the amygdala (CE) projects to target areas that elicit autonomic and behavioral symptoms of fear. It has been shown that in stressful or fearful paradigms, endogenous norepinephrine (NE) is released into the CE. Microinjections of NE into the CE could activate fear circuits in the brain and lead to fear-like behavior. The CE projects to an area of the brain called the dorsal raphe nucleus (DR), specifically the dorsal raphe nucleus, ventrolateral part (DRVL) and the adjacent ventrolateral periaqueductal gray (VLPAG). We hypothesize that NE binds to adrenergic receptors in the CE to stimulate corticotropin-releasing factor (CRF) projections to the DR, where CRF binds to CRF type 2 receptors (CRFR2), which can elicit freezing behavior through serotonergic projections to a multisynaptic circuit controlling somatomotor neurons in the spinal cord. To test this hypothesis, we gave bilateral microinjections of NE (250 nmoles in 0.2 µL per side) into the CE and then immediately measured freezing behavior using the open-field test paradigm. Norepinephrine microinjections into the CE increased both the frequency and duration of freezing behavior. As the project is currently in the process of completion, we hope to also show that serotonergic neurons in the DR were activated in projection areas associated with previously established fear circuitry. This study was conducted to gain insight into control of serotonergic pathways that could lead to advancement of our understanding of stress-related mental illnesses.

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