Date of Award

5-1-2014

Degree Type

Dissertation

University or Center

Clark Atlanta University(CAU)

Degree Name

Ph.D.

Department

Biology

First Advisor

Dr. Chuma O. Okere

Abstract

The inner workings of the smallest neural structures have been mysterious in function since they were discovered. Even more interesting are the modes and methods by which an internal reaction is waged as a result of an external stimulus. This is especially true if the stimulus is not inherently or physically painful or harmful, but rather emotional. Stress, for example has a major deleterious effect on the brain. However, exactly how different brain regions work together to react to stress is largely unknown. The primary goal of this study was to further understand how neurons within the topography of the paraventricular nucleus (PVN) and supraoptic nucleus (SON) of the brain's hypothalamus are altered during the whole-organism stress response. A significant proportion of PVN and SON cells are made up of nitric oxide (NO) synthase (NOS)-containing neu rons. Previous studies have shown that a single acute restraint paradigm differentially ac tivates NO-producing endogenous machinery within these hypothalamic areas. However, the temporal activation profile of restraint-induced NOS reactivity within the PVN and SON remains to be clearly determined. In this study, several techniques were used in cluding the following: nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d, a histochemical NOS index), im- munohistochemistry for Fos, caspase acti vated DNAase (CAD, an enzyme that cleaves chromosomal DNA in apoptotic cells), and phosphorylated extracellular signal-regulated kinase (pERKl/2; a signaling pathway preferentially activated in response to growth factors and regulator of cell proliferation and differentiation). We have analyzed the pattern of this neural activation in response to stress in adult male Wistar rats in the SON and PVN after the animals were placed in a restraint device for one-, three- or six- hours and compared the results to those of unre strained rats. The aim was to determine the temporal profile of restraint-induced activa tion of the NO production machinery within the SON and PVN. As Recruitment of neuronal pools is a well-recognized concept of the function of hypothalamic neurons. The present observations suggest a progressive recruitment of nitrergic neurons within these neuronal domains during whole animal exposure to stress. In sum, the data from the pre sent observations extend our understanding of the discrete temporal reorganization of the PVN and SON and their involvement in signal processing during the stress response.

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