Modification of Neural Activity in the Rostral Region of the Posterior Hypothalamus in Response to Stress Habituation

Undergraduate Honors Thesis

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Citeable URL: https://scholar.colorado.edu/concern/undergraduate_honors_theses/cr56n270m

Abstract

Excessive or chronic stress is correlated with many common physical and mental disorders. With stress being a widespread experience in today’s society, the ability to adapt to stress is important to limit its cumulative harmful impact. One form of adaptation is stress habituation, where a reduction in both sympathetic nervous system and hypothalamic-pituitary-adrenal axis activation is seen in response to repeated presentations of the same (homotypic) stressful situation over time. The neural mechanism of habituation is poorly understood, but evidence points towards involvement of the rostral region of the posterior hypothalamus (rPH) contributing to the habituation process. This study is interested in confirming that role by measuring calcium influx, as an index for neuronal activity, in the rPH of Sprague Dawley rats before and after audiogenic stress habituation. Calcium influx was measured using GCaMP by detecting fluorescence emission from Green Fluorescent Protein as calcium ions enter the cell and the intensity of fluorescence was evaluated using fiber photometry. The rPH was observed to have a reduction in calcium signaling from before to after habituation to a loud noise stressor, but that reduction was not observed for stimuli that were not repeatedly presented. With the calcium signal reduction interpreted as a reduction in the region’s activity, this study provides additional evidence that the rPH contributes to the mechanism of stress habituation.

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