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Control of the Endocrine Stress Response in Goldfish (Carassius auratus)

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Title: Control of the Endocrine Stress Response in Goldfish (Carassius auratus)
Author: Lim, Jan Edward
Department: Department of Integrative Biology
Program: Integrative Biology
Advisor: Bernier, Nicholas J.
Abstract: The purpose of this study was to obtain a deeper understanding the serotonergic control of the hypothalamic-pituitary-interrenal (HPI) stress axis and characterize a neuronal and behavioural response to a known stressor, using goldfish (Carassius auratus) as a model. The first part of this study investigated the serotonergic control of the HPI stress axis. In vivo injections of the serotonin (5-HT1A/7) receptor agonist 8-OH-DPAT resulted in significant and sustained increases in plasma cortisol without any changes in the mRNA abundance of brain corticotropin-releasing factor (CRF) and pituitary pro-opiomelanocortin or plasma adrenocorticotropic hormone levels. In vitro superfusion experiments of head kidney tissue showed that 5-HT can directly stimulate cortisol synthesis from the interrenals via several 5-HT receptor subtypes. Finally, double-labeling with anti-tyrosine hydroxylase and anti-5-HT revealed that the chromaffin cells of the head kidney contain 5-HT. The second part of the study investigated the goldfish response to a known stressor, the alarm pheromone. Alarm pheromone exposure resulted in an inhibition of movement and exploration and in suppression of neuronal activity in the pars parvocellularis of the nucleus preopticus, a brain region with extensive CRF immunolabelling. Overall, the results from this thesis suggest that in goldfish 5-HT may be involved in the paracrine regulation of cortisol secretion and that the CRF neurons of the pars parvocellularis play a role in mediating the stress response to alarm pheromones.
Date: 2013-09
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