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Show 7 as well as specification and differentiation of neuroendocrine hypothalamic neurons. Molecules and signaling pathways that function in these processes were reviewed recently (Bedont et al., 2015; Burbridge et al., 2016). Particularly, Wnt signaling plays an early patterning role in the posteriorization of both zebrafish and mice hypothalamus (Bedont et al., 2015; Burbridge et al., 2016). Since it is known that zebrafish lef1 mutant does not appear to have an early hypothalamic defect in induction and patterning (Wang et al., 2012), my dissertation will instead focus on hypothalamic neurogenesis that includes neuronal specification and differentiation, which will be covered later in this chapter. 1.3.1.3 The hypothalamic-pituitary axis The hypothalamus, the pituitary gland and their interaction constitute the neuroendocrine hypothalamic-pituitary axis, which links between the CNS and the endocrine system (Löhr and Hammerschmidt, 2011). This axis can be subdivided into the hypothalamic-pituitary-adrenal (HPA) axis; the hypothalamic-pituitary-thyroid (HPT) axis; and the hypothalamic-pituitary-gonadal (HPG) axis (Löhr and Hammerschmidt, 2011). While these axes have complex interconnected functions, they all have their bestknown functions, with the HPG axis for reproduction, the HPT axis for metabolism, and the HPA axis for stress and immune response (Löhr and Hammerschmidt, 2011). In response to stress, corticotropin-releasing hormone (CRH) in the PVH of the hypothalamus initiates the HPA axis by activating its receptor in the pituitary and the release of adrenocorticotropic hormone (ACTH) into the blood stream, which ultimately stimulates synthesis and secretion of glucocorticoid (cortisol in human and fish; corticosterone in rodents) from the adrenal cortex (Smith and Vale, 2006). Stress-activated |
