Corticotropin-releasing hormone physiology

Abstract

Corticotropin-releasing hormone (CRH), also known as corticotropin-releasing factor, is a highly conserved peptide hormone comprising 41 amino acid residues. Its name derives from its role in the anterior pituitary, where it mediates the release of corticotropin (ACTH) leading to the release of adrenocortical steroids. CRH is the major hypothalamic activator of the hypothalamic-pituitaryadrenal (HPA) axis. Major functions of the HPA include: (i) influencing fetal development of major organ systems including lung, liver, and gut, (ii) metabolic functions, including the maintenance of normal blood glucose levels during the fasting state via glycogenolysis and gluconeogenesis, (iii) modulation of immune function, and (iv) maintenance of cardiovascular tone. In addition, CRH, acting both directly and via the HPA, has a role in regulating several neuroendocrine functions including behavior, food intake, reproduction, growth, immune function, and autonomic function. CRH has been localized to the paraventricular nucleus (PVN) of the hypothalamus, which projects to the median eminence and other hypothalamic and midbrain targets. The CRH gene is composed of two exons. The CRH promoter contains a cAMP-response element, and the intron contains a restrictive element-1/neuron restrictive silencing element (RE-1/NRSE) sequence. Recently, a family of CRH-related peptides, termed the urocortins, has been identified. These peptides probably play a role in integrating multiple aspects of the stress-response, although their functions are largely unknown. Both CRH and the urocortins interact with two transmembrane G-protein-coupled cell surface receptors, CRH-R1, and CRH-R2, which differ in their patterns of tissue distribution. In addition, the binding affinities for CRH and the urocortins to the two receptors differ considerably, and may contribute to the different actions of these peptides.European Journal of Endocrinology 155 S71-S76

Regulation of the Hypothalamic-Pituitary-Adrenal Axis

“…CRH has existed, as an endogenous signaling molecule, even prior to the evolution of tetrapods and teleosts delineating its crucial role in the maintenance of the homeostasis of the organism. The hypophysiotropic CRH neurons are located in the parvicellular division of PVN (pPVN) in the hypothalamus and project to the external layer of the median eminence, releasing CRH into the hypophysial-portal circulation; however, some CRH fibers in the PVN also project to the brainstem [14] . Non-hypophysiotropic CRH neurons are abundant primarily in limbic structures, such as amygdala, locus coeruleus, involved in the procession of sensory information and in the regulation of the autonomic nervous system.…”

The Origin of Remote Symptoms in Electrical and Lightning Injuries: An Attempt at Explanation and a Hypothesis for Testing

“…Recently, a family of CRH-related peptides, termed the urocortins, has been identified. These peptides probably play a role in integrating multiple aspects of the stress-response, although their functions are largely unknown" [14].…”

“…Although the exact inputs to the hypothalamus are not known, these neurons are largely controlled by serotoninmediated input from the amygdala and hippocampus of the limbic system [14]. It is interesting to note, again in passing, that serotonin is one of the key mono-amines depleted in depression.…”

Identification and characterization of a novel corticotropin‐releasing hormone‐binding protein (CRH‐BP) gene from Chinese honeybee (Apis cerana cerana)

“…The corticotropin-releasing hormone (CRH), also known as corticotropin-releasing factor (CRF), is a neuroendocrine peptide that regulates various physiological responses to stresses (Seasholtz et al, 2002). Moreover, CRH is considered to act as a neurotransmitter to coordinate various autonomic, hormonal, and behavioral responses to stresses and also may be involved in developmental processes (Muglia et al, 1995;Cortright et al, 1997;Majzoub, 2006).…”

“…It has been reported that juvenile hormone, ecdysteriod and prothoracicotropic hormone are involved in the regulation of caste differentiation (Vitt and Hartfelder, 1998). Meanwhile, CRH regulates various hormonal and behavioral responses as a neurotransmitter in mammals (Majzoub, 2006). Considering that CRH which also functions as a crucial hormone in insect, we investigated the expression levels of AccCRH-BP among workers, queens, and drones of honeybees.…”