Peptides, corticotrophin pituitary hormones

Two neuropeptides, corticotrophin-releasing hormone (CRH) and arginine vasopressin (AVP) are released from parvoceUular neurons in the hypothalamic PVN to initiate a stress response. The terminal endings of these neurons, located in the median eminence of the hypothalamus, release CRH and AVP into the hypothalamic-hypophysial portal vessel system, where they travel to the anterior pituitary. The two neuropeptides act syn-ergistically on pituitary corticotrophs to activate the synthesis of pro-opiomelanocortin (POMC). This peptide, discussed in detail below, is processed to produce several peptides including adrenocorticotrophic hormone (ACTH), or corticotropin. ACTH released from corticotrophs travels via the bloodstream to act on cells in the zona fasciculata layer of the adrenal cortex, stimulating the synthesis and release of the glucocorticoids, cortisol (in humans) or corticosterone (in rodents). 

Corticotrophin releasing hormone (CRH), a peptide synthesised in the paraventricular nucleus, suppresses appetite and food intake in addition to its role in the regulation of the hypothalamic-pituitary-adrenal axis. 

Other pituitary hormones. It is hoped that the amino acid sequence of these peptides will soon be determined and thus that the chemical nature of the corticotrophin-releasing factor(s) will finally be elucidated. Of course, this type of method may also be of considerable potential value in the identification of other hypothalamic hormones. 

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