Neurohypophyseal

Table 1. Structures of the Neurohypophyseal Hormone-Like Peptides, ...

Several human receptors for the neurohypophyseal hormones have been cloned and the sequences elucidated. The human V2 receptor for antidiuretic hormone presumably contains 371 amino acids and seven transmembrane segments and activates cycHc AMP (76). The oxytocin receptor is a classic G-protein-coupled type of receptor with a proposed membrane topography also involving seven transmembrane components (84). A schematic representation of the oxytocin receptor stmcture within the membrane is shown in Eigure 4 (85). 

D. H. Schlesinger, ed.. Neurohypophyseal Peptide Hormones and Other Biologically Active Peptides, Developments in Endocrinology, Vol. 13, Elsevier Science, New York, 1981. 

The effects of both oxytocin and vasopressin are particularly responsive to reproductive steroids (Tables 7 and 8). Oxytocin and vasopressin are best known as neurohypophyseal peptides, released by the posterior pituitary. However, both peptides also are released within the nervous system. Receptors for oxytocin and vasopressin are distributed in areas of the CNS that have been implicated in reproduction, emotion and autonomic functions. 

M. Rholam and P. Nicolas, Conformational flexibility of neurophysin as investigated by local motions of fluorophores. Relationships with neurohypophyseal hormone binding,... 

Myometrial stimulants. The neurohypophyseal hormone oxytocin (p. 242) is given parenterally (or by the nasal or buccal route) before, during, or after labor in order to prompt uterine contractions or to enhance them. Certain prostaglandins or analogues of them (p. 

The endocrine system is controlled by the brain. Nerve cells of the hypothalamus synthesize and release messenger substances that regulate adenohy-pophyseal (AH) hormone release or are themselves secreted into the body as hormones. The latter comprise the so-called neurohypophyseal (NH) hormones. 

Carbamazepine stimulates antidiuretic hormone activity and has been used for the treatment of neurohypophyseal diabetes insipidus. Carbamazepine induces microsomal enzymes and its metabolism is subject to auto-induction. Frequently occurring adverse effects are sedation, dry mouth, dizziness and gastrointestinal disturbances. Photosensitivity reactions, urticaria and Stevens-Johnson syndrome have been described. The elderly are more prone to mental confusion, cardiac abnormalities and problems due to inappropriate ADH secretion. 

Historically vasopressin and oxytocin, two nonapep-tides, were the first peptide neurohormones to be considered they are stored in the neurohypophysis and released into the bloodstream upon an appropriate stimulus. In the periphery, oxytocin stimulates the contraction of epididymal and uterine smooth muscle (see Chapter 62) and vasopressin (antidiuretic hormone) facilitates the reabsorption of water from the kidney tubules. In addition to these well-accepted roles as neurohormones, there is convincing evidence that these compounds function as neurotransmitters they both possess potent inhibitory actions on neurohypophyseal neurons. The significance of their neurotransmitter function is not yet clear. 

Valtin H, Sawyer WH, Sokol HW (1965) Neurohypophyseal principles in rats homozygous and heterozygous for hypothalamic diabetes insipidus (Brattleboro strain). Endocrinology 77 701-706... 

Anterior and posterior pituitary are found together at the base of the skull, once the brain has been removed. The neurohypophyseal part (posterior pituitary) is discarded and the anterior pituitary is bisected to... 

Galfi M, Janaky T, Toth R, Prohaszka Gy, Juhasz A, Varga Cs, Laszlo FA (2001) Effects of dopamine and dopamine-active compounds on oxytocin and vasopressin production in rat neurohypophyseal tissue cultures. Reg Peptides 98 49-54. 

Lightman SL, Iversen LL, Forsling ML (1982) Dopamine and [D-ALA2, D-LEU5]enkephalin inhibit the electrically stimulated neurohypophyseal release of vasopressin in vitro evidence for calcium-dependent opiate action. J Neurosci 2 78-81. 

Pitzel L, Konig A (1984) Lack of response in the release of oxytocin and vasopressin from isolated neurohypophyses to dopamine, met-enkephalin and leu-enkephalin. Exp Brain Res 56 221-226. 

Steger RW, Juszczak M, Fadden C, Bartke A (1995) Photoperiod effects on neurohypophyseal and tuberoinfundibular dopamine metabolism in the male hamster. Endocrinology 736 3000-3006. 

These data show the presence in subesophageal and thoracic ganglia of Locusta of an antiparallel dimeric peptide (F2), which was called the AVP-like insect diuretic hormone (AVP-like DH) (H). The sequence homology between the AVP-like DH and the vertebrate neurohypophyseal peptides is strong Cys-(2)-(3)-(4)-Asn-Cys-Pro-(8)-Gly-NH2. The AVP-like DH and AVP differ only at positions 2, 3, and 4, whereas the homology to the ancestral molecule arginine vasotocin is even stronger, with differences restricted to positions 2 and... 

The posterior pituitaiy (ncurnhypophysis) is the source of vasoprc.ssin. oxytocin, a- and /8-MSH. and coherin. The synthesis, transport, and release of these hormones have been reviewed by Brownstein.- - Va.sopressin and oxytocin ore synthesized and relea.sed by neurons of the hypothalamic-neurohypophyseal system. Thc.se peptide hormones, and their respective neurophysin carrier proteins, are synthesized as structural components of separate precursor proteins, and these proteins appear to be partially degraded into... 

Bergman RN, Hechter O. Neurohypophyseal hormone-responsive renal adenylate cyclase. IV. A random-hit matrix model for coupline in a hormone-sensitive adenylate cyclase system. J Biol Chem 1978 253 3238-3250. 

The adenohypophysis secretes growth hormone (GH), prolactin (PRL), thyrotropin (TSH), adrenocorticotropin (ACTH), foUicle-stimulating hormone (FSH), and luteinizing hormone (LH), all of which are proteins or peptides (see Table 28-1 in Chapter 28). It also secretes P-lipotropin (P-LPH) and a number of smaller peptides of undetermined significance Vasopressin (also known as antidiuretic hormone [ADH]) and oxytocin are produced in the hypothalamus and are carried through the neurohypophyseal nerve axons to the neurohypophysis. Thus the neurohypophysis is not a discrete endocrine organ, but rather functions as a reservoir for these two hormones. 

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