Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In earlier ultrastructural studies of the supraoptic nucleus in adult rats we noted "free" and incompletely covered postsynaptic densities (collectively referred to here as vacant postsynaptic densities) on dendritic shafts. Free postsynaptic densities have been reported in other parts of the central nervous system of normal rodents. We investigated the possibility that physiological activation of the supraoptic cells, which produces changes in many aspects of their morphology, would alter the incidence of the free or incompletely covered postsynaptic densities on dendrites in the supraoptic basal dendritic zone. The cells of the supraoptic nucleus are activated to increase cell firing and secretion of oxytocin and/or vasopressin in response to dehydration, gestation, and lactation. We have examined: untreated virgin females; untreated males; 24 h water-deprived males; prepartum (21st day of gestation) females; postpartum females (on the day of parturition); lactating females (14 days of suckling); mothers 10 days after weaning their pups; females given 2% saline to drink (dehydrated) for 10 days; and females or males given 2% saline to drink for 10 days, then given tap water for 2 or 5 weeks to allow rehydration. Only long-term activation of the supraoptic nucleus by lactation or by drinking saline for 10 days brought about significant decreases in the percentage of dendrites with vacant postsynaptic densities. These densities did not reappear in saline treated rats which had been rehydrated for 2 weeks, but did return in both the 5-week rehydration and the 10-day postweaning groups.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Vacant postsynaptic densities on supraoptic dendrites of adult rats diminish in number with chronic stimuli. 373 Dec 49

These experiments were designed to characterize the nature and extent of diabetes insipidus present in a new model of genetic vasopressin (VP) deficiency, the Roman high avoidance rat homozygous for diabetes insipidus (RHA: di/di strain). The new strain was developed from an initial cross between Long-Evans derived Brattleboro (LE:di/di) rats and normal Roman high avoidance (RHA: +/+) rats, and has been bred to be congenic with the parent RHA: +/+ strain. RHA: di/di rats exhibited polydipsia, excreted dilute urine, and exhibited elevated plasma osmolality. RHA: di/di rats shows a similar urinary response to dehydration as LE: di/di rats. VP was undetectable by radioimmunoassay in the serum, brain, and neurohypophysis of RHA: di/di rats. VP-neurophysin containing cells were not observed in the brains of RHA: di/di rats upon immunocytochemical analysis. Thus, the new RHA: di/di strain exhibits essentially the same profile of diabetes insipidus as the LE: di/di rat. The congenic relationship between RHA: di/di and RHA: +/+ rats makes the RHA: di/di rat a useful model under circumstances where genetic variables unrelated to VP deficiency may confound the interpretation of data.
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PMID:Characterization of a new rodent model of diabetes insipidus: the Roman high avoidance rat homozygous for diabetes insipidus. 373 82

After dehydration, oral rehydration causes a fall in plasma arginine vasopressin (AVP) that precedes changes in plasma osmolality. To investigate further the stimulus for this effect, its specificity, and association with thirst, six volunteers were deprived of water for 24 h and given a salt load on two separate occasions. On each study day they then drank rapidly 10 ml/kg of either tap water or hypertonic saline (360 mosmol/kg). There was a significant fall in plasma AVP from 2.0 +/- 0.3 to 1.2 +/- 0.4 pmol/l (P less than 0.05) 5 min after drinking water and from 1.8 +/- 0.3 to 0.9 +/- 0.2 pmol/l (P less than 0.05) after hypertonic saline. Plasma osmolality fell 30-60 min after water and was unchanged after saline. Plasma renin activity, oxytocin, and total protein all remained unchanged. All subjects reported diminished thirst after hypertonic saline. Gargling with water reduced thirst but did not affect plasma AVP. There appears to be a drinking-mediated neuroendocrine reflex that decreases plasma AVP irrespective of the osmolality of the liquid consumed. The sensation of thirst did not correlate with plasma osmolality and was not always related to plasma AVP concentration.
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PMID:Oral hypertonic saline causes transient fall of vasopressin in humans. 374 Mar 1

Neurosecretory granules from the rat and bovine neurohypophysis were isolated and some of their biochemical and biophysical properties studied. Neurosecretory granules (NSG) from rat neurohypophysis were labeled, in vivo, with [35S]cysteine and isolated on isoosmotic gradients. Whereas 1 day after labeling most of the radioactivity was found in the lower part of the gradient, 35 days later the isotope was also located in the lighter NSG-containing fraction. Different analytical procedures showed that the lighter fraction, both in bovine and rat NSG, contain more subpopulations of neurophysin-like material than the heavier fraction. The first material to be released during stimulation of secretion, in vivo or in vitro, is mobilized from the heavy NSG. Isolation of rat NSG, at different times during and after dehydration of the animals, reveals that the newly synthesized material is found in the heavy NSG-containing fraction. Furthermore, the results indicate that the newly synthesized NSG are more resistant to lysis than the lighter granules. The results are discussed in relation to the maturation and degradation processes of the granule content and to the functional state of the NSG.
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PMID:Characterization of newly formed and aged granules in the neurohypophysis. 376 Aug 74

Melatonin injected in a single intraperitoneal dose of 100 micrograms/100 g b.w. to euhydrated rats resulted in a decrease of neurohypophysial oxytocin content but the hypothalamic oxytocin storage as well as the hypothalamo-neurohypophysial storage of vasopressin were not changed. Following 8 d of once-daily melatonin treatment the hypothalamic and neurohypophysial oxytocin and vasopressin content was decreased. It might be therefore suggested that melatonin increases the release of neurohypophysial hormones and/or decreases their synthesis. Melatonin did not significantly modify the neurohypophysial vasopressin depletion rate in animals deprived of water up to 8 days. No consistent effects of melatonin on the decrease of hypothalamo-neurohypophysial content of oxytocin were noted under conditions of dehydration and simultaneous administration of melatonin up to 8 d.
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PMID:The influence of melatonin on the content of vasopressin and oxytocin in the hypothalamus and neurohypophysis in euhydrated and dehydrated male rats. 377 20

Endogenous opioid peptides inhibit secretion of oxytocin during dehydration, hemorrhage and parturition and attenuate release of vasopressin by tail electroshock. Diverse agents were used to stimulate the hypothalamo-neurohypophysial system to investigate the hypothesis that if oxytocin (or vasopressin) release were inhibited by opioid peptides regardless of the stimulus, the site of opiate action may be in the final common pathway (i.e. the magnocellular neuron) or on pituicytes in the neural lobe. Using male Sprague-Dawley rats, we therefore investigated the effect of an opiate receptor antagonist, naloxone (5 mg/kg s.c.), on the plasma concentrations of oxytocin and vasopressin elevated by various pharmacologic stimuli, including histamine (10 mg/kg i.p.), nicotine (0.15 or 1.5 mg/kg i.p.), isoproterenol (30 or 120 micrograms/kg i.m.) and increased [NaCl] in cerebrospinal fluid (CSF; 10 microliter artificial CSF containing 1 M NaCl i.v.t.). Control animals received saline (0.85%) or artificial CSF (containing 0.16 M NaCl). Animals were decapitated 60 s (increases[NaCl] in CSF) or 10 min after the stimulus or vehicle. Vasopressin and oxytocin were extracted from plasma and quantified by RIA. The concentrations of oxytocin and vasopressin in plasma were elevated (p less than 0.05) by histamine, isoproterenol (30 and 120 micrograms/kg), increases[NaCl] in CSF, and nicotine at the higher (1.5 mg/kg) but not lower (0.15 mg/kg) dose. Naloxone increased further (p less than 0.05) the concentration of oxytocin in plasma after histamine, nicotine (0.15 and 1.5 mg/kg), isoproterenol (30 and 120 micrograms/kg) and increases[NaCl] in CSF. Naloxone also increased (p less than 0.05) oxytocin concentration in controls receiving CSF or saline.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Naloxone effects on plasma vasopressin and oxytocin concentrations elevated by histamine, nicotine, isoproterenol and an acute increase in [NaCl] in cerebrospinal fluid. 379 91

The regulation of both arginine vasopressin (AVP) and oxytocin secretion was studied during rapid and prolonged osmotic stimuli in normal adult volunteers. In five subjects given an intravenous infusion of 0.85 mol NaCl at 0.05 ml/kg per min over 2 h there was a significant (P less than 0.05) rise only in plasma AVP, with no significant change in plasma levels of oxytocin. In six further subjects 5 days of restriction to 500 ml fluid daily resulted in significant increases of both plasma and 24-h urinary AVP, whereas there was no change in corresponding oxytocin levels. During another 5-day period in which the same subjects were given an additional 200 mmol sodium as well as having their fluid intake restricted to 1000 ml daily, there were again significant rises in plasma and 24 h urinary AVP with no change in corresponding oxytocin levels. We conclude that, in man, AVP is selectively secreted in response to both dehydration and high sodium intake, whilst even after the stimulus of rapidly increasing plasma osmolality during intravenous infusion of hypertonic saline the rise in oxytocin is not statistically significant. It therefore appears unlikely that oxytocin has a significant role in the physiological control of fluid balance in man.
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PMID:Vasopressin and oxytocin responses to acute and chronic osmotic stimuli in man. 394 36

Endogenous pituitary secretion of vasopressin (AVP) and oxytocin (OT) was studied in rats with induced dilutional hyponatremia that was sustained for 2-5 days. Graded infusions of hypertonic saline produced progressive increases in plasma osmolality, but despite large relative increases in osmolality, AVP and OT secretion was not significantly stimulated until plasma [Na+] reached normal ranges. Regression analysis of plasma AVP and OT levels once secretion was stimulated showed no significant shift of the osmotic threshold for neurohypophyseal secretion of either hormone, as well as equivalent slopes of plasma AVP and OT increases per unit increases in plasma osmolality, in the hyponatremic rats relative to normonatremic controls. After a 20-25% decrease in plasma osmolality, total brain water content of hyponatremic rats increased only 3-6%, whereas larger decreases (11-17%) in total brain electrolytes were found. During subsequent hypertonic saline infusions in the hyponatremic rats total brain water content decreased linearly, resulting in brain dehydration below normal total brain water levels before stimulation of AVP and OT secretion occurred. The stability of the osmotic threshold for neurohypophyseal secretion, despite evidence of brain adaptation to chronic hypotonicity, argues that cell volume regulation via solute loss is not a likely cause of resetting of the osmostat. Additionally, brains of hyponatremic rats were found to manifest significantly greater susceptibility to dehydration after hypertonic saline infusions than brains of normonatremic controls, which may be a consequence of brain solute loss from adaptation to chronic hypotonicity.
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PMID:Osmotic regulation of plasma vasopressin and oxytocin after sustained hyponatremia. 395 53

Neurohypophyses from rats dehydrated and rehydrated for different periods of time have been analyzed by morphometry of electron micrographs and their oxytocin and vasopressin contents measured by radioimmunoassays. The time course of disappearance and reappearance of neurosecretory granules (NSG) parallels that of the hormone content of the neurohypophysis. Depletion of NSG during dehydration first occurs in the nerve endings and only later in the swellings. No change of the volumetric density of the microvesicles was detected but the time course of changes in the volumetric density of the endocytotic vacuoles varies according to the secretory state of the tissue. There was a significant increase in the volume of the gland 3 days after the beginning of the rehydration. This increase was associated with an increase in the volumetric density of the pituicytes. No change of the total number of endings, swellings and axons was observed. This demonstrates a hypertrophy of the pituicytes. The present work gives strong support to the concept of a preferential release of the granules located in the endings. It also shows that, after depletion of the NSG in the neural lobe, newly synthetized granules at the onset of rehydration move first to the endings and 2 days later arrive in the swellings coming presumably either directly from the hypothalamus or from the endings. Furthermore, the results confirm previous work which has demonstrated that membrane retrieval in neurohypophysial nerve endings occurs via vacuoles.
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PMID:Hormone content and movement of neurosecretory granules in the rat neural lobe during and after dehydration. 396 97

Biochemical, cytochemical and immunological methods were used to compare the metabolic and neuroendocrine properties of the subfornical organ (SFO) with the hypothalamo-neurohypophysial system (HNS) in the rat. The SFO resembles the HNS in that both have (a) increased label incorporation into RNA during dehydration; (b) an intense reaction for glucose-6-phosphate dehydrogenase; (c) NADPH-diaphorase and the Type I pathway for hydrogen utilization from NADPH, presumably as part of the mixed-function oxidase system for the metabolism of endogenous substrates and xenobiotics; (d) immunoreactive vasopressin and oxytocin. Gel filtration of extracts of the SFO area using Sephadex G-25 chromatography resulted in immunoreactive peaks for both AVP and OT which were similar to synthetic hormones. One other fraction in the SFO extract, containing a substance(s) of higher molecular weight than AVP, was detected using the antiserum for AVP. The concentration of immunoreactive AVP in the SFO area was increased after colchicine, decreased by hypophysectomy, and unaltered by: (a) infusion (4.6 pg/min for 3 hr) or injection (1 or 6 ng) of AVP into the lateral cerebroventricle; (b) dehydration; (c) renin administered intracerebroventricularly; (d) pinealectomy; or (e) hypertension in the spontaneously hypertensive rat. In conclusion, cells in the SFO have specialized metabolic and neuroendocrine properties similar to the HNS. It can be inferred from these biochemical specializations that the SFO has metabolic and secretory activities.
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PMID:The subfornical organ: biochemical and neuroendocrine comparisons with the hypothalamo-neurohypophysial system. 402 8


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