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Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Peripheral administration of vasopressin (VP) was previously shown to exert a negative feedback influence on its own release and on the release of oxytocin (OT). In this study we examined the possible influence that OT has on the function of hypothalamic magnocellular neurones. Oxytocin was administered intraperitoneally and its effects on release from VP neurones and from OT neurones were determined as indexed by plasma concentrations of vasopressin-associated neurophysin ([VP-RNP]) and oxytocin-associated neurophysin ([OT-RNP]) under basal conditions and conditions of high plasma osmolality (Posm) induced by acute salt loading. Studies were performed on conscious, chronically instrumented Long-Evans rats. Oxytocin (1 nmol or 10 nmol) dissolved in 1 mL of 0.9% saline was administered intraperitoneally to animals 1 h before they received an intravenous infusion of hypertonic saline over 60 min at a rate designed to raise Posm by approximately 0.75 mosmol.min-1. Intraperitoneal injection of vehicle or 1 nmol of OT did not significantly alter [VP-RNP], [OT-RNP], or basal Posm. Administration of 10 nmol OT also had no effect on [VP-RNP] or [OT-RNP], but this dose of peptide significantly lowered basal Posm (299 +/- 2 to 290 +/- 2 mosmol/kg H2O, p less than 0.001). Both doses of OT did not significantly alter the responsiveness of VP neurones to hyperosmotic stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Absence of negative feedback by oxytocin on release from magnocellular neurones in conscious rats. 158 42

We investigated the ontogeny of provasopressin gene expression in neurosecretory neurons of the supraoptic and paraventricular nuclei of developing mice by semi-quantitative in situ hybridization and immunohistochemical techniques in combination with stereometry of vasopressin-immunoreactive neurons. Provasopressin mRNA was detected in paraffin sections using a mixture of radiolabeled synthetic oligonucleotide probes complementary to the mRNA loci encoding vasopressin (2-9) and vasopressin neurophysin (1-8). Vasopressin immunoreactivity was located with a polyclonal anti-vasopressin antiserum and a monoclonal anti-vasopressin-neurophysin antibody either with or without enhancing technique for the diaminobenzidine reaction. Autoradiographic hybridization signals that indicate the localization of provasopressin mRNA were first detected on embryonic day 15 in the supraoptic nucleus and embryonic day 18 in the paraventricular nucleus. Vasopressin immunoreactivity was first found in the median eminence on embryonic day 14, and then in the supraoptic and paraventricular nuclei on embryonic days 15 and 16, respectively. The provasopressin mRNA levels were markedly increased in both the supraoptic and the paraventricular nuclei just after birth. The immunoreactivity of vasopressin neurons was drastically decreased in both nuclei on postnatal days 1 and 2, suggesting marked vasopressin release in the neonates. Cross-sectional areas of vasopressin-immunoreactive somata and their cell nuclei gradually increased in both the supraoptic and the paraventricular nuclei during the perinatal period by day 5, and then attained adult size between days 10 and 20. During this phase, the level of provasopressin mRNA remained low compared with that in the adult magnocellular neurosecretory cells. These results indicate that the expression of provasopressin gene is markedly increased in both the supraoptic and the paraventricular nuclei soon after birth. Secretory activity of vasopressin neurons is elevated in neonatal mice. Vasopressin may have an important osmoregulatory role in neonatal mice undergoing drastic changes in water metabolism following birth.
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PMID:Expression of provasopressin gene during ontogeny in the hypothalamus of developing mice. 159 5

Teat and gland cistern of the mammary glands of five dairy cows, five goats and five sheep were scanned in a water bath during alpha- and beta-adrenergic agonist and oxytocin administration. A 5 MHz linear array scanner was used to create vertical cut pictures with the scan plane longitudinally through the teat channel. The i.v. injection of the alpha-adrenergic agonist phenylephrine (30 micrograms/kg) induced diminution of the section area through teat and gland cistern by 38 +/- 17% on average within 1 min in all three species. In contrast, the i.v. injection of the beta-adrenergic agonist isoproterenol (1 microgram/kg) did not change the cisternal areas. The i.v. injection of oxytocin (2.0 x 10(-3) i.u./kg) elicited an enlargement of teat and gland cistern area by 48 +/- 12% on average. Ultrasonography proved to be a valuable system for visualizing changes of the cisternal volume. Smooth muscle contractions in response to phenylephrine administration are thought to cause area reduction, whereas an expected smooth muscle relaxation after injection of isoproterenol could not be observed by ultrasonography. Milk ejection as induced by oxytocin administration caused dramatic enlargement of the cistern area in all three species.
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PMID:B-mode ultrasonography of mammary glands of cows, goats and sheep during alpha- and beta-adrenergic agonist and oxytocin administration. 161 73

Patterns of neurohypophysial hormone secretion and changes in the hormone content of the hypothalamus and posterior pituitary lobe were monitored in the male rat for cycles of 24 h in association with changes in food and water intake and fluid excretion. Plasma oxytocin and vasopressin concentrations were seen to rise significantly over the hours of daylight, decreasing during the night. Parallel changes were seen in the immunoreactive material in the hypothalamus, whilst the content of the neurohypophysis was inversely related to plasma concentrations. The ratio of plasma oxytocin:vasopressin reached a significant peak at about 02.00 h which might be related to the feeding activity of the rats, food and water intake being largely confined to the night, as was fluid excretion. On exposure to constant light, despite initial disruption hormonal rhythms were still seen but showed a phase shift. The relationships between plasma and tissue levels were maintained. Patterns of food and water intake and urinary excretion were little affected by exposure to constant light, remaining largely confined to the former night phase. The hormonal rhythms appeared to be more closely related to the activity of the rats, which also showed a phase shift during constant light.
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PMID:Daily rhythms in the hormone content of the neurohypophysial system and release of oxytocin and vasopressin in the male rat: effect of constant light. 161 30

It has been shown that during physiological stimuli, such as dehydration, supraoptic nucleus (SON) neurons undergo profound morphological changes. However, little is known about how much each type of cell, oxytocin (OT) or vasopressin (VP), contributes to this plasticity during dehydration. Using postembedding immunogold cytochemistry for both OT and VP hormones at the electron microscopic level, we address this question. Rats were chronically dehydrated (given 2% saline to drink for 10 days) and their SON neurons were studied morphologically. The results were compared to control animals with free access to water. Both VP and OT somata showed an enlargement in size in dehydrated animals. Percentage of somasomatic/dendritic membrane contact increased significantly in both VP and OT neurons, with no significant changes in percentage of coverage of the cells by astrocytic membrane. Only the VP cells had a lesser amount of axosomatic membrane contact after dehydration, possibly due to an increase in cell size rather than a decrease in synaptic contact. Multiple synapses (MSs) (i.e., terminals that form more than one synapse with adjacent somata and or dendrites) occurred only between positively labeled cells and between negatively labeled cells, but not between positively and negatively labeled cells. The number of MSs per 100 microns OT somatic membrane or per 100 OT cells was significantly higher in dehydrated rats but was unchanged with regard to VP neurons. These findings indicate that both VP and OT neurons undergo morphological changes during chronic dehydration and, thus, that plasticity is not limited to OT cells as some earlier reports have suggested.
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PMID:Reevaluation of the plasticity in the rat supraoptic nucleus after chronic dehydration using immunogold for oxytocin and vasopressin at the ultrastructural level. 161 60

Intracerebroventricular administration of oxytocin (OT) and an OT agonist significantly decreased food intake in a dose-related manner in fasted rats. Central administration of an OT antagonist by itself (up to doses of 8 nmol) did not potentiate deprivation-induced food intake, but pretreatment with the OT receptor antagonist prevented the expected inhibition of food intake produced by OT and the OT agonist. Once-daily ICV injections of OT led to the development of tolerance to the inhibitory effects on food intake by the third day of treatment, but daily pretreatment with the OT antagonist prevented the development of this tolerance. In addition to causing decreased food intake, ICV administration of OT significantly increased grooming behavior but produced no dyskinesias. The inhibitory effect of OT on food intake was characterized by decreased amounts of food intake but a normal pattern of ingestion. The anorexia produced was central in nature and was not associated with altered plasma levels of hormones involved in caloric homeostasis or with changes in blood glucose. The OT agonist had relatively little effect on water intake when given in doses that significantly inhibited food intake. These results support the hypothesis that specific OT receptors within the central nervous system participate in the inhibition of feeding under certain conditions in rats.
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PMID:Oxytocin and an oxytocin agonist administered centrally decrease food intake in rats. 164 95

We have compared the response of proton and water transport to oxytocin treatment in isolated frog skin and urinary bladder epithelia to provide further insights into the nature of water flow and H+ flux across individual apical and basolateral cell membranes. In isolated spontaneous sodium-transporting frog skin epithelia, lowering the pH of the apical solution from 7.4 to 6.4, 5.5, or 4.5 produced a fall in pHi in principal cells which was completely blocked by amiloride (50 microM), indicating that apical Na+ channels are permeable to protons. When sodium transport was blocked by amiloride, the H+ permeability of the apical membranes of principal cells was negligible but increased dramatically after treatment with antidiuretic hormone (ADH). In the latter condition, lowering the pH of the apical solution caused a voltage-dependent intracellular acidification, accompanied by membrane depolarization, and an increase in membrane conductance and transepithelial current. These effects were inhibited by adding Hg2+ (100 microM) or dicyclohexylcarbodiimide (DCCD, 10(-5) M) to the apical bath. Net titratable H+ flux across frog skin was increased from 30 +/- 8 to 115 +/- 18 neq.h-1.cm-2 (n = 8) after oxytocin treatment (at apical pH 5.5 and serosal pH 7.4) and was completely inhibited by DCCD (10(-5) M). The basolateral membranes of the principal cells in frog skin epithelium were found to be spontaneously permeable to H+ and passive electrogenic H+ transport across this membrane was not affected by oxytocin. Lowering the pH of the basolateral bathing solution (pHb) produced an intracellular acidification and membrane depolarization (and an increase in conductance when the normal dominant K+ conductance of this membrane was abolished by Ba2+ 1 mM). These effects of low pHb were blocked by micromolar concentrations of heavy metals (Zn2+, Ni2+, Co2+, Cd2+, and Hg2+). Lowering pHb in the presence of oxytocin (50 mU/ml) produced a transepithelial current (3 microA.cm-2 at pHb 5.5) which was blocked by 100 microM of Hg2+, Zn2+, or Ni2+ at the basolateral side, and by DCCD (10(-5) M) or Hg2+ (100 microM) from the apical side. The net hydroosmotic water flux (JH2O) induced by oxytocin in frog bladder sacs was blocked by inhibitors of H(+)-adenosine triphosphatase (ATPase). Diethylstilbestrol (DES 10(-5) M), oligomycin (10(-8) M), and DCCD (10(-5) M) prevented JH2O when present in the lumen. These effects cannot be attributed to inhibition of metabolism since cyanide (10(-4) M), or 2-deoxyglucose (10(-3) M) had no effect on JH2O.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Common channels for water and protons at apical and basolateral cell membranes of frog skin and urinary bladder epithelia. Effects of oxytocin, heavy metals, and inhibitors of H(+)-adenosine triphosphatase. 164 38

We have investigated the effects of stress on the plasma levels of adrenocorticotropin (ACTH), corticosterone and oxytocin (OT) in rats given 2% saline to drink for 12 days. Plasma ACTH levels were markedly decreased from 972 +/- 165 pg/ml in the control animals on water to 349 +/- 114 pg/ml in animals given 2% saline to drink. Stress-induced release of ACTH observed in animals on water (controls = 972 +/- 165 pg/ml and stressed animals = 1,439 +/- 105 pg/ml) was completely abolished following 2% saline treatment for 12 days (controls = 349 +/- 114 pg/ml and stressed animals = 205 +/- 27 pg/ml). After 2% saline, plasma corticosterone levels were unaltered in control and stressed animals as compared to control animals on water in which stress increased plasma corticosterone from 28.8 +/- 7.9 to 99.5 +/- 8 ng/ml. In contrast to ACTH, the OT response to stress was intact in animals on 2% saline despite raised plasma OT in the control group due to the osmotic stimulus. Removal of the source of circulating glucocorticoids by adrenalectomy partially restored both basal levels of ACTH and the response to stress in animals on 2% saline. Our results demonstrate that 2% saline treatment activates an inhibitory mechanism over the release of ACTH.
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PMID:Altered adrenocorticotropin, corticosterone and oxytocin responses to stress during chronic salt load. 166 2

The effects of highly selective agonists and antagonists to the mu-, delta- and kappa-opioid receptor subtypes were studied on the vasopressin and oxytocin release in 24 h water-deprived male rats. The delta-agonist [D-Pen2,D-Pen5]enkephalin (dose range 0.01-5 mg/kg) did not affect plasma levels of either hormone 30 min after s.c. administration, whereas the mu-agonist DALDA (H-Tyr-D-Arg-Phe-Lys-NH2) over the same dose range strongly inhibited the release of both vasopressin and oxytocin, an effect that was maximal 30-60 min after s.c. injection. The same effect was found for s.c. administration of the kappa-agonist U-69,593. Intracerebroventricular (i.c.v.) administration of DALDA (0.5 and 5 micrograms/kg) but not U-69,593 suppressed both plasma hormone levels 30 min after injection. Also the effects of selective antagonists were tested over the s.c. dose range of 0.01-1 mg/kg. Whereas both the kappa-selective antagonist nor-binaltorphimine and the relatively mu-selective antagonist naloxone elevated oxytocin plasma levels (peak at 15 and 30 min after injection, respectively), the delta-selective antagonist naltrindole was without any effect. Nor-binaltorphimine, naloxone, and naltrindole did not affect vasopressin release. When the antagonists were administered i.c.v. (dose range 2.5-25 micrograms/kg), only the kappa-antagonist nor-binaltorphimine enhanced oxytocin and vasopressin release 30 min after injection. In conclusion, both mu- and kappa-opioid receptors are involved in the regulation of the secretion of vasopressin and oxytocin from the rat neural lobe; in contrast, delta-opioid receptors do not play a role.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The opioid receptor subtypes mu and kappa, but not delta, are involved in the control of the vasopressin and oxytocin release in the rat. 166 95

The time course of acute changes in vasopressin (VP) and oxytocin (OT) mRNA size and level during dehydration has been studied in rats. Total RNA was extracted from samples of the supraoptic nucleus at various intervals after water deprivation, subjected to northern blotting, and probed with oligonucleotides specific for VP and OT mRNA. The VP and OT mRNA size, shown previously to reflect 3'-poly (A) tail length, was consistently increased 2 h after dehydration, prior to significant changes in plasma osmolality or haematocrit. Intraperitoneal administration of hypertonic saline resulted in a similarly rapid VP and OT mRNA size response, in some cases within 1 h of treatment. The effect of a discrete hypovolaemic stimulus was investigated with intraperitoneal injections of polyethylene glycol; again, the VP and OT mRNA size was rapidly increased. No significant changes in mRNA level were observed in any of the experimental groups. The results show that an increase in VP and OT mRNA poly(A) tail length forms an acute and general response to activation of the hypothalamo-neurohypophyseal system. The rapidity of the poly (A) tail response, which appears to be independent of physiological signalling mechanisms associated with increases in mRNA accumulation (observed after 2 days of dehydration), provides a paradigm for the investigation of novel modes of neuronal gene regulation.
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PMID:Rapid changes in poly (A) tail length of vasopressin and oxytocin mRNAs form a common early component of neurohypophyseal peptide gene activation following physiological stimulation. 167 37


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