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

Morphological and pharmacological evidence suggest that the dense GABAergic innervation of the supraoptic nucleus is important for regulating the electrical activity of vasopressin and oxytocin neurons. We have employed the technique of intracranial microdialysis to examine extracellular GABA concentrations in the supraoptic nucleus of the anaesthetized rat and questioned whether differences exist in the dynamics of GABA release between virgin and lactating rats, and if events during lactation or following blood pressure manipulation alter endogenous GABA levels in this nucleus. No significant differences were detected between virgin and lactating animals in either basal or 100 mM potassium ion-evoked GABA release. The inclusion of the GABA uptake blocker nipecotic acid (0.5 mM) into the dialysate resulted in a six- to eight-fold increase (P < 0.01) in GABA outflow in both groups of animals. In lactating rats, GABA outflow measured at 4 min intervals was not altered during a 60 min period of suckling by a full litter of pups and no significant change in GABA outflow was detected in relation to individual milk ejections. In virgin rats, removal of 1.5-2 ml of blood resulted in a 30-60 mmHg fall in blood pressure and a non-significant decline in GABA outflow. Replacement of blood resulted in an abrupt 50 mmHg increase in blood pressure and a significant 22% increase in GABA outflow (P < 0.01), but no change in aspartate or methionine concentrations. Repeated intravenous injections of the alpha-adrenoceptor agonist, metaraminol, similarly evoked approximately 50 mmHg increments in blood pressure and a 26% increase in GABA outflow (P < 0.05). Electrical stimulation of the diagonal band of Broca for 10 min produced a two-fold increase in GABA outflow from the supraoptic nucleus (P < 0.05). These results show that the overall profile of basal and potassium-stimulated GABA concentrations in the supraoptic nucleus is not substantially different between lactating and virgin rats. In lactating animals we have found that GABA levels are not altered in response to suckling or at the time of high-frequency firing by oxytocin neurons to induce milk ejection. In contrast, our data further support the hypothesis that GABA inputs to supraoptic neurons are part of a baroreceptor reflex, relaying through the diagonal band of Broca, to signal periods of acute hypertension and inhibit the firing of vasopressin neurons. Such observations suggest the physiological importance of GABA inputs to the supraoptic nuclei and indicate that GABA may be used in a stimulus-specific manner to influence the activity of magnocellular neurons.
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PMID:Extracellular GABA concentrations in rat supraoptic nucleus during lactation and following haemodynamic changes: an in vivo microdialysis study. 789 64

Embryonic hypothalamic tissue originating from spontaneously hypertensive rats (SHR) was implanted in young normotensive Wistar Kyoto rats in an attempt to localize hypothalamic regions directly responsible for the induction of hypertension. A 25% increase in host systolic blood pressure as compared with the controls was recorded 3 months after implantation in the animals receiving rostral hypothalamic tissue (R-SHR), whereas blood pressure was not affected in the animals grafted with caudal hypothalamic tissue (C-SHR). The hypertension in the R-SHR group was accompanied by hypertrophy of the heart and kidneys. The number of vasopressin-immunopositive (VPi) parvocellular cells in the hypothalamic paraventricular nucleus (PVN) of the R-SHR group was massively reduced (by 72%), while that of the tyrosine hydroxylase-immunopositive cells displayed no change. In the suprachiasmatic nucleus of these animals the VPi cell number was unaltered. In the C-SHR, the amount of parvocellular VPi cells was also unaltered. Likewise, oxytocin-containing cells were the same in all groups. DNA nick-end labeling of the tissue revealed that PVN cells are undergoing programmed cell death. These results implicate a selective degeneration by hypothalamic PVN cells in the pathogenesis of hypertension.
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PMID:Selective elimination of hypothalamic neurons by grafted hypertension-inducing neural tissue. 791 56

Serial measurements of plasma oxytocin concentration were done by radioimmunoassay in 38 cases of pregnancy induced hypertension (PIH) and 38 cases of normal pregnancy (NP). The results showed that there was no obvious difference in the plasma oxytocin concentration between patients with early PIH and NP, but a higher concentration in cases with PIH at term pregnancy than that in NP and a significantly higher level in intrapartum women with PIH. The results also indicated a much higher oxytocin concentration in cases of moderate and severe PIH as compared to that of NP. An obviously higher level of plasma oxytocin was found in severe PIH than in mild PIH. Based on this study we suggest that the clinical use of oxytocin in cases with PIH should be different from that in NP.
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PMID:[Changes in blood oxytocin levels in cases of pregnancy induced hypertension]. 795 47

To study the oxytocic effect of trypsin, we measured the force of isometric contraction in uteri isolated from estrogenized rats exposed to trypsin (8.8 x 10(-10) to 1.7 x 10(-6) mol/L) either alone or in the presence of receptor antagonists to angiotensin II [saralasin ([Sar1,Ala8]angiotensin II) or DuP 753 (losartan)] or to kinins (D-[Arg0,Hyp3,Thi5,8,D-Phe7]-bradykinin). We found that saralasin or DuP 753, but not the kinin antagonist, displaced the dose-response curve to the right. Exposure to exogenous angiotensin I desensitized the preparation to further doses of either angiotensin I or II or trypsin, without altering the effects of oxytocin or bradykinin. Enalaprilat (an angiotensin I converting enzyme inhibitor) or pepstatin A (a renin inhibitor) also displaced the dose-response curve to trypsin to the right, without altering the effects of oxytocin or angiotensin II. Our results indicate that the response to trypsin is mediated by an agent produced from a substrate present in the uterus and acting on the angiotensin II type 1 receptor and are consistent with both renin and angiotensin I converting enzyme being involved in its mechanism of action, thus supporting the notions that the renin-angiotensin system may be important in the late stages of pregnancy and that serine proteases existing in the uterus may contribute to its activation.
Hypertension 1994 Jan
PMID:Oxytocic effect of trypsin on the isolated rat uterus. 828 69

Mesenteric artery rings from Wistar and Wistar-Furth rats subcutaneously treated with deoxycorticosterone acetate (DOCA) and 1% NaCl drinking water were used to measure endothelial modulation of contractile sensitivity and vasopressin receptor function and affinity. DOCA-salt hypertension reduced contractile sensitivity to arginine vasopressin (AVP) and did not affect contractile sensitivity to norepinephrine in arteries from Wistar rats. Endothelial removal caused a threefold increase in contractile sensitivity to AVP and norepinephrine in DOCA-salt hypertensive Wistar rats. In Wistar-Furth rats, DOCA-salt treatment did not affect contractile sensitivity to AVP, lysine vasopressin, oxytocin, and norepinephrine or the affinity of the vasopressin receptor for agonists or antagonists. Removal of endothelium did not affect vasopressin contractile sensitivity but caused a 15-fold increase in contractile sensitivity to norepinephrine in untreated or DOCA-salt-treated Wistar-Furth rats. These data show that reduced vasopressin receptor function and increased endothelial function that compensate for increased contractile sensitivity in arteries from DOCA-salt hypertensive Wistar rats are not the cause of resistance of DOCA-salt-treated Wistar-Furth rats to the development of enhanced contractile sensitivity and hypertension.
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PMID:Endothelium, vasopressin receptors, and resistance to DOCA-salt hypertension. 834 27

There is considerable evidence that the central nervous system (CNS) is significantly involved in potassium homeostasis: (a) Potassium-specific receptors located in the liver or hepatic portal circulation initiate a reflex increase in potassium excretion via vagal afferents. This reflex is lost or diminished with hypophysectomy. (b) Oscillators, presumably located in the hypothalamus, determine a circadian rhythm in the renal excretion of potassium. The efferent control factors are unknown. (c) Exogenous hypophysial peptides (vasopressin, oxytocin, and alpha-, beta-, and gamma-MSH) stimulate increased potassium (and sodium) excretion. (d) Hypophysial gamma-MSH or a related hypophysial peptide stimulates an increase in the excretion of potassium (and sodium) following uninephrectomy in the rat. This adaptive response involves cerebral, naloxone-inhibitable opioid receptors. (e) Intra-third-ventricular infusion of hypertonic NaCl initiates an increased potassium (and sodium) excretion through undetermined humoral mechanisms and is blocked by prior hypophysectomy. (f) In rats depleted of potassium by low potassium intake or by production of DOCA hypertension, an inhibition of skeletal muscle Na+, K(+)-ATPase ion pump activity is directed by hypothalamic centers and involves inhibition by alpha-adrenergic activity of slow twitch fibers and inhibition by undetermined humoral factors of fast twitch fibers. (g) Potassium receptors, either demonstrated or inferred, initiate reflex increases in respiration, heart rate, blood pressure, and peripheral tissue potassium uptake as well as a reflex inhibition of skeletal muscle ion pumps. (h) Evidence for CNS regulation of potassium intake is equivocal. Major gaps exist in this emerging picture of neuroendocrine involvement in potassium homeostasis.
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PMID:The central nervous system in potassium homeostasis. 847 70

The authors review various aspects of gestational diabetes, including definition, screening, diagnostic procedures, complications (hypertension, macrosomia), clinical evaluation (ultrasound, non-stress test), treatment (diet, insulin), indications for delivery and neonatal aspects (hypoglycaemia, hypocalcaemia). Complications can be reduced by intensive dietary treatment and insulin. If the gestational diabetes is regulated well the woman can wait for spontaneous birth at term. In the case of pregnant women with less than optimal regulated diabetes, however, or with complications such as hypertension, macrosomia, previous stillbirth, labour can be induced preterm by local administration of prostaglandin or infusion of oxytocin. Physical training and weight reduction should be instituted to avoid later development of type II diabetes mellitus. There is still some uncertainty about different aspects of gestational diabetes.
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PMID:[Pregnancy in diabetes]. 926 87

The overall rate of induction of labor in the United States in 1993 was 134 per 1,000 live births, or over 527,000 of the four million births that occur annually in the United States. Indications for labor induction include postdate pregnancy, premature rupture of membranes (PROM), and maternal medical complications, such as diabetes mellitus and pregnancy-induced hypertension. This article briefly reviews common indications for induction of labor and the importance of cervical ripening. It then addresses methods used to hasten cervical ripening and to induce labor, ranging from the more "natural" and noninvasive methods, such as nipple stimulation, to the newest commercially available formulation of prostaglandin. Methods well documented in the scientific literature, as well as those commonly used but less well studied, are included. Although one may argue about the "invasive" nature of these methods, they are addressed, in general, from the most natural methods to the latest pharmacologic methods, and they include the following: sexual intercourse, nipple/breast stimulation, herbal preparations, homeopathic solutions, castor oil, enemas, acupuncture, membrane sweeping or stripping, mechanical dilation (balloon catheters, laminaria, and synthetic osmotic dilators), amniotomy, and pharmacologic hormonal preparations (prostaglandin E2, oxytocin, misoprostol, mifepristone, and relaxin).
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PMID:Methods of cervical ripening and labor induction. 910 14

The safety and effectiveness of 25 and 50 mcg of intravaginally administered misoprostol for cervical ripening and labor induction were evaluated in a randomized double-blind trial involving 395 US women. The most frequent indications for labor induction in both dosage groups were pregnancy-induced hypertension and premature rupture of the membranes. The prostaglandin dosage was repeated every 3 hours until labor was induced. The mean start-to-delivery interval among the 192 women in the 25 mcg group was 970 minutes, compared to only 826 minutes among the 207 women in the 50 mcg group. 82% of women in the 25 mcg group and 84% of those in the 50 mcg group were delivered within 24 hours. The incidence of vaginal delivery after 1 dose was higher in the 50 mcg group (38.2%) than in the 25 mcg group (25.0%) and women in the lower-dose group required oxytocin administration more frequently than those in the 50 mcg group (27.1% and 16.9%, respectively). On the other hand, the incidence of newborns with a cord pH under 7.16 was greater in the 50 mcg group (13.0%) than in the 25 mcg group (6.8%), and the incidence of tachysystole was higher (32.8% and 15.6%, respectively). Thus, despite the greater effectiveness of the 50 mcg dosage, a regimen of 25 mcg of misoprostol administered intravaginally every 3 hours is indicated to minimize neonatal morbidity.
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PMID:Randomized trial of two doses of the prostaglandin E1 analog misoprostol for labor induction. 929 Apr 52

Stimulation of brain periventricular and hypothalamic substance P receptors induces a pressor response and tachycardia associated with mesenteric and renal vasoconstriction and hindlimb vasodilation resembling thus the classical defense reaction. This cardiovascular response is brought about by the activation of the sympathoadrenal system and is accompanied by grooming behavior. To address the role of oxytocinergic pathways in the brain in the mediation of these responses, we investigated the effects of central pretreatment of rats with oxytocin antisense, mixed base, and sense oligodeoxynucleotides on mean arterial pressure, heart rate, and grooming behavior induced by intracerebroventricular injections of substance P (50 pmol). Central pretreatment of conscious rats with the oxytocin antisense oligodeoxynucleotide (intracerebroventricular injections, 8 and 4 hours before administration of substance P) attenuated the mean arterial pressure (by 55%) and heart rate responses (by 58%) as well as grooming behavior induced by the peptide. A complete recovery of all substance P-induced responses was observed 28 hours after antisense oligodeoxynucleotide pretreatment. Intracerebroventricular pretreatment of rats with mixed base and sense oligodeoxynucleotides did not affect the cardiovascular and behavioral responses to substance P. The signal for oxytocin mRNA in the paraventricular nucleus was reduced only in rats pretreated with the antisense oligodeoxynucleotide. These results demonstrate that oxytocin neurons in the paraventricular nucleus, which innervate the cardiovascular centers in the hindbrain and the spinal cord, mediate the increases in blood pressure and heart rate induced by stimulation of substance P receptors in the forebrain. These neurons may also transmit signals, which are generated by substance P in the hypothalamus and are responsible for the sympathoadrenal activation in response to stress.
Hypertension 1998 Jan
PMID:Oxytocin pathways mediate the cardiovascular and behavioral responses to substance P in the rat brain. 945 49


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