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)

An investigation was undertaken to determine if the incidence of third- and fourth-degree perineal tears has changed and, if so, what the predisposing factors might be. Data were analyzed for a 50-year period (1935-1985). An increased frequency of such tears was found after 1965, when mediolateral episiotomies were replaced almost entirely by midline ones. A constant combined rate of 17% for third- and fourth-degree tears was found for the last decade. When compared with a similar group without such tears, women with extensive tears were more likely to be nulliparous and teenage and to require epidural anesthesia, oxytocin and/or forceps application. When the incidence of tears was compared with that at a nearby community hospital, it was found to be higher at our university medical center. Excluding physician inexperience, the reason was the greater frequency of teenage pregnancies and more common use of epidural anesthesia and oxytocin at our hospital. Rectovaginal fistulae and anal incontinence requiring repair occurred in less than 1% of the total cases. Since midline episiotomies are now being performed often, third- and fourth-degree perineal tears will continue to be common and will depend on the patient population, physician experience and intrapartum hospital policies.
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PMID:Third- and fourth-degree perineal tears. 50 year's experience at a university hospital. 338 96

We have investigated the secretion of oxytocin and arginine vasopressin (AVP) during vaginocervical stimulation in the conscious goat and examined the effect of the opioid antagonist naloxone on peptide release to this stimulus. Goats were implanted with guide tubes overlying the cisterna magna under anaesthesia and allowed to recover. Vaginocervical stimulation for 60 s resulted in a marked (P less than 0.01) release of oxytocin into the plasma but neither plasma AVP nor cerebrospinal fluid (CSF) concentrations of oxytocin changed significantly. In a second series of experiments, unoperated goats were infused with saline or naloxone (4 mg bolus + 12 mg/h) in random order on two separate occasions. Infusion of naloxone had no effect on basal plasma concentrations of oxytocin or AVP. There was a marked and significant (P less than 0.01) potentiation of oxytocin secretion following vaginocervical stimulation in animals infused with naloxone. Naloxone-infused animals showed a significant (P less than 0.01) rise in plasma AVP after stimulation but plasma AVP did not change in the saline-infused controls. We conclude that vaginocervical stimulation leads to the selective release of oxytocin from the neurohypophysis without affecting concentrations of oxytocin in the CSF. Endogenous opioids inhibit the stimulated secretion of oxytocin and AVP in vivo in response to vaginocervical stimulation in the goat.
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PMID:Effect of naloxone on oxytocin and vasopressin release during vaginocervical stimulation in the goat. 343 51

Intermittent and continuous electrical stimulation of the nipples elicited milk-ejection responses in the lactating rat. The responses occurred intermittently, with similar amplitudes and periodicity as those seen in suckled rats. The responses were always associated with synchronization of the electroencephalogram (EEG), but some rats with synchronized EEG activity did not milk eject during stimulation. Since continuous stimulation also resulted in intermittent milk ejection it seems unlikely that the periodicity of the reflex in suckled rats depends upon changes in the intensity of sensory stimulation. The techniques of nipple stimulation may be a useful method with which to study neural pathways and other phenomena such as gating involved in oxytocin release and milk ejection. The success of the technique depends on a variety of factors such as parameters of the stimulation and state of anaesthesia.
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PMID:Prolonged electrical stimulation of the nipples evokes intermittent milk ejection in the anaesthetised lactating rat. 358 33

One physiological role for endogenous opioid peptides is to attenuate the release of oxytocin (OT) from the hypothalamo-neurohypophysial system during dehydration and hemorrhage when vasopressin maintains fluid balance and blood pressure. During lactation, OT, which stimulates milk ejection, is released without vasopressin. The influence of endogenous opioid peptides on OT release during suckling has been studied primarily in animals anesthetized with urethane. In addition to anesthesia, urethane dehydrates the animal by elevating plasma osmolality and reducing cardiovascular volume. Thus, we examined in lactating rats the response of the magnocellular neuroendocrine system to dehydration and the role of endogenous opioid peptides in regulating OT release during suckling under conditions of altered fluid balance in conscious and urethane-anesthetized rats. Release of OT in response to an increase in plasma osmolality or a decrease in blood volume was attenuated during lactation in both conscious and anesthetized rats. Blockade of opiate receptors with naloxone (5 mg/kg) did not alter suckling-induced release of immunoreactive OT in conscious, normally hydrated rats, but did augment hormone release after urethane (1.1 g/kg, ip) or after osmotic stimulation with hypertonic sodium chloride (2.5%; 20 ml/kg, ip). During dehydration, the combination of decreased responsiveness of oxytocinergic neurons to osmotic stimulation and inhibition of OT release by opioid peptides may be important in the lactating rat for conserving pituitary stores of OT needed for milk ejection.
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PMID:Endogenous opioid peptides inhibit oxytocin release in the lactating rat after dehydration and urethane. 359 30

Extracellular recordings were made from neurones in or near the supraoptic nucleus in suckled lactating rats under urethane anaesthesia to investigate the mechanism by which the firing of oxytocin cells is synchronized during reflex milk ejection. Cells synaptically driven but not antidromically activated by neural stalk stimulation, which thus probably receive an afferent input from supraoptic neurones, were classified as 'regular' or 'bursters' on the basis of their spontaneous electrical activity. The majority (twelve out of eighteen) of synaptically excited cells (o.d.+) were bursters and the majority of inhibited (o.d.-) cells (eleven out of nineteen) were regular, but only one o.d.+ burster showed any change of activity (inhibition) before milk ejection. Putative oxytocin cells in suckled lactating rats showed a firing pattern between milk-ejection bursts which could not be distinguished from that of putative oxytocin cells in male animals. The mode interspike interval between milk ejections was 47.1 +/- 3.1 ms (mean +/- S.E. of mean) compared with 47.3 +/- 3.3 ms in male rats, and fewer than 1.4% of interspike intervals were less than 20 ms in duration. By contrast, within milk-ejection bursts 40% of interspike intervals were in the range 8-20 ms. Short trains (10 or 20) of pulses applied to the neural stalk at regular (5 min) intervals, in an attempt to simulate the initial part of the milk ejection burst, failed to trigger bursts. In only 2 of 150 tests was the interval between train and milk-ejection burst less than 10 s, and after the pulse train all but one cell showed reduced activity for 1-3 s. The trains of pulses were however not without effect: they significantly (P less than 0.01) enhanced the chance of a milk-ejection burst occurring within the next 2.5 min. Our observation that pulse trains do not trigger bursts suggests that local positive feed-back mechanisms are not responsible for orchestrating the activation of oxytocin cells during the milk-ejection reflex. Moreover, because spontaneous tiring pattern is the same in lactating and non-lactating rats, we found no evidence that the anatomical changes in the synaptic organization within the supraoptic nuclei in lactation have any influence on the firing of oxytocin cells. It is likely, however, since pulse trains alter the timing of milk ejections, that oxytocin released locally in the region of the supraoptic nucleus can influence reflex milk ejection.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Regulation of the milk ejection reflex in the rat. 361 64

At 8 and 13 days post partum, rats have the same total milk availability; yet, in response to suckling they release a greater amount of milk on day 13 than on day 8. Increased sensitivity to suckling in the more advanced lactators may result from a greater release of oxytocin or from changes in the mammary glands as lactation advances. The present study explores this latter possibility in anaesthetized dams at 8-9 and 13-15 days of lactation. Milk release and intramammary pressure were measured in anaesthetized dams in response to various doses of oxytoxin. Milk release was determined from the body weight gain of pups which had been fasted for 5 h before suckling on dams which had been isolated for 5 h. This parameter was significantly greater in 13- to 15-day lactators than in 8- to 9-day lactators over the range of oxytocin doses examined. In contrast, intramammary peak pressure and its dissipation time were significantly larger in the 8- to 9-day lactators than in the 13- to 15-day lactators. The compliance of the mammary glands was indirectly assessed at the two stages of lactation. When a constant pressure pulse was introduced into a cannulated gland, the resulting pressure peak was significantly greater in 8-day than in 13-day lactators, indicating a greater resistance in the former. Taken together, these results indicate that when endogenous oxytocin is inhibited (by anaesthesia) the greater milk release observed at the later stage of lactation in response to various doses of oxytocin may be due to a decline in mammary resistance as lactation progresses.
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PMID:Mammary resistance: a possible controlling factor in milk ejection. 364 62

Plasma concentrations of oxytocin and vasopressin were measured in relationship to oxytocin cell firing during suckling in urethane-anaesthetized rats. Preliminary experiments showed that plasma concentrations of oxytocin and vasopressin, which were increased immediately after anaesthesia, reverted to basal concentrations 3 h later. Moreover, it was found that exogenous oxytocin had entirely disappeared 5 min after i.v. bolus injections of known doses of oxytocin. Suckling did not modify the basal plasma concentration of oxytocin (14.6 +/- 2.9 compared with 14.6 +/- 1.5 pmol/l before suckling) except during a brief period immediately after neurosecretory bursts on oxytocin cells (37.8 +/- 5.2 pmol/l; P less than 0.001, n = 11). The plasma concentration of oxytocin did not differ significantly from the basal concentration 1.5 min later. The plasma concentration of vasopressin never varied. After two neurosecretory bursts of similar amplitude (total number of spikes during the burst) recorded on the same oxytocin cell, the variations in plasma concentration of oxytocin were also similar. When, for a given cell, the amplitude of neurosecretory bursts increased or decreased, the amount of oxytocin released changed in the same way. These data demonstrate (1) that suckling induces pulsatile release of oxytocin without vasopressin, and (2) a direct relationship between the amounts of oxytocin released and the amplitude of oxytocin cell neurosecretory bursts which argue in favour of simultaneous increases or decreases in the neurosecretory burst amplitudes on all oxytocin cells.
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PMID:Relationship between oxytocin release and amplitude of oxytocin cell neurosecretory bursts during suckling in the rat. 365 14

The American College of Obstetricians and Gynecologists has supported the concept of a trial of labor in patients with a previous lower uterine transverse cesarean section, and its safety is generally accepted. The purpose of this report was to present the results of a year-long, prospective study in which the indications for trial of labor were liberalized. Only patients with a previous classical incision or "T" incision on the uterus were excluded. Two hundred seventy-two patients elected to undergo a trial of labor. Vaginal delivery occurred in 216 patients (76.5%). Oxytocin was used as needed, and epidural anesthesia was used in all patients who requested it. One uterine rupture occurred in a patient with a single lower transverse scar. The results of this study suggest that a trial of labor is a safe alternative for patients with a previous single or multiple lower uterine transverse incision or a lower uterine vertical incision. In addition, the use of epidural anesthesia and oxytocin appears safe in patients undergoing a trial of labor.
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PMID:Trial of labor in previous cesarean section patients, excluding classical cesarean sections. 365 77

Diurnal rhythms in the concentrations of vasopressin (AVP) and oxytocin in cerebrospinal fluid (CSF) differ between species and are unrelated to changes in the levels of these hormones in the peripheral circulation. We have investigated neurohypophysial hormone rhythms in the CSF of the conscious goat by determining whether they are entrained by daily cycles of light and darkness and by assessing the effect of the suppression of plasma cortisol. Goats were implanted with cisternal cannulae under halothane anaesthesia and allowed to recover. They were accustomed to a 12 h light:12 h darkness lighting cycle (lights on from 07.30 to 19.30 h). After initial serial CSF and plasma sampling the daily cycle of light and darkness was reversed. Three goats were kept in constant light for 8 days before the study and five were given dexamethasone (5 mg/12 h) for 4 days. There was a significant (P less than 0.01) diurnal variation in CSF concentrations of AVP, with a maximum of 3.6 +/- 0.8 (S.E.M.) pmol/l at 12.00 h and a minimum of 1.4 +/- 0.3 pmol/l at 24.00 h. There were no significant changes in CSF concentrations of oxytocin or plasma AVP. After the light:darkness cycle was reversed the AVP rhythm in the CSF was disrupted after 24 h and reversed after 8 days. The diurnal rhythm of AVP in CSF persisted in animals exposed to constant light. After treatment with dexamethasone plasma cortisol was suppressed and showed no diurnal rhythm but the AVP rhythm in CSF remained unchanged.
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PMID:Diurnal rhythm of vasopressin but not of oxytocin in the cerebrospinal fluid of the goat: lack of association with plasma cortisol rhythm. 366 36

The early pharmacokinetics of midazolam were compared in pregnant (active labour, awaiting and during elective Caesarean section) and matched gynaecological patients scheduled to undergo elective hysterectomy, half of whom were given an oxytocin infusion. A standard dose of 5 mg was given intravenously. For the first 15 minutes patients in labour had significantly higher plasma midazolam levels compared to all other groups. This was associated with the largest area under the curve (2 hours), the smallest volume of distribution and lowest clearance. Midazolam when given immediately before Caesarean section, can result in depression of the infant.
Anaesthesia 1987 Oct
PMID:A comparison of the early pharmacokinetics of midazolam in pregnant and nonpregnant women. 368 86


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