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

A combination of autoradiographical techniques and computerized image analysis has been used to study the distribution and density of cholecystokinin receptors in the paraventricular and supraoptic nuclei of animals in which the magnocellular-posterior pituitary axis is activated, namely, in salt-loaded (2% sodium chloride) and homozygous Brattleboro rats. [125I]cholecystokinin octapeptide binding was greatly elevated in the paraventricular, supraoptic and accessory nuclei of salt-loaded and homozygous Brattleboro rats, compared to the respective control animals. Furthermore, under these conditions [125I]cholecystokinin octapeptide binding in the paraventricular nucleus was localized almost exclusively to magnocellular subdivisions, and especially to those containing predominantly oxytocin neurons. Autoradiographical competition studies revealed that the increase in [125I]cholecystokinin octapeptide binding in magnocellular nuclei reflected an increase in receptor number (Bmax) rather than affinity (Kd). These results suggest that cholecystokinin receptor density in the paraventricular, supraoptic and accessory magnocellular nuclei is closely linked to magnocellular neurosecretory activity and raises the possibility that cholecystokinin receptors may be involved in oxytocin and vasopressin release processes.
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PMID:Modulation of hypothalamic cholecystokinin receptor density with changes in magnocellular activity: a quantitative autoradiographic study. 272 63

Pinealectomized (PX), sham-operated and non operated control rats were injected intraperitoneally (i.p.), once daily at 8.00 over five days, with: (a) 0.9% sodium chloride, (b) propranolol hydrochloride in a dose of 10 mg/kg (= 0.1 ml solution per 100 g b.w.). Three hours following the last injection the animals were decapitated and the content of vasopressin and oxytocin was bioassayed in the hypothalamus and neurointermediate lobe. PX was followed by known decrease of both vasopressin and oxytocin in the hypothalamus and neurohypophysis. In rats not-PX propranolol did not change the vasopressin and oxytocin content in the hypothalamus and neurointermediate lobe. In PX-rats, treatment with propranolol resulted in a distinct increase of the vasopressin in the neurohypophysis. It may be therefore supposed that the beta-adrenergic transmission is in some way involved in the regulatory mechanisms of pineal-neurohypophysial functional relationship.
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PMID:The effects of beta-adrenergic blockade on the hypothalamic and neurohypophysial vasopressin and oxytocin content in pinealectomized male rats. 288 9

The effect of the intracerebroventricular (i.c.v.) injection of hypertonic sodium chloride on plasma atrial natriuretic peptide (ANP) and oxytocin (OT) was evaluated in conscious freely moving rats. A hypertonic or isotonic NaCl solution was injected into the third ventricle. Blood pressure and heart rate were monitored and blood samples were collected. I.c.v. injection of the hypertonic solution resulted in a significant increase in mean arterial pressure (105.3 +/- 2.9 mmHg at time 0 to 124.2 +/- 4.4 mmHg at 5 min, P less than 0.01) and heart rate (350.0 +/- 25.0 bpm at time 0 to 420.8 +/- 13.6 bpm at 20 min, P less than 0.01). Plasma OT increased 4-fold over the basal values 5 min after the injection (4.5 +/- 1.1 to 20.1 +/- 3.2 pg/ml, P less than 0.01), while there was no significant change in plasma ANP (37.3 +/- 9.1 to 46.6 +/- 12.6 pg/ml, n.s.). The control injection produced no significant changes in any parameters. These results show that hemodynamic changes are not necessarily associated with alterations in plasma ANP. Furthermore they suggest that central osmoreceptors are not involved in the control of ANP secretion.
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PMID:Effect of central hypertonic stimulation on plasma atrial natriuretic peptide and oxytocin in conscious rats. 297 58

Rats dehydrated for 8 days and subsequently rehydrated were given intracerebroventricularly (i.c.v.) methoxamine hydrochloride (MX) or dihydroergotamine methanosulphonate (DHE), each in a daily dose of 10 micrograms dissolved in 10 microliter of 0.9% sodium chloride. A single dose of MX injected to normally hydrated animals increased the release of hypothalamic and neurohypophysial vasopressin but did not affect significantly the oxytocic activity in the hypothalamus as well as in the neurohypophysis. Under conditions of dehydration MX did not influence the hypothalamic vasopressin content but it stimulated the neurohypophysial vasopressin depletion. On the contrary, MX distinctly inhibited the decrease of hypothalamic and neurohypophysial oxytocin content in dehydrated animals. In rehydrated animals MX restrained some what the renewal of hypothalamic vasopressin and oxytocin storage but intensified this process in the neurohypophysis. A single dose of DHE decreased the vasopressin content in the hypothalamus as well as the oxytocin content both in the hypothalamus and neurohypophysis. Under conditions of dehydration DHE stimulated the depletion of hypothalamic vasopressin and oxytocin. On the contrary, DHE strongly inhibited the depletion of oxytocin in the neurohypophysis of dehydrated rats. DHE restrained the renewal of hypothalamic vasopressin and oxytocin stores as well as intensified this process in the neurohypophysis of subsequently rehydrated rats.
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PMID:The hypothalamic and neurohypophysial vasopressin and oxytocin content under various states of adrenergic transmission in dehydrated and subsequently rehydrated rats. 301 81

In a single-blind study 51 patients with retention of the placenta were randomized into one of three groups: Group 1 was given 10 IU of oxytocin in 10 ml of sodium chloride into the umbilical vein; group 2 was given 10 ml of sodium chloride; group 3 was treated with manual removal of the placenta. No significant differences were recorded in groups 1 and 2, and no advantages were found in comparison with the procedure normally used.
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PMID:The effect of oxytocin injection into the umbilical vein for the management of the retained placenta. 355 83

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

Activity of 40 single antidromically identified supraoptic neurons was recorded and evaluated in response to a combination of tactile, vulvar massage, vaginal distension, and slow intrajugular 1.2 M sodium chloride infusion in unanesthetized, randomly hydrated ewes. Estradiol-implanted Southdown ewes were prepared according to techniques described by Jennings et al. Only 4 spontaneous firing patterns were observed in the supraoptic nuclei. Analysis of evoked activity indicated that each stimulus evoked alterations in mean firing rates or increased numbers of short interspike intervals in some cells. The resultant activity of units to sequential vulvar massage and 1.2 M sodium chloride infusion suggests a possibility of separate mechanisms of release of oxytocin and vasopressin.
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PMID:Effects of intrajugular hypertonic saline, vaginal distension and vulvar massage on activity of supraoptic neuroendocrine cells. 397 Nov 61

Morphine was injected into the lumbar subarachnoid space of anaesthetized lactating rats (7-10 days post partum) to examine its effect on the milk-ejection reflex at a spinal level. Although the delay until the first milk-ejection response to the suckling of hungry pups was variable (3-60 min) the subsequent responses occurred at regular intervals of 7.5 +/- 0.4 min; milk-ejection responses were detected by measurement of intramammary pressure and by the characteristic behaviour of the pups. Injection of morphine (4-50 micrograms) via a cannula inserted into the spinal subarachnoid space inhibited reflex milk ejection in a dose-related manner without affecting the sensitivity of the mammary gland to exogenous oxytocin (1 mu., i.v.); injection extradurally was without effect. The opiate antagonist naloxone (10 micrograms), when injected intrathecally, did not significantly alter the pattern of reflex milk ejection or the amplitude of the intramammary pressure response, but prevented the inhibitory effect of morphine when administered with the opiate. Pethidine (250 and 400 micrograms) also inhibited the milk-ejection reflex. It is unlikely that the effect of spinal administration of morphine occurred as the result of the transportation to a supraspinal site since release of oxytocin evoked by intraventricular injection of hypertonic sodium chloride (3 mol/l) was blocked by intraventricular injection of morphine (4 micrograms) but not by a much larger dose (40 micrograms) injected intrathecally.
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PMID:Evidence for a spinal site at which opioids may act to inhibit the milk-ejection reflex. 404 47

1. Electrical recordings were made from antidromically identified supraoptic and paraventricular units during intracarotid injections of hypertonic and isotonic sodium chloride solutions in rats.2. The blood concentrations of vasopressin and oxytocin were estimated by bio-assay before and at different intervals after similar injections.3. Although a significant change in the action potential activity of the supraoptic nucleus was associated with hormone release, the results were not entirely consistent with a simple relationship between action potential activity and hormone secretion. Firstly, although some units were excited by the stimulus a substantial number were inhibited. Secondly, the blood concentration of the hormones, particularly ADH, remained elevated for longer than might have been expected if additional hormone had ceased to be secreted as soon as firing rates had returned to control values.4. There were substantial differences between the initial blood concentrations of vasopressin and oxytocin but the firing rates of units in the supraoptic and paraventricular nuclei appeared to be the same.5. Although significantly less paraventricular than supraoptic units were affected by hypertonic injections the blood concentration of oxytocin was increased by a factor of 8 whereas that of vasopressin was increased by a factor of 2.7.
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PMID:Oxytocin and ADH secretion in relation to electrical activity in antidromically identified supraoptic and paraventricular units. 557 37

1. The effect of intramuscular injection of 8-arginine vasotocin, 8-arginine vasopressin, 8-lysine vasopressin, oxytocin, 8-ornithine oxytocin and 8-ornithine vasopressin on fluid uptake across the skin was studied in the live toad, Bufo melanostictus, bathed either in distilled water or in NaCl solution (0.1 g/100 ml.).2. When the bathing solution was distilled water, 8-arginine vasotocin was the most potent, 0.14 nmole/kg augmenting the rate of fluid uptake by 50%. Compared with it the others had relative potencies of: 8-arginine vasopressin 0.8, 8-lysine vasopressin 0.8 x 10(-3), oxytocin 0.8 x 10(-3), 8-ornithine oxytocin 0.8 x 10(-2), 8-ornithine vasopressin < 1.4 x 10(-4).3. When the bathing solution contained 0.1% NaCl, 8-arginine vasotocin was again the most potent, 0.06 nmole/kg augmenting the rate of fluid uptake by 50%. Compared with it the others had relative potencies of: 8-arginine vasopressin 0.3, 8-lysine vasopressin 0.3 x 10(-3), oxytocin 0.3 x 10(-2), 8-ornithine oxytocin 0.8 x 10(-2), 8-ornithine vasopressin < 0.6 x 10(-4).4. Dose-response curves for each peptide showed that in the case of 8-arginine vasopressin, 8-lysine vasopressin and 8-ornithine vasopressin the augmentation of rate of fluid uptake did not differ in the absence or in the presence of NaCl in the bathing solution; whereas in the case of 8-arginine vasotocin, oxytocin, and 8-ornithine oxytocin the augmentation was greater in the presence of sodium chloride.5. Support has been found for the postulate of a binary action of some neurohypophysial peptides on amphibian skin, arginine in position 8 being correlated with hydrosmotic effect, and isoleucine in position 3 with natriferic effect.
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PMID:Natriferic and hydrosmotic effects of neurohypophysial peptides and their analogues in augmenting fluid uptake by Bufo melanostictus. 567 41


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