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

Human myometrial visceral and vascular preparations and placental chorionic and stem villous vessels were dissected from myometrial and placental specimens obtained at term Caesarean section and after vaginal delivery. Vascular ring preparations and myometrial strips were mounted in organ bath and isometric tension recorded. Only myometrial preparations developed spontaneous contractile activity, which was effectively blocked by the calcium channel blocker nitrendipine (NTD) 10(-7) M. Pretreatment with calcium-depleted medium for 30 min. almost abolished myometrial responses to high K+ (124 mmol), oxytocin (OX) and prostaglandin F2 alpha (PGF2 alpha). Vascular responses to high K+ (124 mmol) were also nearly abolished by such treatment. However, noradrenaline (NA), vasopressin (VP) and PGF2 alpha in myometrial arteries and PGF2 alpha in chorionic vessels and stem villous arteries induced significant, but reduced contractions after calcium depletion. In all vascular preparations, exposed to calcium-depleted medium, NTD (10(-8) M) almost abolished contractions induced by calcium (0.1-4.0 mM) in the presence of K+ (124 mmol) and depressed responses to calcium in the presence of the other agonists tested. NTD (10(-10)-10(-7) M) depressed myometrial contractions induced by K+, OX and PGF2 alpha more effective than vascular responses to K+, NA, VP and PGF2 alpha in the myometrial arteries and K+ and PGF2 alpha in the placental arteries. It is concluded that activation of contraction in vessels from the human utero-placental unit implies multiple cellular sources of calcium, while in myometrial smooth muscle, influx of superficially bound calcium may be an important initial step in contractile activation. Treatment with calcium channel blockers during late human pregnancy might involve relaxation of the myometrium together with vasodilatation of the myometrial and foetal placental vascular beds.
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PMID:Inhibitory effects of nitrendipine on myometrial and vascular smooth muscle in human pregnant uterus and placenta. 346 59

Noradrenaline (NA) (1-100 microM) was applied to 41 neurons recorded intracellularly from the supraoptic nucleus (SON) of the rat hypothalamic slice preparation; 34 (83%) neurons showed membrane depolarization which was dose-dependent. The depolarization was frequently accompanied by decreased membrane resistance, increased firing rate and increased fluctuations in membrane potential. Following the application of the alpha-agonist, phenylephrine, 10 out of 11 neurons tested showed similar responses, while the beta-agonist, isoproterenol, caused no changes in 6 out of 7 SON cells. We found no difference in responsiveness between neurons having a 'phasic' or a 'non-phasic' pattern of firing. We conclude that NA depolarized and increased the firing rate of both vasopressin- and oxytocin-containing neurons through an action on alpha-adrenergic receptors.
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PMID:Depolarizing effect of noradrenaline on neurons of the rat supraoptic nucleus in vitro. 356 13

The effects of catecholamines and ascorbic acid on cultured bovine granulosa cells have been examined to assess their possible role in the initiation and maintenance of luteal oxytocin secretion. The actions of these agents have also been compared with the previously reported ability of follicular theca tissue to enhance oxytocin secretion. Using granulosa cells cultured in serum-supplemented medium, we observed a highly significant enhancement of oxytocin secretion in the presence of adrenaline and noradrenaline, particularly over the concentration range 1-10 mumol/l. This effect was accompanied by smaller and less consistent changes in progesterone secretion and did not involve any change in the time-course of oxytocin secretion. Acetylcholine was without effect. Ascorbic acid stimulated oxytocin secretion when used alone over a range of concentrations, but was also able to synergize with adrenaline. Lactic acid was ineffective. The stimulation of oxytocin secretion by adrenaline could be blocked by equimolar propranolol, but the stimulation of progesterone was not blocked. Propranolol had a variable effect on the ability of theca tissue to stimulate oxytocin secretion by granulosa cells but the results also suggested the presence of some beta-agonistic activity in the culture medium. We conclude, first, that catecholamines may be involved in the regulation of ovarian oxytocin secretion, secondly, that ascorbate may regulate oxytocin secretion through its involvement in the biosynthesis of oxytocin but also through interaction with catecholamines and, thirdly, that the stimulatory action of theca tissue probably does not involve the action of beta-agonists.
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PMID:Catecholamines and ascorbic acid as stimulators of bovine ovarian oxytocin secretion. 366 32

The concentrations of immunoreactive oxytocin and arginine vasopressin (AVP) and their respective neurophysins (NpI and NpII) were compared in bovine adrenal cortex and medulla. While the concentration of AVP was similar in both tissues there was more NpII in the medulla. The medulla also contained much more oxytocin and NpI than the cortex. The extracted AVP and oxytocin had identical retention times to those of the synthetic peptides on high-performance liquid chromatography (HPLC) and were biologically active in assays for antidiuretic and milk-ejection activity (with potencies of 310 units/mg and 340 units/mg respectively). Adrenal NpI and NpII behaved identically to commercially available neurohypophysial proteins on HPLC. Oxytocin, NpI and AVP were assayed in five subcellular fractions of bovine adrenal medulla prepared on discontinuous sucrose gradients. A high proportion of each co-localized with noradrenaline and adrenaline in the chromaffin granule fraction. Binding of [3H]AVP and [3H]oxytocin to crude bovine adrenal medulla membranes was dependent upon both time and temperature. The binding sites were specific and saturable: studies with the V1 AVP antagonist d(CH2)5Tyr(Me)AVP and the V2 agonist 1-deamino-8-D-AVP indicated that the AVP receptor was V1 in specificity. Scatchard plots showed that each ligand interacted with a single high-affinity, low-capacity binding site: oxytocin dissociation constant (Kd) 3.1 +/- 0.29 nmol/l, maximum binding capacity (Bmax) 89.6 +/- 18.4 fmol/mg protein (n = 3); AVP Kd 0.73 +/- 0.02 nmol/l, Bmax 26.5 +/- 8.3 fmol/mg protein (n = 3).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Arginine vasopressin and oxytocin in the bovine adrenal gland. 366 43

The possibility of a functional relationship between noradrenaline and neurohypophyseal peptides in the control of cardiovascular function in the nucleus tractus solitarius of rats has been investigated. The hypotensive response to microinjections of noradrenaline (20 nmol) was abolished by simultaneous (but not prior) microinjections of [Arg8]vasopressin (AVP) and oxytocin at doses (0.9 pmol) which alone had no effects on cardiovascular parameters. AVP plus noradrenaline actually resulted in a transient pressor effect. Simultaneous administration of [deamino-D-Arg8]vasopressin, a selective agonist of AVP V2 receptors, did not modify the effect of noradrenaline, whereas the specific V1 antagonist D-(CH2)5-Tyr(Me)-AVP partially decreased its intensity. When subthreshold doses of both AVP (0.9 pmol) and noradrenaline (10 pmol) were administered simultaneously, a pressor response was observed. In vasopressin-deficient Brattleboro rats, microinjections of 0.9 pmol AVP had no effects, but a marked pressor response was observed after the administration of a higher dose (9 pmol). In parent strain Long-Evans rats, noradrenaline (20 nmol) also produced a hypotensive response, but in Brattleboro rats microinjections of this amine elicited a marked pressor effect. In these rats, simultaneous administration of a subthreshold dose of AVP (0.9 pmol) reversed this response in such a way that a fall in blood pressure, similar to that observed in Long-Evans rats after injection of noradrenaline alone, was registered. These results provide evidence for a functional interaction between noradrenaline and neurohypophyseal peptides in the control of cardiovascular function in the brainstem.
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PMID:Evidence for a functional relationship between noradrenaline and neurohypophyseal peptides in the brainstem of rats. 367 90

Cervical specimens were obtained by needle biopsy in connection with caesarean section at term pregnancy. The preparations were superfused in an organ chamber and contractions were registered isometrically. Prostaglandin (PG) E2 and F2 alpha inhibited spontaneous contractions. The stimulatory action of noradrenaline was not influenced by PGF2 alpha but was reduced by PGE2 whereas both PGs abolished the excitatory effect of oxytocin.
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PMID:Effects of PGE2 and PGF2 alpha on the simulation by noradrenaline and oxytocin of human cervical muscle activity at term. 386 43

Vasopressin-and neurophysin-immunoreactive cells have recently been demonstrated in the rat locus coeruleus (A6) and subcoeruleus (A7). Using consecutive 5 microns thick frozen sections, medium-sized cells throughout the locus coeruleus area, but predominantly in the posterior parts of the A6 displayed coexistence for vasopressin and noradrenaline or neurophysin and noradrenaline immunoreactivity. The putative projection areas of putative fibers from vasopressin-containing cells in the locus coeruleus still remain to be elucidated.
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PMID:Coexistence of vasopressin, neurophysin and noradrenaline immunoreactivity in medium-sized cells of the locus coeruleus and subcoeruleus in the rat. 389 92

Peptides and non-peptides acting as vasoconstrictors or vasodilators have been tested in dog isolated carotid arteries with and without endothelium and in the presence and absence of a variety of antagonists and inhibitors of endogenous substances. It has been found that substance P and several other tachykinins, bradykinin, neurotensin, bombesin and acetylcholine relax the isolated artery only when the endothelium is present, while VIP, isopropylnoradrenaline, adenosine, histamine, prostaglandins E1 and E2, glucagon and insulin relax and angiotensin, vasopressin, oxytocin, 5-HT and noradrenaline contract the isolated vessel, no matter whether the endothelium is present or not. Peptide and non-peptide antagonists have been used with success to show that vasoconstrictors and vasodilators act on specific receptors, since their effects are reduced in the presence of antagonists, specific for one or another of the various agents. Inhibitors of the arachidonic acid cascade only reduce the effect of acetylcholine, suggesting that at least two different mechanisms are involved in the endothelium-mediated relaxation of arterial smooth muscles to peptide and non-peptide agents. The results summarised in this paper suggest that the site of action of several vasodilators is the endothelium, while other vasodilators and all the vasoconstrictors influence the arterial vessels tone presumably by acting on the smooth muscle cells.
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PMID:Effects of peptides and non-peptides on isolated arterial smooth muscles: role of endothelium. 393 Feb 67

A modification of the rat isolated seminal vesicle preparation is described, emphasizing the necessity to use younger animals (40-50 days old and weighing between 125 and 150 g) and to expel thoroughly all vesicular contents. Under the experimental conditions used (tissues suspended under a resting tension of 350 mg in a continuous flow of a modified Krebs solution run at the rate of 15 ml/min, maintained at 32 degrees C, and bubbled with 5% CO2 in O2), the preparation was quite sensitive, but only to a few selected agonists, and remained viable for over 4-6 hr. Adrenaline, noradrenaline, dopamine, and acetylcholine all produced concentration-dependent and reproducible contractions. However, histaminergic, serotoninergic, purinergic, and opioid agonists were inactive as were prostaglandins of the E and F series and the polypeptides angiotensin, vasopressin, and oxytocin. In general, the tissue was rather insensitive to relaxant drugs, with only papaverine and sodium nitrite producing some relaxation in tissues previously contracted by carbachol. Advantages of the preparation include marked responsiveness, but only to a few selected agonists, and suitability for use as a paired tissue. It is suggested that employed under suitable experimental conditions, the preparation deserves a more frequent consideration for use during pharmacological investigations concerned with postsynaptic aspects of noradrenergic or cholinergic transmission.
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PMID:Pharmacological evaluation of the isolated rat seminal vesicle preparation. 395 Dec 38

An assessment was made of the potencies of nifedipine, gallopamil, diltiazem, cinnarizine and salbutamol as inhibitors of tension development by the uterus and cardiovascular tissues from the term pregnant rat. The rank order of potency was nifedipine greater than gallopamil greater than diltiazem for those preparations on which these compounds were potent, viz. spontaneous and oxytocin-induced tension development of the uterus, spontaneous tension development of hepatic portal vein, potassium chloride (KCl)-induced pressure rises of perfused mesenteric bed and electrically-stimulated (0.5 Hz) ventricular muscle. The rank order of potency of nifedipine, gallopamil and diltiazem was different for those preparations on which they exhibited low potency, viz. noradrenaline-induced pressure rises of perfused mesenteric bed and tension development of aorta. Gallopamil and diltiazem, but not nifedipine, were more potent against tension development by ventricular muscle stimulated at 2.5 Hz than at 0.5 Hz, suggesting that nifedipine interacts at a different site from the other compounds. Cinnarizine was less potent than the other calcium antagonists on the uterus and portal vein, was the second most potent compound against KCl-induced pressure rises of the mesenteric bed and was equipotent against responses to noradrenaline and KCl of the mesenteric bed (unlike the other compounds). This suggests that the site of action of cinnarizine differs from that of the other calcium antagonists. Nifedipine, gallopamil and diltiazem, like salbutamol, exhibited selectivity for inhibition of tension development by the uterus relative to the cardiovascular tissues.
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PMID:A comparison of several calcium antagonists on uterine, vascular and cardiac muscles from the rat. 402 68


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