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

The ventromedial nuclei of the hypothalamus (VMN) are important for the control of feminine mating behavior, and hormone action within these nuclei has been causally related to behavior. Estradiol induces receptors for oxytocin in the VMN and in the area lateral to these nuclei over the course of 1 to 2 days, and progesterone causes, within 30 minutes of its application, a further increase in receptor binding and an expansion of the area covered by these receptors lateral to the VMN. The rapid progesterone effect appears to be a direct and specific effect of this steroid on the receptor or membrane, because it was produced in vitro as well as in vivo and was not mimicked by a variety of other steroids. The effect of progesterone occurred in the posterior part of the VMN, where oxytocin infusion facilitated feminine mating behavior; it did not take place in the anterior part of the VMN, where oxytocin infusion had no effect on mating behavior.
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PMID:Behavioral effects of progesterone associated with rapid modulation of oxytocin receptors. 217 39

The effects of administration of progesterone and oestradiol on ovine endometrial oxytocin receptor concentrations and plasma concentrations of 13,14-dihydro-15-keto prostaglandin F-2 alpha (PGFM) after oxytocin treatment were determined in ovariectomized ewes. Ewes received progestagen pre-treatment, progesterone and/or oestradiol in 11 different treatment schedules. Progestagen pre-treatment decreased oxytocin receptor concentrations in endometrium from ewes treated subsequently with either progesterone for 5 days or progesterone for 5 days plus oestradiol on Days 4 and 5 of progesterone treatment. Oestradiol increased endometrial oxytocin receptor concentrations when administered on Days 4 and 5 of 5 days progesterone treatment. Progestagen pre-treatment followed by progesterone treatment for 12 days caused a large increase in oxytocin receptors and no further increase occurred when ewes were given oestradiol on Days 11 and 12, or when progesterone was withdrawn on Days 11 and 12, or these two treatments were combined. Oxytocin administration caused an increase in plasma PGFM concentrations in ewes which did not receive progestagen pre-treatment, and subsequently received progesterone treatment for 5 days and oestradiol treatment on Days 4 and 5 of progesterone treatment. Similarly treated ewes which received progestagen pre-treatment did not respond to oxytocin. Oxytocin administration also increased plasma PGFM concentrations in ewes which received progestagen pre-treatment followed by progesterone treatment for 12 days, progesterone treatment for 12 days plus oestradiol on Day 11 and 12 of progesterone treatment, progesterone withdrawal on Day 11 and 12, or progesterone withdrawal and oestradiol treatment combined. The results indicate that (1) progesterone pre-treatment affects oxytocin receptor concentrations in the endometrium and uterine responsiveness to oxytocin and (2) progesterone treatment alone for 12 days after a treatment which mimics a previous luteal phase and oestrus is sufficient to induce oxytocin receptors and increase oxytocin-induced PGF release. These results emphasize the importance of progesterone and provide information which can be used to form an hypothesis for control of luteolysis and oestrous cycle length in the ewe.
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PMID:Control of endometrial oxytocin receptor and uterine response to oxytocin by progesterone and oestradiol in the ewe. 217 61

Oxytocin concentrations were measured radioimmunologically in sows on the day of standing oestrus over a 6-h period (controls, n = 6) or 1 h before and 5 h after mating (n = 5) or transcervical infusion of either 100 ml saline (0.9% (w/v) NaCl, n = 7) or saline plus 10 micrograms oestradiol (simulation of seminal oestrogens, n = 5). In the controls, oxytocin was low, at around 1.0 pmol/l, throughout the investigation period. Similarly, saline infusion did not lead to a noticeable change in oxytocin concentrations in six out of seven sows. In one sow, however, infusion led to a maximum of 86 pmol/l at 1 min after infusion. Oestradiol led to no immediate increase in oxytocin concentrations. Later in the post-treatment period (2-5 h) they were only slightly increased (1 pmol/l vs 3 pmol/l). All mated sows reacted with a rapid and clear increase in oxytocin. Maximal concentrations (42.0 +/- 5.1 pmol/l; mean +/- S.E.M.) appeared 2 min after the onset of ejaculation. Clearly increased concentrations were found for 40 min. It was concluded that mating specifically leads to a rise in oxytocin, probably due to both mechanical and pheromonal stimuli provided by the boar.
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PMID:Influence of mating and intra-uterine oestradiol infusion on peripheral oxytocin concentrations in the sow. 221 28

The oxytocin gene is maximally expressed in the cells of the early bovine corpus luteum (1-5 days post-ovulation) and provides an excellent marker for luteinization, having been up-regulated in vivo at ovulation. However, it is down-regulated again later in the luteal phase. To help understand the mechanisms involved in regulating this gene, and hence differentiation in the early bovine corpus luteum, oxytocin secretion into the medium as well as oxytocin mRNA were measured in serum-free cultures of early luteal cells in the presence or absence of various effectors. Insulin-like growth factor I (IGF-I) deferred the endogenous down-regulation of the gene and hence increased oxytocin peptide secretion in the first days of culture. Prostaglandin F2 alpha had no influence on oxytocin mRNA levels but reduced the stimulatory effect of IGF-I on peptide secretion, indicating an effect at the post-transcriptional level. Oestradiol had no effect either on oxytocin mRNA levels or on oxytocin secretion.
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PMID:The regulation of oxytocin gene expression in early bovine luteal cells. 234 Sep 52

Estrogen receptors are distributed in discrete areas of the hypothalamus, preoptic area and amygdala of the rat brain, and in some of these areas estrogens induce progestin receptor sites. Estradiol (E), followed by progesterone (P), induce feminine sexual behavior in female, but not in male, rats. This induction takes time (on the order of hours, not minutes, so that the hormone may be cleared from the body) and is dependent on RNA and protein synthesis. Within the hypothalamic ventromedial nuclei (VMN), E and P induce changes in RNA and protein synthesis and also induce morphological changes indicative of cellular growth, genomic activation, and either new synapse formation or morphological rearrangement of existing synapses. Neurochemically, a number of neurotransmitter systems are implicated in the control of feminine sexual behavior, including acetylcholine, serotonin, GABA, and the neuropeptides, oxytocin and CCK. One of the means by which E and P may exert their influence on sexual behavior, aside from the morphological alterations, is by regulating levels of receptors for certain of these neurotransmitters. The critical differences which underlie the inability of male rats to display high levels of feminine sexual behavior after E plus P priming may depend on sex differences in the ability of E to induce particular neurochemical products as well as P receptors and upon differences in neural circuitry in the VMN.
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PMID:Genomic regulation of sexual behavior. 245 98

Blood samples were collected frequently from permanent catheters placed in the aorta and caudal vena cava of 36 heifers in order to monitor the release pattern of LH, FSH, progesterone, oestradiol-17 beta, oxytocin, PGF-2 alpha, PGE-2 and PGI-2 (determined as its 6-keto-PGF-1 alpha metabolite). The frequency of secretory bursts of both gonadotrophins and progesterone was similar in early pregnant and cyclic animals, whereas the amplitude of LH and progesterone increased between 2 and 4 weeks of gestation. Concentrations of circulating oestradiol-17 beta and oxytocin were already lower at Days 4-7 in pregnant than in cyclic animals. Oestradiol-17 beta originated after Day 14 from the uterus rather than the ovary. A sustained release of oxytocin most probably from the posterior pituitary gland and a concomitant decrease of progesterone occurred in about two-thirds of pregnant animals during Days 19-23. Insemination could induce releases of PGF-2 alpha lasting up to 2 h. In addition, basal concentrations of PGF-2 alpha during the first 6 days after oestrus were approximately 2-fold higher in inseminated than in non-inseminated cyclic heifers. A parallel increase of PGF-2 alpha and PGI-2 occurred between Days 30 and 33 of gestation. Early embryonic mortality resulted, at least up to Day 35, in 4-7 concomitant secretory bursts of PGF-2 alpha and luteal oxytocin. There was a delay of 20-26 h between the first and second release. The present results from in-vivo experiments point towards major endocrine changes in cattle within a few days after conception, resulting in an early inhibition of follicular oestradiol-17 beta and luteal oxytocin facilitating the suppression of luteolytic releases of PGF-2 alpha.
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PMID:Sequences of pituitary, ovarian and uterine hormone secretion during the first 5 weeks of pregnancy in dairy cattle. 250 92

Oxytocin may function as a hypothalamic releasing hormone for prolactin and ACTH secretion in the rat. In the present study we have investigated the properties of putative oxytocin receptors in the rat adenohypophysis by radioligand-binding assay. A novel oxytocin receptor antagonist [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid),2-(ortho-methyl)-Tyr2-Thr4-Orn8-Tyr9-NH2]-vasotocin (OTA) was radioiodinated by the iodogen method to a specific activity of 0.6 nCi/fmol. The radioiodinated derivative 125I-labelled OTA (125I-OTA) was reacted with membrane suspensions prepared from the uterus or adenohypophysis of female rats which were (a) ovariectomized for 7 days, (b) ovariectomized and treated with 5 micrograms oestradiol-17 beta 48 h before death or (c) implanted with a piece of silicone elastomer tubing containing 50 mg diethylstilboestrol (DES) 5 days before death. In uterine as well as the pituitary membrane suspensions, the radioligand was bound reversibly and with high affinity (dissociation constants 0.2 +/- 0.1 and 0.1 +/- 0.01 nmol/l respectively; mean +/- S.E.M., n = 3) to a single class of sites with limited binding capacity, which varied with the type of pretreatment. Oestradiol-17 beta increased the binding capacity fivefold in the uterus in ovariectomized rats, but only very low specific radioligand binding was found in pituitary preparations from the same animals. Treatment with DES markedly increased the number of receptors in both the uterus and the adenohypophysis. Studies with several agonist and antagonist analogues revealed no difference in the ligand specificity of the uterine and adenohypophysial sites binding 125I-OTA, indicating that they are the same species of receptor.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characterization of oxytocin receptors in rat adenohypophysis using a radioiodinated receptor antagonist peptide. 254 59

Two ovarian hormones, estradiol and progesterone, which facilitate mating behavior in the female rat by acting on the ventromedial nuclei (VMN) of the hypothalamus, induce changes in oxytocin receptor binding in this brain region. Estradiol induced a 4-fold increase in the oxytocin receptor binding of the VMN and surrounding area and increased the number and immunostaining of oxytocin fibers in an area lateral to the ventral VMN. Progesterone, in estrogen-primed rats, caused the induced oxytocin receptors to spread over the area containing the oxytocin fibers. Infusion of oxytocin into the ventromedial hypothalamus increased the display of lordosis behavior only in females primed with both estradiol benzoate and progesterone. Thus, the sequential actions of two ovarian hormones bring a neuropeptide and its receptors into register and enable the neuropeptide to exert behavioral effects.
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PMID:Localized actions of progesterone in hypothalamus involve oxytocin. 254 47

Electromyographic (EMG) recordings were made during the last two weeks of pregnancy from two mares. Four bipolar EMG electrodes were implanted in the uteri of the mares; near the tubo-uterine junction and bifurcation of the pregnant horn, in the body of the uterus and near the cervix. Plasma samples were collected every 4 hours during the same period and more intensely during parturition. Estradiol 17 beta, progesterone, PGF2 alpha metabolite and oxytocin were measured by radioimmunoassay. During the last week preceding delivery, EMG activity was elevated and was greatest at night. EMG activity was further increased during the last 24 hours before delivery of the foal and reached its highest intensity for 7 to 13 hours immediately prepartum. This period of intense activity is described as stage I of parturition. EMG activity decreased to very low levels 2 to 4 hours before delivery but abruptly increased again at rupture of the choriollantois and continued through delivery when activity decreased again until delivery of the placenta. The ratio of estradiol 17 beta to progesterone (E 17 beta/P) increased through the last week prepartum due to an increase in the level of estradiol 17 beta concentrations and during the last 24 hours the change in the E 17 beta/P ratio was due to a significant decrease in progesterone. Oxytocin and PGF2 alpha metabolite increased abruptly just before rupture of the fetal membranes and there is some evidence that oxytocin increased prior to PGF2 alpha metabolite. We hypothesize that the increasing E 17 beta/P ratio allows the evolution of labor to occur during the daylight hours preceding parturition.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Pregnancy and labor in the mare: uterine activity and endocrinology]. 271 55

Bovine luteal cells from Days 4, 8, 14 and 18 of the estrous cycle were incubated for 2 h (1 x 10(5) cells/ml) in serum-free media with one or a combination of treatments [control (no hormone), prostaglandin F2 alpha (PGF), oxytocin (OT), estradiol-17 beta (E) or luteinizing hormone (LH)]. Luteal cell conditioned media were then assayed by RIA for progesterone (P), PGF, and OT. Basal secretion of PGF on Days 4, 8, 14 and 18 was 173.8 +/- 66.2, 111.1 +/- 37.8, 57.7 +/- 15.4 and 124.3 +/- 29.9 pg/ml, respectively. Basal release of OT and P was greater on Day 4 (P less than 0.01) than on Day 8, 14 and 18 (OT: 17.5 +/- 2.6 versus 5.6 +/- 0.7, 6.0 +/- 1.4 and 3.1 +/- 0.4 pg/ml; P: 138.9 +/- 19.5 versus 23.2 +/- 7.5, 35.4 +/- 6.5 and 43.6 +/- 8.1 ng/ml, respectively). Oxytocin increased (P less than 0.01) PGF release by luteal cells compared with control cultures irrespective of day of estrous cycle. Estradiol-17 beta stimulated (P less than 0.05) PGF secretion on Days 8, 14 and 18, and LH increased (P less than 0.01) PGF production only on Day 14. Prostaglandin F2 alpha, E and LH had no effect on OT release by luteal cells from any day. Luteinizing hormone alone or in combination with PGF, OT or E increased (P less than 0.01) P secretion by cells from Days 8, 14 and 18. However on Day 8, a combination of PGF + OT and PGF + E decreased (P less than 0.05) LH-stimulated P secretion. These data demonstrate that OT stimulates PGF secretion by bovine luteal cells in vitro. In addition, LH and E also stimulate PGF release but effects may vary with stage of estrous cycle.
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PMID:Prostaglandin F2 alpha, oxytocin and progesterone secretion by bovine luteal cells at several stages of luteal development: effects of oxytocin, luteinizing hormone, prostaglandin F2 alpha and estradiol-17 beta. 278 Oct 46


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