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

Oxytocin receptors were identified and characterized in bovine mammary tissue. [3H]-oxytocin was specifically bound to the 105,000 X g particulate fractions from 5 lactating cows and 5 non-lactating cows. Binding reached equilibrium by 50 min at 20 degrees C and by 8 hr at 4 degrees C. The half-time of displacement at 20 degrees C was approximately 1 hr. ACTH, TRH, angiotensin I, angiotensin II, pentagastrin, bradykinin, xenopsin and L-valyl-histidyl-L-leucyl-L-threonyl- L-prolyl-L-valyl-L-glutamyl-L-lysine were not competitive in the dose range tested at 20 degrees C. The ability of other peptides to inhibit 3H-oxytocin binding was as follows: oxytocin greater than vasotocin greater than arginine - vasopressin greater than lysine - vasopressin greater than Pen1 Phe2 Thr4 - oxytocin. The Kd of the oxytocin receptor averaged 1.66 +/- 1.19 nMol/L for lactating cows and 0.97 +/- nMol/L for non-lactating cows, respectively. The maximum number of binding sites was 0.14 +/- 0.12 nM/mg protein and 0.15 +/- 0.08 nM/mg protein for lactating cows and non-lactating cows, respectively. Identification and characterization of these receptors now makes it possible to study the dynamics of hormonal binding throughout various physiological states of the animal.
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PMID:Oxytocin receptors in bovine mammary tissue. 282 Dec 49

We previously reported that the rat posterior pituitary contains a potent PRL-releasing factor (PRF) which is distinct from oxytocin (OT), TRH, and angiotensin II (AII). The objectives of this study were 1) to examine whether posterior pituitary extracts stimulate PRL release in the presence of dopamine (DA), 2) to determine the chemical nature of PRF, and 3) to estimate its mol wt. Perifused anterior pituitary cells were used to assess PRF activity. Posterior pituitaries and medial basal hypothalamus (MBH) fragments were extracted with perchloric acid and lyophilized. Subsequent to various treatments, samples were reconstituted in the perifusion medium and introduced to the cells in short pulses. Fractions were collected and analyzed for hormone content by RIA. During a constant infusion of DA (50 nM), PRL secretion was inhibited by 75%, yet the posterior pituitary extract retained its ability to rapidly stimulate PRL release. Studies using proteolytic enzymes showed that posterior pituitary PRF was resistant to inactivation by trypsin, whereas the PRF activity of AII was abolished. Both chymotrypsin and proline-specific endopeptidase significantly reduced the PRF activity in the posterior pituitary. The PRL-releasing activity of TRH was not affected by chymotrypsin. Immunoreactive vasoactive intestinal polypeptide was undetectable in posterior pituitary extracts. Oxidation of posterior pituitary extracts with performic acid caused only a modest reduction of their PRF activity, while the ability of OT to stimulate PRL release as well as immunoreactive OT was abolished. Studies using ultrafiltration membranes showed that the PRF activity in the posterior pituitary was less than 5,000 mol wt. Furthermore, posterior pituitary PRF partitioned in nearly equal amounts across 1K membranes, as did AII and OT. In contrast, about 80% of the PRF activity in the MBH and all of the synthetic TRH passed through the 1K membranes. We conclude that 1) posterior pituitary PRF can stimulate PRL secretion from perifused anterior pituitary cells in the presence of physiological concentrations of DA; 2) PRF is a small peptide(s) of less than 5,000, and perhaps closer to 1,000, mol wt; 3) PRF is resistant to inactivation by trypsin and to oxidation by performic acid, but is hydrolyzed by both chymotrypsin and proline-specific endopeptidase; and 4) these data further distinguish posterior pituitary PRF from known PRL secretagogues.
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PMID:Characterization of prolactin-releasing factor in the rat posterior pituitary. 313 Nov 18

The observation that suckling evokes a modest rise in serum TSH when compared with that of prolactin is inconsistent with the hypothesis that TRH serves as a hypophysiotropic mediator of this response. In the present study we attempted to provide an explanation for this discrepancy by determining whether any of a growing number of putative prolactin releasing factors could alter pituitary responsiveness to TRH. Anterior pituitaries from lactating (day 14) rats were monodispersed with trypsin, cultured for 2 days, and then incubated in the presence of medium alone or medium containing TRH, dopamine, or a combination of these secretagogues. Companion sets of cultures were incubated concurrently with either beta-endorphin, neurotensin, oxytocin, serotonin, vasoactive intestinal polypeptide, or lysine vasopressin. As expected, TRH stimulated and dopamine suppressed prolactin release. None of the substances tested except oxytocin had a significant effect on pituitary cell responsiveness to TRH or dopamine. Oxytocin had no effect on prolactin secretion when tested alone or in combination with TRH and dopamine. TRH alone stimulated TSH release by these cultures, while oxytocin and dopamine were ineffective by themselves. However, TSH secretion by cultures treated simultaneously with TRH and oxytocin could be suppressed to approximately half of that released by cells incubated with TRH alone. These results demonstrate that oxytocin attenuates TRH-induced TSH release by a direct action on pituitary cells without affecting the prolactin response. This selectivity of responsiveness imparted by oxytocin might contribute to the blunted release of TSH after suckling.
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PMID:Oxytocin attenuates TRH-induced TSH release from rat pituitary cells. 315 75

Since neuroimmunomodulation is brought about in part, at least, by secretion of pituitary hormones involved in stress and immune responses, we review briefly the hypothalamic control of the release of ACTH, growth hormone, and prolactin. The release of ACTH is controlled particularly by corticotropin-releasing factor (CRF), but vasopressin has intrinsic releasing activity and potentiates the action of CRF at both hypothalamic and pituitary levels. Oxytocin may even potentiate the action of CRF, but has little, if any, ACTH-releasing activity by itself. In addition, epinephrine may augment responses to the CRFs. In contrast, growth hormone is under dual control by growth-hormone-releasing factor (GRF) and somatostatin, and prolactin is under multifactorial control by a series of inhibitors and stimulators. Dopamine is accepted as a physiological prolactin-inhibiting factor (PIF), but probably GABA and possibly acetylcholine as well are PIFs. There is good evidence for a peptide PIF as well. There are a number of prolactin-releasing factors (PRFs) which include oxytocin, vasoactive intestinal polypeptide, PHI and TRH. Several other peptides can also release prolactin, including angiotensin II. In response to stress there is a complex interaction of peptides intrahypothalamically. CRF augments its own release by an ultra short-loop positive feedback, and there is negative ultra short-loop feedback of GRF and somatostatin. Vasopressin appears to augment CRF release as well as to act directly on the pituitary, and there are complex interactions of various peptides to influence prolactin and GH release.
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PMID:The role of brain peptides in neuroimmunomodulation. 347 67

A tabular synopsis is presented for articles concerned with the effects of peptides on the central nervous system that appeared in the journal Peptides from 1980-1985. A table arranged alphabetically by peptide and one arranged by effects, both listing routes of injection, species, direction of change, and qualifying notes, provides easy cross-referencing of peptides and their effects. Over 80 peptides and over 135 effects are listed. The list of peptides includes, but is not limited to: ACTH, angiotensin, bombesin, bradykinin, calcitonin, casomorphin, CCK, ceruletide, CGRP, CRF, dermorphin, DSIP, dynorphin, endorphins, enkephalins, GRF, gastrin, LHRH, litorin, metkephamid, MIF-l, motilin, MSH, NPY, NT, oxytocin, ranatensin, sauvagine, substances P and K, somatostatin, TRH, VIP, vasopressin, and vasotocin. The list of effects includes, but is not limited to: aggression, alcohol, analgesia, attention, avoidance, behavior, cardiovascular regulation, catalepsy, conditioned behavior, convulsions, dopamine binding and metabolism, discrimination, drinking, EEG, exploration, feeding, fever, gastric secretion, GI motility, grooming, learning, locomotor behavior, mating, memory, neuronal activity, open field, operant behavior, rearing, respiration, satiety, scratching, seizure, sleep, stereotypy, temperature, thermoregulation and tolerance.
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PMID:Central nervous system effects of peptides, 1980-1985: a cross-listing of peptides and their central actions from the first six years of the journal Peptides. 353 8

Injections of oxytocin and TRH (11 picomoles), centered on the dorsal motor nucleus of the vagus, substantially increased gastric acid secretion. Additionally, oxytocin, but not TRH, simultaneously produced a consistent reduction in heart rate. Vasopressin injected into the same locus, at doses of 11 and 110 picomoles, had no effect on either function. Both the gastric and cardiac effects of oxytocin were eliminated by the central injections of oxytocin antagonist dEt2Tyr(Et)Orn8Vasotocin (ETOV; 6 picomoles) or peripheral administration of atropine (300 micrograms/kg, IP). Application of oxytocin or TRH to the area postrema, at double the dosage (22 picomoles) yielded no consistent effects on either gastric secretion or heart rate. These findings indicate that oxytocin in the dorsal motor nucleus of the vagus may act as a regulator of vagally-mediated gastric and cardiovascular functions while TRH effects, in this medullary area, seem limited to the regulation of gastric function.
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PMID:Dorsal medullary oxytocin, vasopressin, oxytocin antagonist, and TRH effects on gastric acid secretion and heart rate. 393 42

While previous reports have immunocytochemically localized oxytocin and TRH in the spinal cord, the functional significance of these peptides is unclear. The present paper examined this issue and tested the effects of these peptides upon intrathecal administration. We found both peptides produced lasting motor and blood pressure changes. Oxytocin elicited prolonged jerks of the hindlimbs and the tail, while TRH produced an increase of hindlimb muscle tone and tail tremor. TRH in larger doses (5, 10 micrograms) also caused tail erections and whipping. The motor effects of both peptides were dose-dependent. Intrathecal oxytocin (0.75 or 1.5 IU) caused a transient drop in blood pressure followed by a rise, in 4 out of 7 rats. The other 3 only showed a hypertensive effect. In contrast, intrathecal TRH produced a rise in blood pressure in all the animals tested. These findings suggest that both oxytocin and TRH may play a role in the regulation of motor and automatic functioning at the spinal level.
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PMID:Differential motor and blood pressure effects of intrathecal oxytocin and TRH in the rat. 393 43

The review article summarizes the results obtained in the author's laboratory during the last few years concerning the action of number of neurohormones such as ACTH, vasopressin, oxytocin, TRH and TRH analogues, human chorionic gonadotropin (HCG) LH-RH, gastrin and gastrin C-terminal fragments and cholecystokinin octapeptide on certain behavioural reactions and brain transmitters. The results obtained suggests that in some of the behavioural reactions elicited by these peptide hormones are brought about by modulatory action of these peptide on brain transmitters. These neurohormones, including gastrointestinal peptide hormones have a time dependent, locus and transmitter specific action on the brain function.
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PMID:The effect of neurohormones on the brain and the endocrine system. 611 Mar 9

125I-angiotensin II (125I-AII) binding was examined in the hypothalamic-thalamic-septal-midbrain (HTSM) region of HLA-Wistar rats in the presence of CNS-active agents. Angiotensin I, II, and III and saralasin competed for 125 I-AII binding, whereas structurally unrelated peptides such as arginine and lysine vasopressin, oxytocin, LHRH, TRH, bradykinin, and substance P did not. In contrast, ACTH and neurotensin exhibited a weak, dose-dependent competition for 125 I-AII binding. The relative potencies of AII, AI, neurotensin and ACTH were 100:1:0.1:0.05, respectively. Neurotensin and ACTH competition was not additive with AII suggesting interaction at shared binding sites. Most importantly, a wide variety of other CNS active agents such as methyldopa, naloxone, catecholamines, clondidine, and reserpine, failed to inhibit 125 I-AII binding, thus further defining the specificity of the CNS AII receptor.
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PMID:The specificity of angiotensin II receptor binding in rat brain. 627 72

Most neuropeptides are known to occur both in the central nervous system and in blood. This, as well as the occurrence of central nervous peptide effects after peripheral administration, show the importance of studying the relationships between the peptides in the two compartments. For many peptides, such as the enkephalins, TRH, somatostatin and MIF-1, poor penetration of the blood-brain barrier was shown. In other cases, including beta-endorphin and angiotensin, peptides are rapidly degraded during or just after their entry into brain or cerebrospinal fluid. Some peptides, such as insulin, delta-sleep-inducing peptide, and the lipotropin-derived peptides, enter the cerebrospinal fluid to a slight or moderate extent in the intact form. Many peptide hormones, such as insulin, calcitonin and angiotensin, act directly on receptors in the circumventricular organs, where the blood-brain barrier is absent. Oxytocin, vasopressin, MSH, and an MSH-analog alter the properties of the blood-brain barrier, which may result in altered nutritient supply to the brain. In conclusion, the diffusion of most peptides across the brain vascular endothelium seems to be severely restricted. There are, however, several alternative routes for peripheral peptides to act on the central nervous system. The blood-brain barrier is a major obstacle for the development of pharmaceutically useful peptides, as in the case of synthetic enkephalin-analogs.
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PMID:Minireview. Peptides and the blood-brain barrier. 630 42


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