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PubMed2000

Molecular cloning and functional characterization of a vasotocin receptor subtype that is expressed in the shell gland and brain of the domestic chicken.

In chickens, oviposition is correlated with increased plasma levels of the neurohypophysial hormone vasotocin, and vasotocin stimulates contraction of uterine strips in vitro. A gene encoding a vasotocin receptor subtype that we have designated the VT1 receptor was cloned from the domestic chicken. The open reading frame encodes a 370-amino acid polypeptide that displays seven segments of hydrophobic amino acids, typical of guanine nucleotide-protein-coupled receptors. Other structural features of the VT1 receptor include two potential N-linked glycosylation sites in the extracellular N-terminal region, a conserved aspartic acid in transmembrane domain 2 that is found in nearly all guanine nucleotide-protein-coupled receptors, and two potential protein kinase C phosphorylation sites in the third intracellular loop and C-terminal tail. Expressed VT1 receptors in COS7 cells bind neurohypophysial hormones with the following rank order of potency: vasotocin congruent with vasopressin > oxytocin congruent with mesotocin > isotocin. In addition, the expressed VT1 receptor mediates vasotocin-induced phosphatidylinositol turnover and Ca(2+) mobilization. In the chicken, expression of VT1 receptor gene transcripts is limited to the shell gland (uterus) and the brain. Thus, the VT1 receptor that we have cloned may mediate contractions of the shell gland during oviposition and activate reproductive behaviors known to be stimulated by vasotocin in lower vertebrates.

Amino Acid Sequence↗

PubMed1982

The distribution of vasotocin and isotocin in the brain of the rainbow trout.

The distribution of vasotocin and isotocin in the brain of the rainbow trout Salmo gairdneri was investigated by the unlabeled antibody enzyme method, by using purified antisera against arginine vasotocin and isotocin. In the preoptic nucleus no clear differences were observed in the distribution of vasotocin- and isotocin-containing cells. Vasotocin and isotocin innervation was found in most brain regions, though in general isotocin fibers were much more abundant. The area dorsalis pars medialis of the telencephalon, the saccus dorsalis, and the basal part of the nucleus recessus posterioris were found to be innervated by vasotocin and scarcely by isotocin fibers. In the nucleus habenularis, the nucleus recessus lobus lateralis, the nucleus preglomerulosus pars medialis, and the tectum mesencephali isotocin fibers prevailed. These findings in the trout brain are compared with the vasopressin and oxytocin innervation of the rat brain.

Animals↗

PubMed1993

Effects of central and peripheral administration of arginine vasotocin and related neuropeptides on blood pressure and heart rate in the conscious trout.

The cardiovascular activity of neurohypophyseal peptides has been investigated in conscious trout bearing an intracerebroventricular guide cannula and a permanent intraarterial catheter. Changes in diastolic pressure, systolic pressure and heart rate were monitored during the 25-min period following intracerebroventricular or intraarterial administration of arginine vasotocin and related neuropeptides, including arginine vasopressin, oxytocin, hydrin-2, mesotocin, isotocin and conopressin-S. Intracerebroventricular injection of increasing doses of arginine vasotocin (0.62-5 pmol) induced a dose-dependent increase of diastolic and systolic pressures. The onset of the response occurred within 3-5 min after intracerebroventricular administration of arginine vasotocin and the maximal increase was reached at 10-15 min. Central administration of vasopressin and oxytocin induced a significant rise in diastolic and systolic pressures at a dose of 5 pmol while hydrin-2 only caused a significant elevation of blood pressure at a dose of 50 pmol. Central administration of mesotocin, isotocin and conopressin-S (5-500 pmol each) had no significant effect on blood pressure. No changes in heart rate occurred after intracerebroventricular injection of any of the seven neuropeptides tested. Intraarterial injection of arginine vasotocin (50 pmol) induced a significant rise in blood pressure and bradycardia. Peripheral injection of the other neuropeptides did not cause any modification of the cardiovascular activity, whatever the doses administered (5-500 pmol). The V1A receptor antagonist [d(CH2)5, Tyr(OMe)2]arginine vasopressin had no intrinsic effect on blood pressure and heart rate when injected centrally (50 pmol) or in the peripheral circulation (200 pmol). At the same doses, [d(CH2)5, Tyr(OMe)2]arginine vasopressin reduced by 50 and 66%, respectively, the increase in blood pressure evoked by intracerebroventricular (5 pmol) or intraarterial (50 pmol) injections of arginine vasotocin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1984

Immunological and biological characteristics of the vasotocin-like activity in the head ganglia of gastropod molluscs.

Extracts of cerebral and pleuro-pedal ganglia from two terrestrial slugs, Ariolimax columbianus and Limax maximus, and from the marine opisthobranch, Aplysia californica, contain immunoreactivity resembling that of a vasotocin or vasopressin. Radioimmunoassays using several antisera indicate that the immunoreactivity is not due to vasotocin, vasopressin, or any other known naturally occurring neurohypophyseal peptide. Immunoreactivity of extracts on a relatively nonspecific vasopressin antiserum is well correlated with activity on antidiuretic assays on rats. Both immunoreactivity and antidiuretic activity are adsorbed onto bovine neurophysin affinity columns. Thus these extracts contain one or more peptides that closely resemble the vertebrate antidiuretic hormones, vasotocin and vasopressin, both immunologically and pharmacologically. The amounts of immunoreactivity and antidiuretic activity in ganglion extracts do not appear to change during dehydration and rehydration. Although both ganglionic extracts and vasotocin stimulate exudation of fluid across the slug body wall, the present experiments provide no evidence that the vasotocin-like material(s) in these ganglia may participate as neurotransmitters or hormones in the regulation of fluid balance. This remains an attractive hypothesis.

Animals↗

PubMedDate not supplied

Distribution of immunoreactive mesotocin and vasotocin in the brain and pituitary of chickens.

The distribution of vasotocin and mesotocin in the pituitary and central nervous system in male chickens was determined using radioimmunoassays. Neither peptide was detected in the pineal. Mesotocin, but not vasotocin, was detected in the cerebellum. Both peptides were found in the septal area, archistriatum, paleostriatum, optic lobe, anterior, medial and posterior hypothalamus, midbrain, pons, medulla oblongata, and the anterior and posterior pituitary. Equal amounts of the 2 peptides were present in the septal area, archistriatum and anterior hypothalamus whereas vasotocin was more abundant (2- to 10-fold) in the paleostriatum, optic lobe, midbrain, and pituitary. The amount of mesotocin was about twice that of vasotocin in the medulla oblongata and the medial and posterior hypothalamus. The wide distribution of vasotocin and mesotocin in extrahypothalamic sites in the central nervous system suggests that the peptides may, as in mammals, have a role in a variety of autonomic and endocrine regulatory processes in chickens.

Animals↗

PubMedDate not supplied

Effect of peripheral administration of arginine vasotocin on neonatal sleep in rats.

Vasotocin was recently reported to increase the neonatal amount of active sleep in kittens. In this study we examined the effects of arginine vasotocin (vasotocin), given intraperitoneally and at a wide dose range, on the sleep-wake behavior of 7-day-old and 14-day-old rat pups using a static charge sensitive recording system. It increased the percentage of quiet state relative to total sleep time at the doses of 0.01-1.0 ng/g of body weight but did not affect it at the dose of 0.001 ng/g. The percentage of active sleep was decreased by doses of 0.01-10.0 ng/g. The increase in the amount of quiet state and the concurrent suppression of active sleep lasted for 6 hours. Wakefulness was slightly increased at 10 ng/g of vasotocin. These findings indicate that, in contrast to the reports on kittens, in newborn rats peripheral administration of vasotocin increases the amount of quiet state relative to total sleep time and decreases that of active sleep.

Aging↗

PubMedDate not supplied

The hypothalamo-hypophyseal system of the white seabream Diplodus sargus: immunocytochemical identification of arginine-vasotocin, isotocin, melanin-concentrating hormone and corticotropin-releasing factor.

The distribution of the neurosecretory hormones vasotocin, isotocin and melanin-concentrating hormone and the hypophysiotropic hormone corticotropin-releasing factor was studied in the hypothalamo-hypophyseal system of the white seabream (Diplodus sargus) using immunocytochemical techniques. Magnocellular and parvocellular perikarya immunoreactive for arginine-vasotocin and isotocin were present in the nucleus preopticus. Perikarya immunoreactive for arginine-vasotocin extended more caudally with respect to isotocin-immunoreactive perikarya. Parvocellular perikarya were located at rostroventral levels and magnocellular perikarya in the dorsocaudal portion of the nucleus. Arginine-vasotocin and isotocin did not coexist in the same neuron. Fibres immunoreactive for arginine-vasotocin and isotocin innervated all areas of neurohypophysis and terminate close to corticotropic and melanotropic cells. Perikarya immunoreactive for melanin-concentrating hormone and corticotropin-releasing factor were observed in the nucleus lateralis tuberis, with a few neurons in the nucleus periventricularis posterior. In addition, melanin-concentrating hormone immunoreactive perikarya were detected in the nucleus recessus lateralis. The preoptic nucleus did not show immunoreactivity for these antisera. Fibres showing melanin-concentrating hormone and corticotropin-releasing factor immunoreactivity ended close to the melanotropic and somatolactotrophic cells of the pars intermedia, and close to the corticotrophic cells of the rostral pars distalis.

Animals↗

PubMed1989

Hydrins, hydroosmotic neurohypophysial peptides: osmoregulatory adaptation in amphibians through vasotocin precursor processing.

From neurointermediate pituitary glands of Xenopus laevis and Rana esculenta, previously unreported peptides termed hydrins, active on water permeability of frog urinary bladder and frog skin (Brunn or "water-balance" effect), have been isolated and sequenced. These peptides seem to be derived from the pro-vasotocin-neurophysin precursor. Hydrin 1, found in Xenopus, has been identified as vasotocin C-terminally extended with the Gly-Lys-Arg sequence; hydrin 2, found in Rana, has been identified as vasotocin C-terminally extended with glycine. Hydrin 2 has been detected in several Ranidae (R. esculenta, Rana temporaria, Rana pipiens) and Bufonidae (Bufo bufo, Bufo ictericus) and appears to have a large distribution in terrestrial or semiaquatic anurans. Hydrins, in contrast to vasotocin, are not active on rat uterus or rat blood pressure. They are absent from other vasotocin-bearers such as birds and could be involved specifically in water-electrolyte regulation of amphibians.

Acclimatization↗

PubMed1996

Mutational analysis and molecular modeling of the nonapeptide hormone binding domains of the [Arg8]vasotocin receptor.

To identify determinants that form nonapeptide hormone binding domains of the white sucker Catostomus commersoni [Arg8]vasotocin receptor, chimeric constructs encoding parts of the vasotocin receptor and parts of the isotocin receptor have been analyzed by [(3,5-3H)Tyr2, Arg8]vasotocin binding to membranes of human embryonic kidney cells previously transfected with the different cDNA constructs and by functional expression studies in Xenopus laevis oocytes injected with mutant cRNAs. The results indicate that the N terminus and a region spanning the second extracellular loop and its flanking transmembrane segments, which contains a number of amino acid residues that are conserved throughout the nonapeptide receptor family, contribute to the affinity of the receptor for its ligand. Nonapeptide selectivity, however, is mainly defined by transmembrane region VI and the third extracellular loop. These results are complemented by a molecular model of the vasotocin receptor obtained by aligning its sequence with those of other G-protein coupled receptors as well as that of bacteriorhodopsin. The model indicates that amino acid residues of transmembrane regions II-VII that are located close to the extracellular surface also contribute to the binding of vasotocin.

Amino Acid Sequence↗

PubMed1989

Synthesis and characterization of fluorescein- and rhodamine-labeled probes for vasotocin receptors.

Fluorescent analogues of vasotocin, [1-(beta-mercaptopropionic acid), 9-(p-aminofluoresceinylphenylalanine)]arginine vasotocin [[MPA1, (p-NH2flu)Phe9]AVT] and [1-(beta'-mercaptopropionic acid), 9-(p-amino rhodaminylphenylalanine)]AVT [[MPA1, (p-NH2rhod)-Phe9]AVT], were synthesized by the solid-phase method. These compounds yielded half-maximal hydrosmotic responses (half-maximal values) in the toad urinary bladder at 2 X 10(-9) M. Epifluorescence microscopy showed punctate basal localization of analogues on the majority of bladder epithelial cells within 20 min. The cellular localization was prevented by vasotocin. These fluorescent analogues may serve as useful probes for vasotocin receptors in toad bladder and in tissues from other species that use vasotocin as their antidiuretic-pressor hormone.

Amino Acid Sequence↗

PubMed1979

Suppression of the luteinizing hormone releasing effect of luteinizing hormone releasing hormone by arginine-vasotocin.

The concentrations of 17-oxosteroids in the spermatic venous blood of anaesthetized dogs were used as an index of LH release to assess the effects of arginine-vasotocin on the response of the canine pituitary gland to exogenous luteinizing hormone releasing hormone (LH-RH). When injected into the carotid artery, arginine-vasotocin (1.0 microgram/kg body wt) caused no significant alterations in the testicular output of 17-oxosteroids. The administration of LH-RH (5 microgram/kg body wt, a standard dose) into the carotid artery produced typical stimulation of testicular 17-oxosteroid secretion. Administration of arginine-vasotocin (0.01, 0.1 or 1.0 microgram/kg body wt) into the carotid artery 3 h before the administration of a standard dose of LH-RH inhibited the testicular secretion of 17-oxosteroids normally induced by LH-RH. However, pretreatment with arginine-vasotocin (1.0 microgram/kg body wt) did not affect the testicular response to i.v. administration of human chorionic gonadotrophin (5 i.u./kg body wt). These results indicate that in the dog, arginine-vasotocin inhibits the LH-RH-induced release of LH by acting acting directly on the anterior pituitary gland.

17-Ketosteroids↗

PubMed1992

Effect of FSH, LH, LH-RH and arginine-vasotocin on the production of steroids, nonapeptide hormones and cGMP by rabbits granulosa cells isolated at different stages of reproductive cycle.

Granulosa cells isolated from ovaries of non-cycling, cycling and pregnant rabbits of the same age were cultured in vitro either without or with pFSH (1 micrograms/ml), bLH (1 IU/ml), LH-RH (25 ng/ml) or arginine-8-vasotocin (100 ng/ml). The production of immunoreactive progesterone, estradiol-17 beta, oxytocin, arginine-8-vasopressin and cGMP was analyzed. The gonadotropins did not show any significant effects on the cells isolated from non-cycling and cycling rabbits, but not from these of pregnant ones. LH-RH inhibited and vasotocin stimulated progesterone production. All hormones used stimulated estradiol release from cells of non-cycling rabbits, while in a case of cycling animals no change was found. In the cell from pregnant females the release of estradiol was enhanced after LH treatment only. The treatment with FSH and LH (but not with LH-RH or vasotocin) resulted in a remarkable rise of granulosa vasopressin surge irrespectively to the reproductive stage. Oxytocin production by granulosa cells incubated either without or with LH, LH-RH or vasotocin was undetectable. However, FSH strongly stimulated oxytocin release. FSH and in lesser extent, LH or LH-RH (but not vasotocin) activated granulosa cGMP production in the cells from cycling and pregnant (but not from non-cycling) animals. It was also found that, in contrast to other reproductive stages, basal progesterone release from the cells of pregnant rabbits was increased, while in a case of non-cycling animals the basal estradiol release was decreased and that of cGMP was increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

[Water homeostasis in amphibia: vasotocin and hydrins].

Water homeostasis is ensured in vertebrates through neuroendocrine reflexes involving hormones and specialized exchange organs depending whether the habitat is freshwater, sea or land. Amphibians have a development recapitulating two adaptive programs, first a freshwater fish program as a tadpole, then a land vertebrate program as an adult. The second, however, is imperfect because of the great evaporative water loss through the skin when the animal is in the open air. This loss must be compensated by water reabsorption through the nephron, the urinary bladder and mainly by water uptake through the skin. Water reabsorption by the nephron is not as efficient as in higher vertebrates but water uptake through the skin is crucial because adult amphibians, like tadpoles, do not drink. Adaptation occurred at the level of three organs, nephron, urinary bladder and skin whose permeability is under control of specific hormones. Aside from vasotocin, active on these three organs, differential maturation of provasotocin led to processing-arrested intermediates, namely vasotocinyl-Gly in virtually all anuran amphibians and vasotocinyl-Gly-Lys-Arg in Xenopus laevis. These intermediates result from a down regulation of the alpha-amidating enzyme or carboxypeptidase E, respectively. They have been termed hydrin 2 and hydrin 1 because they are endowed with hydroosmotic properties equal or superior to those of vasotocin on the skin and the bladder. However, in contrast to vasotocin, they are devoid of antidiuretic activity. Adaptive evolution has created, aside from the osmoregulatory vasotocin-nephron system that was preserved in strictly terrestrial nonmammalian tetrapods, additional functions such as the hydrin-skin and the hydrin-bladder rehydrations with specific messengers and organs. The adjuvant systems disappeared in true land vertebrates because the vasotocin-nephron system became more efficient.

Amphibians↗

PubMed1997

Adaptive evolution of water homeostasis regulation in amphibians: vasotocin and hydrins.

Volemia and osmolality homeostasis is ensured in vertebrates through neuroendocrine reflexes, involving an afferent neural branch from baro- and osmo-receptors to hypothalamus and an efferent endocrine branch from secretory neurons to target hydroosmotic cells equipped with receptors and effectors. Whereas the osmoregulatory system in the tadpole comprises three organs, namely gut, kidney and gills, as in freshwater fishes, the adult displays a quaternary strategy with gut, kidney, urinary bladder and skin. In particular, the cutaneous permeability entails a great evaporative water loss when the animal is in the open air, loss that must be compensated by water reabsorption through the nephron and the urinary bladder and mainly by water uptake through the skin. Adaptation occurred at the level of these organs by regulation of their permeability through neurohypophysial hormones. Aside from vasotocin, active on the three organs, all anuran Amphibia possess hydrin 2 (vasotocinyl-Gly), a peptide resulting from a down-regulation of provasotocin processing. Exceptionally Xenopus laevis, a permanent aquatic toad, has hydrin 1 (vasotocinyl-Gly-Lys-Arg) instead of hydrin 2. Hydrins are somewhat more active than vasotocin on water permeation of skin and bladder but are devoid of antidiuretic activity. Adaptive evolution has created, along with the vasotocin-nephron system, preserved in all terrestrial non-mammalian tetrapods, additional functions such as the hydrin-skin and hydrin-bladder rehydration mechanisms. Specific hydrin receptors might exist in the skin and the bladder, different from those of vasotocin in the kidney. It is assumed that the water channel recruitment mechanism, found for vasopressin acting on the collecting duct principal cells in mammals, is also involved when vasotocin and hydrins stimulate their hydroosmotic target cells and that hormone-regulated aquaporin 2-like proteins could be identified in the three osmoregulatory organs of amphibians.

Adaptation, Physiological↗

PubMed1997

Appearance of an arginine vasotocin receptor of large molecular size in the uterus (shell gland) of the hen at oviposition.

The molecular mass of the arginine vasotocin receptor in membrane fractions of the uterus (shell gland) of hens was estimated by autoradiography of [125I]-labelled arginine vasotocin binding protein after SDS-PAGE. A band of approximately 67 kDa was found in all of the samples taken from laying hens before and after oviposition and from nonlaying hens. In addition to this band, another band of approximately 95 kDa was found in samples from laying hens taken immediately before and after oviposition. Both bands were reduced by the presence of unlabelled arginine vasotocin or mesotocin, but the reduction was greater by arginine vasotocin than by mesotocin. These two bands were not reduced by chicken luteinizing hormone-releasing hormone-I (Gln8-GnRH), chicken luteinizing hormone-releasing hormone-II (His5,Trp7,Tyr8-GnRH) and chicken angiotensin-II (Val5-angiotensin-II). The appearance of the arginine vasotocin receptor of the larger molecular size may be related to oviposition in hens.

Analysis of Variance↗

PubMed1980

The topography of mesotocin and vasotocin systems in the brain of the domestic mallard and Japanese quail: immunocytochemical identification.

The neurosecretory systems producing mesotocin (MT) and vasotocin (VT) (the avian homologues of oxytocin and vasopressin, respectively) were characterized in the brains of the domestic mallard and Japanese quail by means of indirect immunofluorescence techniques using specific antisera. In the anterior preoptic region, including the organum vasculosum of the lamina terminalis, and at different levels of the supraoptic and paraventricular nuclei, separate mesotocin- and vasotocin-producing neurons were identified. Mesotocinergic and vasotocinergic neurons were also located in the tuberomammillary area, among the ectomammillary tract fibers. The supraoptico-neurohypophysial tract, formed by vasotocin- and mesotocin-containing axons, enters the internal zone of the median eminence and ends in the posterior lobe of the pituitary. The external zone of the rostral median eminence appears to contain vasotocin and mesotocin fibers, which terminate in close contact with the capillaries of the hypophysial portal system.

Animals↗

PubMedDate not supplied

Vasopressin and vasotocin facilitate reversal of a brightness discrimination.

Male albino rats received vasopressin, vasotocin, pressinoic acid or placebo and were tested on an aversively motivated brightness discrimination task. Treatment with both vasopressin and vasotocin had no effect on acquisition but facilitated the reversal of the discrimination. Pressinoic acid had an inconsistent effect. The results are interpreted to show that the C terminal of the peptides vasopressin and vasotocin influence potency of these peptides. Furthermore, the results are interpreted as showing that both vasotocin and vasopressin influence selective attention during aversively motivated tasks.

Animals↗

PubMed1993

Vasotocin and hydrin 2 (vasotocinyl-Gly) in the African toad Bufo regularis: study under various environmental conditions.

1. The neurohypophysial osmoregulatory hormones of the African toad Bufo regularis, a species adapted to estivate under dry and hot conditions, have been investigated. Vasotocin and hydrin 2 (vasotocinyl-Gly) have been identified by their retention times in high-pressure reverse-phase liquid chromatography and coelution with synthetic peptides, their pharmacological properties (vasotocin) and microsequencing. 2. Vasotocin-associated neurophysin (MSEL-neurophysin type) has been characterized by its N-terminal amino acid sequence. 3. In toads subjected to dehydration by evaporation (20% weight loss) or to osmotic stress by immersion in 2% NaCl for 3 hr (6% weight loss), the molar ratio hydrin 2/vasotocin (about 2:1) remained similar to the one observed in control animals. 4. In toads exposed to saline solution, there was a large decrease (roughly 30%) in the amounts of both hormones in the neuro-hypophysis. Environmental conditions for distinct secretions of vasotocin and hydrin 2 remain to be found.

Amino Acid Sequence↗