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PubMed2006

New insights into neuropeptide modulation of aggression: field studies of arginine vasotocin in a territorial tropical damselfish.

The neuropeptides arginine vasotocin (AVT) and arginine vasopressin are key modulators of affiliation and aggression among non-mammalian and mammalian vertebrates, respectively. Here, we explored AVT's effect on aggression in a wild population of beaugregory damselfish, Stegastes leucostictus, a highly territorial species. Aggression by territorial males towards 'intruders' (bottled fishes) was assessed before and after each male received intramuscular injections of either AVT, Manning compound (an AVT V1a receptor antagonist), isotocin (the teleost homologue of mammalian oxytocin differing from AVT by two amino acids) or saline (vehicle control). Compared to saline controls, AVT and Manning increased and decreased aggression, respectively, while isotocin had no effect. Response selectivity was further established in a dose-response study that revealed an inverted U-shaped function. Compared to saline controls, aggression levels for low and high AVT doses were similar, while medium dose treatments were significantly greater. This type of behavioural response, the first that we know of for a vertebrate neuropeptide, could depend on the binding of AVT to both V1-type and other AVT or non-AVT receptors. The pattern revealed here for damselfish may be symptomatic of species- and context-dependent specificity of AVT's modulation of aggression across teleosts, as is currently proposed for tetrapods.

Aggression↗
PubMed1993

Arginine vasotocin gene expression and hormone synthesis during ontogeny of the chicken embryo and the newborn chick.

Chicken embryos at different developmental stages (embryonal day (E) 6 to 21) and chicks at posthatch day 1 (D1) were monitored for the development of their hypothalamo-neurohypophysial system as indicated by the kinetics of arginine vasotocin (AVT) gene expression via mRNA concentration and brain AVT content. Our data concerning the onset of gene expression support previous results from our laboratory and others about an early activation of the AVT gene transcriptional and translational activity around E6. We could detect measurable amounts of AVT in chicken embryo brains at E6 and an exponential increase during further development until D1. Dot blots of hypothalamic RNA extracts indicated that AVT gene transcript concentrations rose between E12 and E17 and slightly dropped thereafter. Northern hybridization showed that this drop was caused by a decrease of full length message and an increase of smaller transcripts during late embryonal and D1 stages, probably an AVT mRNA specific degradation phenomenon. The dissociation between the increase of AVT concentration and AVT mRNA concentration visible at the D1 stage might be due to accumulation and storage of AVT in the magnocellular neurons, preferentially in their axon terminals in the neurohypophysis. Blood samples taken from E14 onwards revealed a constant increase in plasma osmolality and plasma AVT concentration. Our data suggest that, in the chicken, AVT seems to be required early during embryonal development, either for osmoregulatory or further unknown functions.

Animals↗
PubMed1990

Isolation and structure elucidation of bovine pineal arginine vasopressin: arginine vasotocin not identified.

A large number of reports have demonstrated the presence of neurohypophysial hormone-like peptides in mammalian pineal glands and an antigonadotropic function has been ascribed to pineal arginine vasotocin (AVT). We have undertaken large scale purification of bovine pineal neurohypophysial hormone-like substances which demonstrate mouse mammary milk-ejection activity (ME-activity) in vitro. Peptides with ME-activity were extracted from more than 5 kg of bovine pineal glands. ME-activity containing peptides were found in both high (Mr approximately 10,000-15,000) and low (Mr approximately 500-1000) Mr species from Sephadex G-25 chromatography of 0.2 N acetic acid extracts. After ultrafiltration in 5% formic acid, the neurohypophysial hormone-like peptides were localized to an ultrafiltration Mr 500-1000 retentate. A homogeneous peptide, which shared an identical retention time (RT) and amino acid sequence with synthetic 8-arginine vasopressin (AVP), was isolated by serial semipreparative high performance liquid chromatography. On the other hand, the non-mammalian nonapeptide AVT was not identified.

Amino Acid Sequence↗
PubMed1991

Neurophysin-neurohypophyseal hormone interactions: studies using a dansylated vasotocin analogue.

We have synthesized a neurohypophyseal hormone analogue containing an extrinsic fluorescence probe by linking a dansyl (DNS) group to the epsilon-amino group of the lysine at residue 8 of vasotocin. The fluorescence properties of this analogue have been characterized by steady-state and time-resolved spectroscopic methods and compared with those of epsilon-DNS-lysine and the dansylated carboxyl terminal tripeptide Pro-Lys(DNS)-GlyNH2. The binding of this hormone analogue to purified isoforms of bovine neurophysins, the natural carrier proteins of the neurohypophyseal hormones, results in changes in several fluorescence parameters of the dansyl probe. These changes include an increase in intensity and average lifetime, a shift of the emission band to higher energies, and an increase in the emission anisotropy. Anisotropy changes have been used to determine dissociation constants for binding to these neurophysin isoforms. Based on the changes in the fluorescence properties of the dansyl probe, the dansyl group itself interacts with the protein. The degree of the dansyl-neurophysin interaction, however, appears to be different for the full sequence isoform of neurophysin I and the Val89 isoform of neurophysin II.

Amino Acid Sequence↗
PubMed1984

Pineal arginine vasotocin activity increases 200-fold during August in adult rats and hamsters.

In a previous study, measurements of arginine vasotocin-immunoactivity (iAVT) in immature rats over a period of 14 months, led to the discovery of a significant yearly variation, with peak levels of iAVT in August. In the present study, iAVT was measured in pineals obtained from mature male and female rats and hamsters once or twice weekly from July until early September 1982. For all groups, mean pineal AVT-immunoactivity was less that 7 pg/gland in early July, but then increased significantly by August 11-13. For hamsters, maximum values of 1,272 +/- 49 (mean +/- S.E.: n = 3) and 1,065 +/- 62 pg/gland were recorded for males and females, respectively. For rats, peak values measured were 940 +/- 12 pg/gland for males and 1,040 +/- 34 for females. The AVT-activity levels then decreased to less than 100 pg/gland by early September. Thus, a dramatic August elevation of pineal iAVT is characteristic of hamsters as well as rats, and of mature as well as immature animals.

Animals↗
PubMed1978

Effects of the antidiuretic hormone, arginine vasotocin, theophylline, filipin and A23187 on cyclic AMP in isolated frog skin epithelium (Rana temporaria).

A method for measuring cAMP in frog skin epithelium was developed. The epithelia were isolated after collagenase-treatment. cAMP was extracted by boiling water and the extract was purified on dry Al2O3. The change with time of the cAMP level after addition of arginine vasotocin (AVT) was studied. The hormone caused a rapid increase in cAMP level with a maximum after 3-5 min, whereafter the cAMP level declined. Incubation with AVT made the epithelia refractory to a second dose of AVT, which indicates that the decline in cAMP level was caused by a feedback mechanism and not by inactivation of the hormone. cAMP appeared evenly distributed in all cell-layers of the epithelia both before and after stimulation with AVT. Theophylline caused a rapid increase in the cAMP level, which remained elevated for at least 45 min. Addition of the ionophore A23187 or of filipin had no effect on the cAMP level. However, in the presence of theophylline, A23187 enhanced the cAMP level, whereas filipin had no effect. Therefore the involvement of cAMP in the action of A23187 has to be considered.

Animals↗
PubMed1998

Effects of arginine vasotocin, isotocin and melatonin on blood pressure in the conscious atlantic cod (Gadus morhua): hormonal interactions?

The effects of exogenous arginine vasotocin (AVT), isotocin (IT) and melatonin on the blood pressure of conscious Atlantic cod (Gadus morhua) were examined. Ventral aortic blood pressure (PVA) was recorded from a cannula inserted into the afferent branchial artery of the third gill arch. Dorsal aortic blood pressure (PDA) was recorded via a cannula implanted into the efferent branchial artery in the same gill arch. Each fish received two doses (10 and 50 ng kg-1) of AVT, IT and melatonin. AVT was also administered in combination with melatonin. Injection of 10 ng kg-1 AVT produced significant hypertension, especially in animals injected during the daytime. In contrast, the same dose of IT induced no significant change in either PVA or PDA. Administration of 10 ng kg-1 melatonin at night caused a long-lasting decrease in both parameters. Melatonin also inhibited the increase in blood pressure elicited by AVT. These results indicate that AVT, but not IT, is vasopressor in the cod. The effects of combined administration of melatonin and AVT show the antihypertensive action of melatonin in AVT-induced hypertension.

Animals↗
PubMed1983

Avian shell gland contractility: interaction of PGF2 alpha and arginine vasotocin with Ca2+.

The effects of prostaglandin F2 alpha (PGF2 alpha) and arginine vasotocin (AVT) on the isometric contractile activity of avian shell gland longitudinal muscle strips were studied in relation to the role of extracellular Ca2+. PGF2 alpha and AVT stimulated contractile tension in a dose-related manner. This was attenuated when either of the Ca2+ channel blockers verapamil or R33956 was added to the muscle chamber baths. Ca2+-free solution containing 1 mM ethyleneglycol-bis (beta-aminoethylether)-N,N'-tetraacetic acid completely prevented contraction in response to increasing doses of PGF2 alpha or AVT. Washing of the strips with Ca2+-free solution eliminated spontaneous contractile activity, but replenishment of CaCl2 to the medium (0.1-5.0 mM) restored it. Addition of PGF2 alpha to the Ca2+-free medium enhanced contractile tension during Ca2+ replenishment, whereas AVT had no effect on tension generation at low extracellular Ca2+ concentration (0.1-0.5 mM) but increased it at higher extracellular Ca2+ concentration (1.0-5.0 mM). PGF2 alpha stimulation was sensitive to extracellular Na+ concentration, whereas AVT-induced activity was not. Potassium depolarization (20 mM K) potentiated PGF2 alpha-stimulated activity, whereas the response to AVT was unaffected. At 127.5 mM K, AVT-stimulated activity was inhibited. PGF2 alpha-enhanced Ca2+-dependent tension generation was right shifted in a dose-related manner by AVT. These results suggest that extracellular Ca2+ is necessary for the full expression of PGF2 alpha- and AVT-stimulated muscle contraction and suggest that each agonist has a different mechanism of action.

Animals↗
PubMed1995

Amiloride-sensitive and HCO3(-)-dependent ion transport activated by aldosterone and vasotocin in A6 cells.

We studied the effects of aldosterone (Aldo) and arginine vasotocin (AVT) on ion transport of renal epithelial cell line (A6) by measuring short-circuit current (Isc). AVT induced a rapid, transient increase in Isc, followed by a decrease toward the baseline in cells untreated with Aldo. In cells treated with Aldo, Isc showed a biphasic response to AVT, i.e., both transient and sustained increases over 40 min after addition of AVT. The transient increase was composed only of amiloride-insensitive Isc regardless of Aldo treatment, whereas the sustained increase contained both amiloride-sensitive and amiloride-insensitive components. The main part of the amiloride-insensitive, sustained Isc depended on HCO3(-). In cells treated with Aldo for 1 day, removal of HCO3(-) in the bathing solution enhanced the amiloride-sensitive component and decreased the amiloride-insensitive one. These data suggest that 1) Aldo treatment is necessary for an AVT-induced sustained increase of Isc and 2) a HCO3(-)-dependent Isc mainly contributes to the sustained increase in amiloride-insensitive Isc.

Aldosterone↗
PubMed1987

Hydroosmotic responses to short pulses of vasotocin by toad bladder.

When toads, Bufo marinus, were mildly dehydrated, the permeability to water of their urinary bladders increased, but blood samples placed directly on the wall of an isolated assay bladder did not contain enough arginine vasotocin (AVT) to induce the observed response. One explanation for this discrepancy is that AVT is secreted intermittently and rapidly cleared from the blood, even though the hydroosmotic response persists. The hydroosmotic response of bladders to pulsatile secretion of AVT was simulated by dipping isolated bladders for 1 min in Ringer's fluid with AVT followed by washout of hormone. Bladders developed the characteristic increase in membrane permeability to water several minutes after AVT had been removed from the serosal bathing solution. With short periods of bladder exposure to hormone, higher concentrations were required for triggering responses equivalent to those induced with continuous stimulation. This requirement was greater for vasopressin than it was for AVT. Studies with tritium-labeled vasopressin indicated that there is a "receptor reserve" for the hydroosmotic action of vasopressin in the toad bladder. The magnitude of this reserve is reduced as the duration of stimulation with hormone is diminished. It is suggested that pulsatile exposure of the bladder to AVT increases the specificity of the hormone for hydroosmotic receptors and minimizes the development of target organ resistance. The large receptor reserve in this tissue may be required to capture short bursts of AVT secreted into blood, although this remains to be demonstrated.

Animals↗
PubMed2004

Molecular and functional characterization of a vasotocin-sensitive aquaporin water channel in quail kidney.

Both mammals and birds can concentrate urine hyperosmotic to plasma via a countercurrent multiplier mechanism, although evolutionary lines leading to mammals and birds diverged at an early stage of tetrapod evolution. We reported earlier (Nishimura H, Koseki C, and Patel TB. Am J Physiol Regul Integr Comp Physiol 271: R1535-R1543, 1996) that arginine vasotocin (AVT; avian antidiuretic hormone) increases diffusional water permeability in the isolated, perfused medullary collecting duct (CD) of the quail kidney. In the present study, we have identified an aquaporin (AQP) 2 homolog water channel in the medullary cones of Japanese quail, Coturnix coturnix (qAQP2), by RT-PCR-based cloning techniques. A full-length cDNA contains an 822-bp open reading frame that encodes a 274-amino acid sequence with 75.5% identity to rat AQP2. The qAQP2 has six transmembrane domains, two asparagine-proline-alanine (NPA) sequences, and putative N-glycosylation (asparagine-124) and phosphorylation sites (serine-257) for cAMP-dependent protein kinase. qAQP2 is expressed in the membrane of Xenopus laevis oocytes and significantly increased its osmotic water permeability (P(f)), inhibitable (P < 0.01) by mercury chloride. qAQP2 mRNA (RT-PCR) was detected in the kidney; medullary mRNA levels were higher than cortical levels. qAQP2 protein that binds to rabbit anti-rat AQP2 antibody is present in the apical/subapical regions of both cortical and medullary CDs from normally hydrated quail, and the intensity of staining increased only in the medullary CDs after water deprivation or AVT treatment. The relative density of the approximately 29-kDa protein band detected by immunoblot from the medullary cones was modestly higher in water-deprived/AVT-treated quail. The results suggest that 1) medullary CDs of quail kidneys express a mercury-sensitive functioning qAQP2 water channel, and 2) qAQP2 is at least partly regulated by an AVT-dependent mechanism. This is the first clear identification of AQP2 homolog in nonmammalian vertebrates.

Algorithms↗
PubMed2002

Development of an in situ perfused kidney preparation for elasmobranch fish: action of arginine vasotocin.

Acclimation of the European lesser-spotted dogfish Scyliorhinus canicula to reduced environmental salinity [85-70% seawater (SW)] induced a significant diuresis in addition to a significant decrease in plasma osmolality in vivo. The threshold for this diuresis was determined to be 85% SW. Therefore, S. canicula acclimated to 85% SW was selected for further study as a diuretic model in the development of an in situ perfused kidney preparation. The renal role of arginine vasotocin (AVT) in the in situ perfused trunk preparation was investigated. In SW, perfusion of 10(-9) and 10(-10) M AVT resulted in a glomerular antidiuresis and decreases in tubular transport maxima for glucose and perfusate flow. In 85% SW, 10(-10) M AVT had no significant effect on these renal parameters with the exception of transport maxima for glucose and perfusate flow. Tubular parameters remained unchanged by either 10(-9) or 10(-10) M AVT. The results demonstrate that the perfused kidney preparation was a viable tool for the investigation of renal parameters in elasmobranch fish and that AVT induced a glomerular antidiuresis.

Adaptation, Physiological↗
PubMed1986

Osmotic and volemic regulation of plasma arginine vasotocin in conscious domestic fowl.

Recently developed radioimmunoassay methods were utilized to quantitatively characterize secretion of the avian antidiuretic hormone [arginine vasotocin (AVT)] by the hypothalamo-neurohypophyseal system (HNS) of the conscious domestic fowl. The functional characteristics of the osmoreceptor-HNS were evaluated during independent experimental manipulations of extracellular osmolality or volume. Simultaneous measurements of plasma AVT (PAVT) and either plasma osmolality (Posm) or blood volume (BV) in these experiments permitted determination of osmoreceptor sensitivity to independent osmotic or volemic stimuli and set point of the AVT secretory system under conditions of normal hydration. In normally hydrated birds, PAVT and Posm averaged 2.7 +/- 0.2 microU/ml (12.9 +/- 1.0 pg/ml) and 308.1 +/- 0.6 mosmol/kg H2O, respectively (means +/- SE). Characterization of AVT secretion revealed that Posm is a primary determinant of AVT secretion by the HNS of the domestic fowl. Highly correlated and significant relationships between Posm and PAVT exist both above and below the observed basal Posm of normally hydrated birds, with an apparent osmotic threshold for AVT secretion at a Posm of 288.8 mosmol/kg H2O. Analysis of the data also suggested that the HNS is insensitive to changes in BV less than or equal to 10%, because neither isotonic expansion nor reduction of BV altered PAVT. Comparison of past and present avian data with that of the mammalian HNS indicates that 1) the osmotic regulation of antidiuretic hormone secretion is qualitatively and quantitatively similar in birds and mammals, and 2) the volemic regulation of antidiuretic hormone secretion is substantially more important in mammals than in birds.

Animals↗
PubMed1986

Regulation of plasma arginine vasotocin in conscious water-deprived domestic fowl.

Radioimmunoassay methods were employed to quantitatively characterize secretion of the avian antidiuretic hormone [arginine vasotocin (AVT)] by the hypothalamo-neurohypophyseal system (HNS) of the conscious domestic fowl in response to chronic dehydration. Water deprivation permitted characterization of AVT secretion in response to the combined stimuli of extracellular hyperosmolality and hypovolemia; the subsequent repletion of extracellular volume permitted separation of potential osmotic and volemic factors involved in the regulation of AVT secretion. In normally hydrated birds, plasma AVT (PAVT) and plasma osmolality (Posm) averaged 2.2 +/- 0.3 microU/ml (10.5 +/- 1.4 pg/ml) and 309.3 +/- 0.7 mosmol/kg H2O, respectively (means +/- SE). With water deprivation, PAVT and Posm of the birds increased in parallel in a curvilinear manner to maxima of 13.1 +/- 0.6 microU/ml (62.4 +/- 2.9 pg/ml) and 346.6 +/- 2.0 mosmol/kg H2O, respectively, at 96 h of dehydration. The isosmotic repletion of extracellular volume at 96 h by acute intravenous infusion failed to alter 96-h PAVT values. The results indicate that AVT secretion is closely linked to the state of hydration during negative fluid balance in the domestic fowl. Analysis of the data indicated that increases in PAVT that occur with dehydration are mediated primarily by extracellular hyperosmolality and that the HNS of the domestic fowl is relatively insensitive to the simultaneous hypovolemia incurred with fluid deprivation.

Animals↗
PubMed1986

Peripheral angiotensin II stimulates release of vasotocin in conscious chickens.

In mammals, intracranial or peripheral administration of angiotensin II (ANG II) has a number of actions, including the release of antidiuretic hormone (ADH). Relatively little is known of the interactions between the renin-angiotensin and ADH systems in birds. In the present study [Asp1, Val5]ANG II (fowl ANG II) was infused intravenously into conscious White Leghorn cockerels to determine whether peripheral ANG II influences the release of arginine vasotocin (AVT), the avian ADH. Cannulas were inserted into a wing artery and vein under local anesthesia. ANG II was dissolved in 0.154 M NaCl and administered intravenously at 0, 2, 20, and 200 ng X kg-1 X min-1. In a second series of experiments, ANG II was infused in 0.1 and 1.0 M NaCl (200 ng X kg-1 X min-1) to examine the effect of the peptide on osmotic release of ADH. In the three groups administered ANG II in 0.154 M NaCl, plasma AVT before intravenous infusion averaged between 1.8 +/- 0.46 to 2.6 +/- 0.30 microU/ml. In these birds, infusion of ANG II at 2, 20, and 200 ng X kg-1 X min-1 caused plasma AVT to increase over preinfusion means by 39, 78, and 300%, respectively. The changes in AVT occurred in the absence of differences in plasma osmolality, electrolyte composition, or arterial blood pressure among the groups. In chickens that were administered ANG II in 0.1 and 1.0 M NaCl, significantly higher plasma AVT levels were observed compared with a control group receiving the saline infusions alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1987

Dehydration and arginine vasotocin and angiotensin II in CSF and plasma of pekin ducks.

Osmolalities and, by radioimmunoassay, the contents of arginine vasotocin (AVT) and angiotensin II (ANG II) in simultaneously collected cisternal cerebrospinal fluid (CSF) and plasma samples were determined in chronically prepared conscious Pekin ducks (Anas platyrhynchos) adapted to either freshwater (FW ducks) or salt water (2% saline, SW ducks) for drinking. In FW ducks the AVT in CSF was approximately 10-fold higher than in plasma; ANG II concentration in CSF was about two-thirds of that in plasma. In SW ducks concentrations of AVT were increased approximately threefold and of ANG II fourfold in both CSF and plasma. Dehydration in FW ducks (24-48 h) increased AVT and ANG II in both CSF and plasma, the relative rise being greater in plasma. Within 150 min after rehydration plasma AVT fell at unchanged CSF AVT, whereas CSF ANG II fell at unchanged plasma ANG II. Hydration of SW ducks with freshwater had similar effects. The results indicate separate avenues of release of central and systemic AVT and ANG II and support the idea of an independent control of central ANG II as a mediator in osmoregulation, with CSF AVT reflecting the state of osmoregulatory activity of the hypothalamopituitary vasotocinergic system.

Adaptation, Physiological↗
PubMed1988

Glomerular filtration changes during vasotocin-induced antidiuresis in kelp gulls.

In conscious kelp gulls, intravenous infusion of arginine vasotocin (AVT) at rates of 0.03, 0.1, 0.3, and 1.0 ng.kg-1.min-1 resulted in a linear relationship between the log values of the AVT plasma concentrations (measured by radioimmunoassay) and the infusion rates, which indicated a plasma clearance rate for AVT of 15.4 ml.min-1.kg-1 when endogenous AVT formation is considered. Evaluation of the renal actions of AVT at each dose level showed that antidiuresis was consistently associated with reductions in glomerular filtration rate as well as changes in tubule water permeability. Thus the water-conserving action of plasma AVT on the kelp gull kidney involves contributions from both glomerular and tubular mechanisms over the entire physiological range found in these birds.

Animals↗